Professor Joseph Keddie

Professor of Soft Matter Physics
MS, PhD (Cornell University, USA); BA, BS (Alfred University, USA)

Academic and research departments

Department of Physics.


Areas of specialism

Soft matter physics, with a special interest in waterborne colloids and polymer thin films; Techniques to probe soft matter include NMR profiling and diffusometry, ellipsometry, and ion beam analysis, along with a range of microscopies.; Applications of colloids in adhesives, coatings and nanocomposites

University roles and responsibilities

  • Senator representing the Faculty of Engineering and Physical Sciences
  • Senior Tutor for Professional Training for Physics

    My qualifications

    PhD in Materials Science and Engineering
    Cornell University (USA)
    MS in Materials Science and Engineering
    Cornell University (USA)
    BS in Ceramic Engineering
    BA in English
    Alfred University (USA)

    Business, industry and community links

    Chemicals, polymers, and coatings industry
    Consultant to industry on film formation and applications of polymer colloids; presenter of workshops for training


    Research interests

    Research collaborations

    Indicators of esteem

    My teaching

    My publications


    • Our paper in Physical Review Letters on "Dynamic Stratification in Drying Films of Colloidal Mixtures," has an Altmetric score of 689 (in the 99th percentile for publications of a similar age). We report our discovery a mechanism for stratification in which small colloidal particles accumulate on a layer of larger particles.


    CA Mills, A Intaniwet, M Shkunov, JL Keddie, PJ Sellin (2009)Flexible radiation dosimeters incorporating semiconducting polymer thick films, In: Proceedings of SPIE - The International Society for Optical Engineering7449

    Flexible radiation dosimeters have been produced incorporating thick films (>1 μm) of the semiconducting polymer poly([9,9-dioctylfluorenyl-2,7-diyl]-co-bithiophene). Diode structures produced on aluminium-metallised poly(imide) substrates, and with gold top contacts, have been examined with respect to their electrical properties. The results suggest that a Schottky conduction mechanism occurs in the reverse biased diode, with a barrier to charge injection at the aluminium electrode. Optical absorption/emission spectra reveal a band gap of 2.48 eV for the polymer. The diodes have been used for direct charge detection of 17 keV X-rays, generated by a molybdenum source. Using operating voltages of -10 and -50 V respectively, sensitivities of 54 and 158 nC/mGy/cm3 have been achieved. Increasing the operating voltage shows that the diodes are stable up to approximately -200 V without significant increase in the dark current of the device (

    E Gonzalez, M Paulis, M Jesus Barandiaran, JL Keddie (2013)Use of a Routh-Russel Deformation Map To Achieve Film Formation of a Latex with a High Glass Transition Temperature, In: LANGMUIR29(6)pp. 2044-2053 AMER CHEMICAL SOC
    F Deplace, MA Rabjohns, T Yamaguchi, AB Foster, C Carelli, C-H Lei, K Ouzineb, JL Keddie, PA Lovell, C Creton (2009)Deformation and adhesion of a periodic soft-soft nanocomposite designed with structured polymer colloid particles, In: Soft Matter5(7)pp. 1440-1447 Royal Society of Chemistry
    FA Boroumand, M Zhu, AB Dalton, JL Keddie, PJ Sellin, JJ Gutierrez (2007)Direct x-ray detection with conjugated polymer devices, In: APPLIED PHYSICS LETTERS91(3)ARTN 0pp. ?-? AMER INST PHYSICS
    FT Carter, RM Kowalczyk, I Millichamp, M Chainey, Joseph Keddie (2014)Correlating Particle Deformation with Water Concentration Profiles during Latex Film Formation: Reasons That Softer Latex Films Take Longer to Dry, In: LANGMUIR30(32)pp. 9672-9681 AMER CHEMICAL SOC
    A Intaniwet, CA Mills, M Shkunov, PJ Sellin, JL Keddie (2012)Heavy metallic oxide nanoparticles for enhanced sensitivity in semiconducting polymer x-ray detectors, In: Nanotechnology23(23)235502pp. ?-? IOP Publishing

    Semiconducting polymers have previously been used as the transduction material in x-ray dosimeters, but these devices have a rather low detection sensitivity because of the low x-ray attenuation efficiency of the organic active layer. Here, we demonstrate a way to overcome this limitation through the introduction of high density nanoparticles having a high atomic number (Z) to increase the x-ray attenuation. Specifically, bismuth oxide (Bi O ) nanoparticles (Z=83 for Bi) are added to a poly(triarylamine) (PTAA) semiconducting polymer in the active layer of an x-ray detector. Scanning electron microscopy (SEM) reveals that the Bi O nanoparticles are reasonably distributed in the PTAA active layer. The reverse bias dc currentvoltage characteristics for PTAABi O diodes (with indium tin oxide (ITO) and Al contacts) have similar leakage currents to ITO/PTAA/Al diodes. Upon irradiation with 17.5keV x-ray beams, a PTAA device containing 60wt% Bi O nanoparticles demonstrates a sensitivity increase of approximately 2.5 times compared to the plain PTAA sensor. These results indicate that the addition of high-Z nanoparticles improves the performance of the dosimeters by increasing the x-ray stopping power of the active volume of the diode. Because the Bi O has a high density, it can be used very efficiently, achieving a high weight fraction with a low volume fraction of nanoparticles. The mechanical flexibility of the polymer is not sacrificed when the inorganic nanoparticles are incorporated. © 2012 IOP Publishing Ltd.

    M Goikoetxea, Y Reyes, CM de las Heras Alarcón, RJ Minari, I Beristain, M Paulis, MJ Barandiaran, JL Keddie, JM Asua (2012)Transformation of waterborne hybrid polymer particles into films: Morphology development and modeling, In: Polymer53(5)pp. 1098-1108 Elsevier

    Films cast from multiphase polymer particles have the potential to combine the properties of their components synergistically. The properties of the film depend on the hybrid polymer architecture and the film morphology. However, how the polymer microstructure and particle morphology are transformed during film formation to determine the film morphology is not well understood. Here, using waterborne alkyd-acrylic nanocomposite particles in a case study, it was found that phase migration leading to the formation of aggregates occurred during film formation. A coarse-grained Monte Carlo model was developed to account for the effects of polymer microstructure and particle morphology on the morphology of the film. The model was validated by comparing its predictions with the observed effects, and then used to explore combinations of polymer microstructure and particle morphology not attainable with the system used as a case study. Significantly, the compatibility of the phases was found to have a greater influence than the morphology of the particles in determining the film structure.

    Izabela Jurewicz, Alice A.K King, Ravi Shanker, Matthew J. Large, Roman J. Smith, Ross Maspero, Sean P. Ogilvie, Jurgen Scheerder, Jun Han, Claudia Backes, Joe Razal, Marian Florescu, Joseph Keddie, Jonathan N. Coleman, Alan Dalton (2020)Mechanochromic and Thermochromic Sensors Based on Graphene Infused Polymer Opals, In: Advanced Functional Materials30(31) Wiley

    High quality opal-like photonic crystals containing graphene are fabricated using evaporation-driven self-assembly of soft polymer colloids. A miniscule amount of pristine graphene within a colloidal crystal lattice results in the formation of colloidal crystals with a strong angle-dependent structural color and a stop band that can be reversibly shifted across the visible spectrum. The crystals can be mechanically deformed or can reversibly change color as a function of their temperature, hence their sensitive mechanochromic and thermochromic response make them attractive candidates for a wide range of visual sensing applications. In particular, we show that the crystals are excellent candidates for visual strain sensors or integrated time-temperature indicators which act over large temperature windows. Given the versatility of these crystals, this method represents a simple, inexpensive and scalable approach to produce multifunctional graphene infused synthetic opals and opens up exciting applications for novel solution-processable nanomaterial based photonics.

    AADT Adikaari, JD Carey, V Stolojan, JL Keddie, SRP Silva (2006)Bandgap enhancement of layered nanocrystalline silicon from excimer laser crystallization, In: NANOTECHNOLOGY17(21)pp. 5412-5416 IOP PUBLISHING LTD

    Excimer laser irradiation is used to crystallize hydrogenated amorphous silicon thin films. The resulting films show a stratified microstructure with a crystalline volume fraction of up to 90%. There is a range of excimer laser energy that can produce stratified nanocrystalline silicon with a Tauc gap as high as 2.2 eV. This value is greater than that of amorphous or crystalline silicon and is contrary to that predicted from the theoretical analysis of mixed-phase silicon thin films. The phenomenon is explained by employing transmission electron microscopy and spectroscopic ellipsometry, and the observed bandgap enhancement is associated with quantum confinement effects within the nanocrystalline silicon layers, rather than an impurity variation.

    Véronique Dehan, Elodie Bourgeat-Lami, Franck D'Agosto, Brendan Duffy, Andrea Fortini, Sharon Hilton, Kalliopi Krassa, Joseph Keddie, Ming L. Koh, Muriel Lansalot, Michelle Lee, Jennifer Lesage de la Haye, Ignacio Martin-Fabiani, Christos Mantzaridis, Douglas P. Mazeffa, Richard Sear, Malin Schulz, Morgan Sibbald, Brian Skerry, Brett Thomas (2017)High-performance water-based barrier coatings for the corrosion protection of structural steel, In: Steel Construction10(3)pp. 254-259 Ernst und Sohn

    This article provides an overview of the outcomes of a European-funded project called BarrierPlus. A new type of water-based barrier coating was developed for structural steel applications. The advantages of this coating include enhanced moisture resistance, low volatile organic compounds (VOCs) and one-component self-crosslinking free of isocyanates. To enable this performance, a latex polymer binder was uniquely designed without using soap-like molecules, known as surfactants, to form the dispersion. By minimizing surfactants in the coating, the barrier properties were significantly enhanced. The latex was successfully scaled up to 15 kg quantities by an SME, coating formulations were scaled to pilot quantities and a variety of characterization and coating performance tests were completed. A life cycle assessment found that the BarrierPlus coating has a better environmental profile than an industry benchmark solvent-borne coating and showed promising results relative to commercial waterborne benchmarks.

    Y Liu, AM Gajewicz, V Rodin, W-J Soer, J Scheerder, G Satgurunathan, Peter McDonald, Joseph Keddie (2016)Explanations for Water Whitening in Secondary Dispersion and Emulsion Polymer Films, In: Journal of Polymer Science, Part B: Polymer Physics54(16)pp. 1658-1674 Wiley

    The loss of optical transparency when polymer films are immersed in water, which is called “water whitening,” severely limits their use as clear barrier coatings. It is found that this problem is particularly acute in films deposited from polymers synthesized via emulsion polymerization using surfactants. Water whitening is less severe in secondary dispersion polymers, which are made by dispersing solution polymers in water without the use of surfactants. NMR relaxometry in combination with optical transmission analysis and electron microscopy reveal that some of the water sorbed in emulsion polymer films is contained within nano-sized “pockets” or bubbles that scatter light. In contrast, the water in secondary dispersion polymer films is mainly confined at particle interfaces, where it scatters light less strongly and its molecular mobility is reduced. The addition of surfactant to a secondary dispersion creates a periodic structure that displays a stop band in the optical transmission. The total amount of sorbed water is not a good indicator of polymers prone to water whitening. Instead, the particular locations of the water within the film must be considered. Both the amount of water and the size of the local water regions (as are probed by NMR relaxometry) are found to determine water whitening.

    I Jurewicz, AAK King, P Worajittiphon, P Asanithi, EW Brunner, RP Sear, TJC Hosea, JL Keddie, AB Dalton (2010)Colloid-Assisted Self-Assembly of Robust, Three-Dimensional Networks of Carbon Nanotubes over Large Areas, In: MACROMOLECULAR RAPID COMMUNICATIONS31(7)pp. 609-615 WILEY-V C H VERLAG GMBH
    CA Mills, H Al-Otaibi, A Intaniwet, M Shkunov, S Pani, JL Keddie, PJ Sellin (2013)Enhanced x-ray detection sensitivity in semiconducting polymer diodes containing metallic nanoparticles, In: Journal of Physics D: Applied Physics46(27)275102pp. ?-? Institute of Physics

    Semiconducting polymer X-radiation detectors are a completely new family of low-cost radiation detectors with potential application as beam monitors or dosimeters. These detectors are easy to process, mechanically flexible, relatively inexpensive, and able to cover large areas. However, their x-ray photocurrents are typically low as, being composed of elements of low atomic number (Z), they attenuate x-rays weakly. Here, the addition of high-Z nanoparticles is used to increase the x-ray attenuation without sacrificing the attractive properties of the host polymer. Two types of nanoparticles (NPs) are compared: metallic tantalum and electrically insulating bismuth oxide. The detection sensitivity of 5 µm thick semiconducting poly([9,9-dioctylfluorenyl-2,7-diyl]-co-bithiophene) diodes containing tantalum NPs is four times greater than that for the analogous NP-free devices; it is approximately double that of diodes containing an equal volume of bismuth oxide NPs. The x-ray induced photocurrent output of the diodes increases with an increased concentration of NPs. However, contrary to the results of theoretical x-ray attenuation calculations, the experimental current output is higher for the lower-Z tantalum diodes than the bismuth oxide diodes, at the same concentration of NP loading. This result is likely due to the higher tantalum NP electrical conductivity, which increases charge transport through the semiconducting polymer, leading to increased diode conductivity.

    Nicolas, Van Luc Busatto, Vlad Stolojan, M Shaw, Joseph Keddie, Peter Roth (2018)Reactive Polymorphic Nanoparticles: Preparation via Polymerization-induced Self-assembly and Post-synthesis Thiol–para-Fluoro Core Modification, In: Macromolecular Rapid Communications Wiley-VCH Verlag

    The use of 2,3,4,5,6-pentafluorobenzyl methacrylate (PFBMA) as a core-forming monomer in ethanolic RAFT dispersion polymerization formulations is presented. Poly[poly(ethylene glycol) methyl ether methacrylate] (pPEGMA) macromolecular chain transfer agents were chain extended with PFBMA leading to nanoparticle formation via polymerization-induced self-assembly (PISA). pPEGMA-pPFBMA particles exhibited the full range of morphologies (spheres, worms, and vesicles) including pure and mixed phases. Worm phases formed gels that underwent a thermo-reversible degelation and morphological transition to spheres (or spheres and vesicles) upon heating. Post-synthesis, the pPFBMA cores were modified through thiol–para-fluoro substitution reactions in ethanol using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as the base. For monothiols, conversions were 64% (1-octanethiol) and 94% (benzyl mercaptan). Spherical and worm-shaped nano-objects were core cross-linked using 1,8-octanedithiol, which prevented their dissociation in non-selective solvents. For a temperature-responsive worm sample, cross-linking additionally resulted in the loss of the temperature-triggered morphological transition. The use of the reactive monomer PFBMA in PISA formulations presents a simple method to prepare well-defined nano-objects similar to those produced with non-reactive monomers (e.g. benzyl methacrylate) and to retain morphologies independent of solvent and temperature.

    E Ciampi, U Goerke, JL Keddie, PJ McDonald (2000)Lateral transport of water during drying of alkyd emulsions, In: LANGMUIR16(3)pp. 1057-1065 AMER CHEMICAL SOC
    DC Andrei, JL Keddie, JN Hay, SG Yeates, BJ Briscoe, D Parsonage (2001)Nano-mechanical properties and topography of thermosetting acrylic powder coatings, In: JOURNAL OF COATINGS TECHNOLOGY73(912)pp. 65-73 FEDERATION SOC COATING TECH
    P Worajittiphon, I Jurewicz, AA King, JL Keddie, AB Dalton (2010)Enhanced thermal actuation in thin polymer films through particle nano-squeezing by carbon nanotube belts., In: Adv Mater22(46)pp. 5310-5314
    R Sackin, E Ciampi, J Godward, JL Keddie, PJ McDonald (2001)Fickian ingress of binary solvent mixtures into glassy polymer, In: MACROMOLECULES34(4)pp. 890-895 AMER CHEMICAL SOC
    JL Keddie, P Meredith, RAL Jones, AM Donald (1998)Film formation of latices, In: MODERN ASPECTS OF COLLOIDAL DISPERSIONSpp. 51-59
    A Intaniwet, CA Mills, M Shkunov, H Thiem, JL Keddie, PJ Sellin (2009)Characterization of thick film poly(triarylamine) semiconductor diodes for direct x-ray detection, In: JOURNAL OF APPLIED PHYSICS106(6)ARTN 0pp. ?-? AMER INST PHYSICS
    A Utgenannt, Ross Maspero, Andrea Fortini, R Turner, Marian Florescu, Christopher Jeynes, AG Kanaras, OL Muskens, Richard Sear, Joseph Keddie (2016)Fast Assembly of Gold Nanoparticles in Large-Area 2-D Nanogrids Using a One-Step, Near-Infrared Radiation-Assisted Evaporation Process, In: ACS Nano10(2)pp. 2232-2242 American Chemical Society

    When fabricating photonic crystals from suspensions in volatile liquids using the horizontal deposition method, the conventional approach is to evaporate slowly to increase the time for particles to settle in an ordered, periodic close-packed structure. Here, we show that the greatest ordering of 10 nm aqueous gold nanoparticles (AuNPs) in a template of larger spherical polymer particles (mean diameter of 338 nm) is achieved with very fast water evaporation rates obtained with near-infrared radiative heating. Fabrication of arrays over areas of a few cm2 takes only seven minutes. The assembly process requires that the evaporation rate is fast relative to the particles’ Brownian diffusion. Then a two-dimensional colloidal crystal forms at the falling surface, which acts as a sieve through which the AuNPs pass, according to our Langevin dynamics computer simulations. With sufficiently fast evaporation rates, we create a hybrid structure consisting of a two-dimensional AuNP nanoarray (or “nanogrid”) on top of a three-dimensional polymer opal. The process is simple, fast and one-step. The interplay between the optical response of the plasmonic Au nanoarray and the microstructuring of the photonic opal results in unusual optical spectra with two extinction peaks, which are analyzed via finite-difference time-domain method simulations. Comparison between experimental and modelling results reveals a strong interplay of plasmonic modes and collective photonic effects, including the formation of a high-order stop band and slow-light enhanced plasmonic absorption. The structures, and hence their optical signatures, are tuned by adjusting the evaporation rate via the infrared power density.

    M Wallin, PM Glover, AC Hellgren, JL Keddie, PJ McDonald (2000)Depth profiles of polymer mobility during the film formation of a latex dispersion undergoing photoinitiated cross-linking, In: MACROMOLECULES33(22)pp. 8443-8452 AMER CHEMICAL SOC
    JL Keddie, JP Gorce, J Mallégol, PJ McDonald (2004)Understanding water-borne coatings: New techniques to answer old questions, In: Surface Coatings International Part A: Coatings Journal87(2)pp. 70-73
    T Wang, E Canetta, TG Weerakkody, JL Keddie (2009)pH Dependence of the Properties of Waterborne Pressure-Sensitive Adhesives Containing Acrylic Acid, In: ACS APPL MATER INTER1(3)pp. 631-639 AMER CHEMICAL SOC

    Polymer colloids are often copolymerized with acrylic acid monomers in order to impart colloidal stability. Here, the effects of the pH on the nanoscale and macroscopic adhesive properties of waterborne poly(butyl acrylate-co-acrylic acid) films are reported. In films cast from acidic colloidal dispersions, hydrogen bonding between carboxylic acid groups dominates the particle-particle interactions, whereas ionic dipolar interactions are dominant in films cast from basic dispersions. Force spectroscopy using an atomic force microscope and macroscale mechanical measurements show that latex films with hydrogen-bonding interactions have lower elastic moduli and are more deformable. They yield higher adhesion energies. On the other hand, in basic latex, ionic dipolar interactions increase the moduli of the dried films. These materials are stiffer and less deformable and, consequently, exhibit lower adhesion energies. The rate of water loss from acidic latex is slower, perhaps because of hydrogen bonding with the water. Therefore, although acid latex offers greater adhesion, there is a limitation in the film formation.

    G Malucelli, M Sangermano, R Bongiovanni, A Priola, JL Keddie (2000)Water sorption in polymer network films synthesised from PEO oligomers containing acrylic and vinyl ether functionalities, In: POLYMER BULLETIN45(4-5)pp. 431-438 SPRINGER
    J Mallegol, JL Keddie, O Dupont (2001)New insights into the imaging of waterborne acrylic pressure-sensitive adhesives by tapping mode AFM., In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY222pp. U346-U346 AMER CHEMICAL SOC
    T Wang, E Canetta, TG Weerakkody, JL Keddie (2009)pH Dependence of the Properties of Waterborne Pressure-Sensitive Adhesives Containing Acrylic Acid, In: ACS APPL MATER INTER1(3)pp. 631-639 AMER CHEMICAL SOC
    N Kessel, DR Illsley, JL Keddie (2008)The diacetone acrylamide crosslinking reaction and its influence on the film formation of an acrylic latex, In: JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH5(3)pp. 285-297 SPRINGER
    JL KEDDIE, RAL JONES (1995)Depression of the glass transition temperature in ultra-thin, grafted polystyrene films, In: DYNAMICS IN SMALL CONFINING SYSTEMS II366pp. 183-188 MATERIALS RESEARCH SOC
    T Wang, PJ Colver, SAF Bon, JL Keddie (2009)Soft polymer and nano-clay supracolloidal particles in adhesives: synergistic effects on mechanical properties, In: SOFT MATTER5(20)pp. 3842-3849 ROYAL SOC CHEMISTRY
    JL Keddie, P Meredith, RAL Jones, AM Donald (1996)Film formation of acrylic latices with varying concentrations of non-film-forming latex particles, In: LANGMUIR12(16)pp. 3793-3801 AMER CHEMICAL SOC
    E Canetta, J Marchal, C-H Lei, F Deplace, AM König, C Creton, K Ouzineb, JL Keddie (2009)A comparison of tackified, miniemulsion core-shell acrylic latex films with corresponding particle-blend films: Structure-property relationships, In: Langmuir25(18)pp. 11021-11031 American Chemical Society
    Laurie Little, Richard Sear, Joseph Keddie (2015)Does the gamma Polymorph of Glycine Nucleate Faster? A Quantitative Study of Nucleation from Aqueous Solution, In: Crystal Growth and Design15(11)pp. 5345-5354 American Chemical Society

    We advance the quantitative study of nucleation by combining the study of hundreds of samples, with statistical tests for reproducibility, and for well-defined nucleation rates. Unlike in most previous work, we find that in the samples that nucleate after the first hour of our experiment the equilibrium glycine polymorph predominates over the alpha form.

    A Georgiadis, PA Bryant, M Murray, P Beharrell, JL Keddie (2011)Resolving the Film-Formation Dilemma with Infrared Radiation-Assisted Sintering., In: Langmuir27(6)pp. 2176-2180 American Chemical Society

    The film formation of an acrylate latex with a glass-transition temperature of 38 °C has been achieved through the use of near-infrared (NIR) radiative heating. A hard, crack-free coating was obtained without the addition of plasticizers. Sintering of acrylate particles was confirmed through measurements using atomic force microscopy. The addition of an NIR-absorbing polymer increased the rate of particle deformation such that it was significantly greater than obtained in a convection oven at 60 °C. The results are consistent with a lower polymer viscosity under infrared radiation, according to a simple analysis using a standard model of sintering.

    Neutron reflection (NR), spectroscopic ellipsometry (SE), and atomic force microscopy (AFM) have been used to characterize the structure of self-assembled octadecyltrichlorosilane (OTS) layers on silicon. The first two of these techniques rely on modeling of the experimental data and may thus result in the unrealistic representation of the composition and structure at the interface. Ambiguities arise from model-dependent analysis complicated by the lack of sufficient external constraints to converge nonunique solutions to a unique one. We show in this work that AFM measurements provide extra constraints to allow us to obtain a physical description closer to the actual structure of the film. It was found that “the simpler the better” modeling strategy very often employed during the fitting of ellipsometric and neutron reflection data is, therefore, not necessarily the best way to obtain a reliable description of the interfacial structure. Our AFM findings necessitated the refit of both neutron and ellipsometric data that were previously described by a single-layer model. Interpretation of the structure of thin layers that is based only on indirect measurements such as SE, NR, and x-ray reflection techniques may be, therefore, misleading. A combined analysis of SE, NR, and AFM data suggests that the OTS film may comprise a rough layer, with pinholes down to bare silicon oxide surface, consisting at least of mono-, bi- and trilayers of OTS molecules.

    T Wang, AB Dalton, JL Keddie (2008)Importance of Molecular Friction in a Soft Polymer-Nanotube Nanocomposite, In: MACROMOLECULES41(20)pp. 7656-7661 AMER CHEMICAL SOC
    T Wang, C-H Lei, AB Dalton, M Manea, JM Asua, JL Keddie (2007)Waterborne nanocomposite pressure-sensitive adhesives: Achieving enhanced adhesion combined with electrical conductivity, In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY233 AMER CHEMICAL SOC
    JL Keddie, I Lopez-Garcia, H Richardson, M Sferrazza (2004)Thickness dependence of structural relaxation in spin-cast, glassy polymer thin films, In: Physical Review E70051805 American Physical Society

    The isothermal structural relaxation of glassy, spin-cast polymer thin films has been investigated. Specifically, the thickness, h, of freshly-cast poly(methyl methacrylate) thin films was measured over time using spectroscopic ellipsometry. The spin-cast films exhibit a gradual decrease in thickness, which is attributed to structural relaxation of the glass combined with simultaneous solvent loss. In all cases, h was found to be greater than the equilibrium thickness, h0, which is obtained by cooling slowly from the melt. It is observed that both the rate of the volume relaxation and the fractional departure from h0 (referred to as ∂o) increase with increasing film thickness. In the limit of very thin films, the initial h is close to h, and o is small, whereas in thick films (> 500 nm), a plateau value of ∂o of 0.16 is observed, which is close to the volume fraction of the solvent at the vitrification point. This dependence of ∂o on thickness is observed regardless of the substrate, polymer molecular weight, or angular velocity during spin-casting. Enhanced mobility near film surfaces could be leading to greater relaxation in thinner films prior to, and immediately after, the vitrification of the polymer during the deposition process.

    RS Gurney, D Dupin, E Siband, K Ouzineb, JL Keddie (2013)Large-area patterning of the tackiness of a nanocomposite adhesive by sintering of nanoparticles under IR radiation., In: ACS Appl Mater Interfaces5(6)pp. 2137-2145

    We present a simple technique to switch off the tack adhesion in selected areas of a colloidal nanocomposite adhesive. It is made from a blend of soft colloidal polymer particles and hard copolymer nanoparticles. In regions that are exposed to IR radiation, the nanoparticles sinter together to form a percolating skeleton, which hardens and stiffens the adhesive. The tack adhesion is lost locally. Masks can be made from silicone-coated disks, such as coins. Under the masks, adhesive island regions are defined with the surrounding regions being a nontacky coating. When optimizing the nanocomposite's adhesive properties, the addition of the hard nanoparticles raises the elastic modulus of the adhesive significantly, but adhesion is not lost because the yield point remains relatively low. During probe-tack testing, the soft polymer phases yield and enable fibrillation. After heating under IR radiation, the storage modulus increases by a factor of 5, and the yield point increases nearly by a factor of 6, such that yielding and fibrillation do not occur in the probe-tack testing. Hence, the adhesion is lost. Loading and unloading experiments indicate that a rigid skeleton is created when the nanoparticles sinter together, and it fractures under moderate strains. This patterning method is relatively simple and fast to execute. It is widely applicable to other blends of thermoplastic hard nanoparticles and larger soft particles.

    TRE Simpson, JL Keddie, B Parbhoo (2003)IR ellipsometry of crosslinking in silicone coatings: Effect of thickness, In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY225pp. U702-U702
    B Trottet, Marco Marconati, Joseph Keddie, Marco Ramaioli (2017)Mastering the Coating Thickness Obtained Using Liquids with a Yield-Stress, In: Chemical Engineering Transactions57pp. 1897-1902 The Italian Association of Chemical Engineering

    Dip coating is a very common process in food manufacturing. Controlling the thickness of the coating is key to deliver the desired sensorial properties and to be compliant with the product’s nutritional claims. Whilst dip coating with Newtonian liquids is physically well understood, coating food products almost invariably involve liquids with more complex rheology. This makes the process more difficult to design and control and reduces the coating homogeneity. Developing novel food products with improved nutritional attributes often calls for reducing the coating thickness and non-homogeneity should be avoided to guarantee the quality of the final product. In this study, we focused on the coating of a flat surface using Carbopol solutions and a commercial ketchup, following a Herschel-Bulkley rheological model. The final average coating thickness was always significantly lower than the critical thickness that can be estimated from liquid density and yield stress. Liquids with a yield stress in the range 4-56 Pa were considered in this study and the steady withdrawal speed from the bath was varied in the range 0.1-20 mm/s. The resulting average coating thickness and its uniformity are discussed. The results are interpreted in the context of an existing theory for dip coating with liquids with a yield stress. This study paves the way toward an integrated design of the coating process and the liquid rheology of foods, such as chocolate or ketchup. This can enable the development of new food products allying improved nutrition, a consumer preferred sensory profile and cost.

    JL Keddie, P Ekanayake, AM Koenig, TG Weerakkody, N Barber, D Johannsmann, RP Sear, PJ McDonald (2007)Influence of the colloidal stability of latex particles on their distribution in drying films, In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY234 AMER CHEMICAL SOC

    This book introduces the reader to latex, which is a colloidal dispersion of polymer particles in water, and explains how useful products are made from it.

    Yuxiu Chen, Simone Krings, Joshua R. Booth, Stefan A.F Bon, Suzie Hingley-Wilson, Joseph Keddie (2020)Introducing Porosity in Colloidal Biocoatings to Increase Bacterial Viability, In: Biomacromolecules American Chemical Society

    A biocoating confines non-growing, metabolically-active bacteria within a synthetic colloidal polymer (i.e. latex) film. Bacteria encapsulated inside biocoatings can perform useful functions, such as a biocatalyst in wastewater treatment. A biocoating needs to have high a permeability to allow a high rate of mass transfer for rehydration and the transport of both nutrients and metabolic products. It therefore requires an interconnected porous structure. Tuning the porosity architecture is a challenge. Here, we exploited rigid tubular nanoclays (halloysite) and non-toxic latex particles (with a relatively high glass transition temperature) as the colloidal “building blocks” to tailor the porosity inside biocoatings containing Escherichia coli bacteria as a model organism. Electron microscope images revealed inefficient packing of the rigid nanotubes and proved the existence of nanovoids along the halloysite/polymer interfaces. Single-cell observations using confocal laser scanning microscopy provided evidence for metabolic activity of the E. coli within the biocoatings through the expression of yellow fluorescent protein. A custom-built apparatus was used to measure the permeability of a fluorescein sodium salt in the biocoatings. Whereas there was no measurable permeability in a coating made from only latex particles, the permeability coefficient of the composite biocoatings increased with increasing halloysite content up to a value of 110-4 m h-1. The effects of this increase in permeability was demonstrated through a specially-developed resazurin reduction assay. Bacteria encapsulated in halloysite composite biocoatings had statistically significant higher metabolic activities in comparison to bacteria encapsulated in a non-optimized coating made from latex particles alone.

    I Jurewicz, JL Keddie, AB Dalton (2012)Importance of capillary forces in the assembly of carbon nanotubes in a polymer colloid lattice., In: Langmuir28(21)pp. 8266-8274 American Chemical Society

    We highlight the significance of capillary pressure in the directed assembly of nanorods in ordered arrays of colloidal particles. Specifically, we discuss mechanisms for the assembly of carbon nanotubes at the interstitial sites between latex polymer particles during composite film formation. Our study points to general design rules to be considered to optimize the ordering of nanostructures within such polymer matrices. In particular, gaining an understanding of the role of capillary forces is critical. Using a combination of electron microscopy and atomic force microscopy, we show that the capillary forces acting on the latex particles during the drying process are sufficient to bend carbon nanotubes. The extent of bending depends on the flexural rigidity of the carbon nanotubes and whether or not they are present as bundled ensembles. We also show that in order to achieve long-range ordering of the nanotubes templated by the polymer matrix, it is necessary for the polymer to be sufficiently mobile to ensure that the nanotubes are frozen into the ordered network when the film is formed and the capillary forces are no longer dominant. In our system, the polymer is plasticized by the addition of surfactant, so that it is sufficiently mobile at room temperature. Interestingly, the carbon nanotubes effectively act as localized pressure sensors, and as such, the study agrees well with previous theoretical predictions calculating the magnitude of capillary forces during latex film formation.

    BJ Lincoln, TRE Simpson, JL Keddie (2004)Water vapour sorption by the pedal mucus trail of a land snail, In: Colloids and Surfaces B: Biointerfaces33(3-4)pp. 251-258 Elsevier
    R Rodriguez, CDLH Alarcon, P Ekanayake, PJ McDonald, JL Keddie, MJ Barandiaran, JM Asua (2008)Correlation of Silicone Incorporation into Hybrid Acrylic Coatings with the Resulting Hydrophobic and Thermal Properties, In: MACROMOLECULES41(22)pp. 8537-8546 AMER CHEMICAL SOC
    BS Cooper, RS Gurney, Joseph Keddie, E Siband, D Dupin (2014)Power density threshold for switching off the tack adhesion of colloidal nanocomposites, In: Macromolecular Chemistry and Physics215(10)pp. 998-1003

    Colloidal nanocomposite adhesives are made by blending soft adhesive particles with hard nanoparticles (NPs) that sit at the particle boundaries to create a percolating phase. When the nanocomposite is heated with infrared (IR) radiation, the NPs sinter together to create a rigid structure that hardens the composite and thereby switches off the tack adhesion. It is discovered that the IR power density of an irradiation for 20 s must exceed a threshold value of 1.07 W cm before the tack is switched off. At lower power densities, an analysis of the sintering of the NPs shows that there is not sufficient time to link them together into a rigid structure. These results reveal that the switching of colloidal nanocomposite adhesives can be easily controlled through the IR power density and the time of the exposure. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

    GS Irmukhametova, BJ Fraser, JL Keddie, GA Mun, VV Khutoryanskiy (2012)Hydrogen-Bonding-Driven Self-Assembly of PEGylated Organosilica Nanoparticles with Poly(acrylic acid) in Aqueous Solutions and in Layer-by-Layer Deposition at Solid Surfaces, In: LANGMUIR28(1)pp. 299-306 American Chnemical Society

    PEGylated organosilica nanoparticles have been synthesized through self-condensation of 3-mercaptopropyltrimethoxysilane in dimethylsulfoxide into thiolated nanoparticles with their subsequent reaction with methoxypolyethylene glycol maleimide. The PEGylated nanoparticles showed excellent colloidal stability over a wide range of pHs in contrast to the parent thiolated nanoparticles, which have a tendency to aggregate irreversibly under acidic conditions (pH < 3.0). Due to the presence of a poly(ethylene glycol)-based corona, the PEGylated nanoparticles are capable of forming hydrogen-bonded interpolymer complexes with poly(acrylic acid) in aqueous solutions under acidic conditions, resulting in larger aggregates. The use of hydrogen-bonding interactions allows their more efficient attachment of the nanoparticles to surfaces. The alternating deposition of PEGylated nanoparticles and poly(acrylic acid) on silicon wafer surfaces in a layer-by-layer fashion leads to multilayered coatings. The self-assembly of PEGylated nanoparticles with poly(acrylic acid) in aqueous solutions and at solid surfaces was compared to the behavior of linear poly(ethylene glycol). The nanoparticle system creates thicker layers than the poly(ethylene glycol), and a thicker layer is obtained on a poly(acrylic acid) surface than on a silica surface, because of the effects of hydrogen bonding. Some implications of these hydrogen bonding-driven interactions between PEGylated nanoparticles and poly(acrylic acid) for pharmaceutical formulations are discussed.

    RS Gurney, D Dupin, JS Nunes, K Ouzineb, E Siband, JM Asua, SP Armes, JL Keddie (2012)Switching Off the Tackiness of a Nanocomposite Adhesive in 30 s via Infrared Sintering., In: ACS Appl Mater Interfaces4(10)pp. 5442-5452 American Chemical Society

    Soft adhesives require an optimum balance of viscous and elastic properties. Adhesion is poor when the material is either too solidlike or too liquidlike. The ability to switch tack adhesion off at a desired time has many applications, such as in recycling, disassembly of electronics, and painless removal of wound dressings. Here, we describe a new strategy to switch off the tack adhesion in a model nanocomposite adhesive in which temperature is the trigger. The nanocomposite comprises hard methacrylic nanoparticles blended with a colloidal dispersion of soft copolymer particles. At relatively low volume fractions, the nanoparticles (50 nm diameter) accumulate near the film surface, where they pack around the larger soft particles (270 nm). The viscoelasticity of the nanocomposite is adjusted via the nanoparticle concentration. When the nanocomposite is heated above the glass transition temperature of the nanoparticles (T(g) = 130 °C), they sinter together to create a rigid network that raises the elastic modulus at room temperature. The tackiness is switched off. Intense infrared radiation is used to heat the nanocomposites, leading to a fast temperature rise. Tack adhesion is switched off within 30 s in optimized compositions. These one-way switchable adhesives have the potential to be patterned through localized heating.

    Marcelo A. da Silva, Jie Kang, Tam T. T. Bui, Lisa M. Borges da Silva, Jake Burn, Joseph Keddie, Cecile Dreiss (2017)Tightening of Gelatin Chemically Cross-linked Networks Assisted by Physical Gelation, In: Journal of Polymer Science Part B: Polymer Physics55(24)pp. 1850-1858 Wiley

    Developing the use of polymers from renewable sources to build hydrogels with tailored mechanical properties has become an increasing focus of research. The impact of the thermo-reversible physical networks of gelatin (arising from the formation of triple-helices) on the structure formation of a chemical network, obtained by cross-linking with glutaraldehyde (a non-catalytic cross-linker), was studied using optical rotation, oscillatory rheology and large strain mechanical deformation. We observed a direct correlation between the storage shear modulus of the chemical network grown in the gel state (i.e. simultaneously with the physical network) and the amount of gelatin residues in the triple-helix conformation (χ). Since χ is directly affected by temperature, the value of the storage modulus is also sensitive to changes in the temperature of gel formation. χ values as low as 12% lead to an increase of the shear storage modulus of the cross-linked gel by a factor of 2.7, when compared to a chemical network obtained in the sol state (i.e. in the absence of a physical network). Our results show that the physical network acts as a template, which leads to a greater density of the chemical cross-links and a corresponding higher elastic modulus, beyond what is otherwise achieved in the absence of a physical network.

    Prodromos Chatzispyroglou, Joseph L. Keddie, Paul J. Sellin (2020)Boron-loaded Polymeric Sensor for the Direct Detection of Thermal Neutrons, In: ACS Applied Materials & Interfaces12(29)pp. 33050-33057 American Chemical Society

    We report the first demonstration of a solid-state, direct-conversion sensor for thermal neutrons based on a polymer/inorganic nanocomposite. Sensors were fabricated from ultra-thick films of poly(triarylamine) (PTAA) semiconducting polymer, with thicknesses up to 100 μm. Boron nanoparticles were dispersed throughout the PTAA film to provide the neutron stopping power arising from the high thermal neutron cross-section of the isotope Boron-10. To maximize the quantum efficiency of the sensor to thermal neutrons, a high volume fraction of homogeneously dispersed boron nanoparticles was achieved in the thick PTAA film using an optimized processing method. Thick active layers were realized using a high molecular weight of the PTAA so that molecular entanglements provide a high cohesive strength. A non-ionic surfactant was used to stabilize the boron dispersion in solvent and hence suppress the formation of agglomerates and associated electrical pathways. Boron nanoparticle loadings of up to ten volume percent were achieved, with thermal neutron quantum efficiency estimates up to 6% resulting. The sensors' neutron responses were characterized under a high flux thermal neutron exposure, showing a linear correlation between the response current and the thermal neutron flux. Polymer-based boron nanocomposite sensors offer a new neutron detection technology that uses low-cost, scalable solution processing, and provides an alternative to traditional neutron sensors that use rare isotopes, such as Helium-3.

    VR Gundabala, C-H Lei, K Ouzineb, O Dupont, JL Keddie, AF Routh (2008)Lateral surface nonuniformities in drying latex films, In: AIChE Journal54(12)pp. 3092-3105 Wiley

    The length scales of film, thickness nonuniformities, commonly observed in polymer colloid (i.e., latex) films, are predicted. This prediction is achieved by investigating the stability behavior of drying latex films. A linear stability analysis is performed on a base solution representing a uniformly drying latex film containing a surfactant. The analysis identifies film thickness nonuniformities over two length scales: long (millimeter) range (from lubrication theory) and short (micrometer) range (from nonlubrication theory). Evaporation and surfactant desorption into the bulk film are identified as the primary destabilizing mechanisms during drying. Experimental evidence through direct visualization and atomic force microscopy confirm the existence of nonuniformities over both length scales, which are shown to be functions of parameters such as initial particle volume fraction, surfactant amount, and desorption strength, while being independent of drying rate. © 2008 American Institute of Chemical Engineers.

    Ignacio Martín-Fabiani, Jennifer Lesage de la Haye, Malin Schulz, Yang Liu, Michelle Lee, Brendan Duffy, Franck D’Agosto, Muriel Lansalot, Joseph Keddie (2018)Enhanced Water Barrier Properties of Surfactant-Free Polymer Films Obtained by MacroRAFT-Mediated Emulsion Polymerization, In: ACS Applied Materials and Interfaces10(13)pp. 11221-11232 American Chemical Society

    The presence of low molar mass surfactants in latex films results in detrimental effects on their water permeability, gloss and adhesion. For applications as coatings, there is a need to develop formulations that do not contain surfactants and that have better water barrier properties. Having previously reported the synthesis of surfactant-free latex particles in water using low amounts (< 2 wt%) of controlled radical polymer chains (Lesage de la Haye et al. Macromolecules 2017, 50, 9315−9328), here we study the water barrier properties of films made from these particles and their application in anti-corrosion coatings. When films cast from aqueous dispersions of acrylate copolymer particles stabilized with poly(sodium 4-styrenesulfonate) (PSSNa) were immersed in water for three days, they sorbed only 4 wt.% water. This uptake is only slightly higher than the value predicted for the pure copolymer, indicating that the negative effects of any particle boundaries and hydrophilic stabilizing molecules are minimal. This sorption of liquid water is five times lower than what is found in films cast from particles stabilized with the same proportion of poly(methacrylic acid) (PMAA), which is more hydrophilic than PSSNa. In water vapor with 90% relative humidity, the PSSNa-based film had an equilibrium sorption of only 4 wt.%. A small increase in the PMAA content has a strong and negative impact on the barrier properties. Nuclear magnetic resonance relaxometry on polymer films after immersion in water shows that water clusters have the smallest size in the films containing PSSNa. Furthermore, these films retain their optical clarity during immersion in liquid water for up to 90 minutes, whereas all other compositions quickly develop opacity (“water whitening”) as a result of light scattering from sorbed water. This implies a remarkably complete coalescence and a very small density of defects, which yields properties matching those of some solvent borne films. The latex stabilized with PSSNa is implemented as the binder in a paint formulation for application as an anti-corrosive barrier coating on steel substrates and evaluated in accelerated weathering and corrosion tests. Our results demonstrate the potential of self-stabilized latex particles for the development of different applications, such as waterborne protective coatings and pressure-sensitive adhesives.

    P Vandervorst, C-H Lei, Y Lin, O Dupont, AB Dalton, Y-P Sun, JL Keddie (2006)The fine dispersion of functionalized carbon nanotubes in acrylic latex coatings, In: Progress in Organic Coatings57(2)pp. 91-97 Elsevier

    Nanocomposites of a polymer and carbon nanotubes exhibit high electrical and thermal conductivity and enhanced mechanical properties in comparison to the polymer alone. Film formation from latex dispersions is an ideal way to create nanocomposite coatings with the advantages of solvent-free processing and a high uniformity of dispersion. It is shown here that carbon nanotubes functionalised with poly(vinyl alcohol) (PVA) can be blended with two types of acrylic latex to create stable colloidal dispersions without the need for added surfactant or emulsifier. Waterborne nanocomposite films with optical transparency can be formed. Microscopic analysis shows that the PVA-functionalized nanotubes are finely and uniformly dispersed in the polymer matrix.

    J Keddie, J Mallegol, O Dupont (2001)The technological and environmental pressures on advanced adhesives, In: MATERIALS WORLD9(11)pp. 22-24 I O M COMMUNICATIONS LTD INST MATERIALS
    H Richardson, I Lopez-Garcia, M Sferrazza, J L Keddie (2004)Thickness Dependence of Structural Relaxation in Spin-Cast, Glassy Polymer Thin Films, In: Physical Review E70(5)

    The isothermal structural relaxation of glassy, spin-cast polymer thin films has been investigated. Specifically, the thickness h of freshly cast poly(methyl methacrylate) thin films was measured over time using spectroscopic ellipsometry. The spin-cast films exhibit a gradual decrease in thickness, which is attributed to structural relaxation of the glass combined with simultaneous solvent loss. In all cases, It was found to be greater than the equilibrium thickness h(infinity), which is obtained by cooling slowly from the melt. It is observed that both the rate of the volume relaxation and the fractional departure from h. (referred to as delta(0)) increase with increasing film thickness. In the limit of very thin films, the initial h is close to h(infinity), and delta(0) is small, whereas in thick films (>500 nm), a plateau value of delta(0) of 0.16 is observed, which is close to the volume fraction of the solvent at the vitrification point. This dependence of) on thickness is observed regardless of the substrate, polymer molecular weight, or angular velocity during spin casting. Enhanced mobility near film surfaces could be leading to greater relaxation in thinner films prior to, and immediately after, the vitrification of the polymer during the deposition process.

    RE Trueman, E Lago Domingues, SN Emmett, MW Murray, JL Keddie, AF Routh (2012)Autostratification in drying colloidal dispersions: experimental investigations, In: Langmuir28(7)pp. 3420-3428 American Chemical Society

    In films cast from a colloidal dispersion comprising two particle sizes, we experimentally examine the distribution of particles normal to the substrate. The particle concentrations at various positions in the film are determined through atomic force microscopy and NMR profiling. The results are compared to a previously derived diffusional model. Evidence for diffusional driven stratification is found, but the importance of other flows is also highlighted. The conditions that enhance particle stratification are found to be a colloidally stable dispersion, low initial volume fractions, a low concentration of the stratifying particle, and for the Peclet numbers of the two components to straddle unity.

    JL Keddie, T Wang, I Jurewicz, AB Dalton, C Creton, M Manea, JM Asua (2007)Multifunctional nanocomposites of soft polymer colloids and carbon nanotubes, In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY234 AMER CHEMICAL SOC
    E Daar, W Kaabar, C Lei, JL Keddie, A Nisbet, DA Bradley (2010)AFM and uni-axial testing of pericardium exposed to radiotherapy doses, In: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment652(1)pp. 874-877 Elsevier
    David Makepeace, Andrea Fortini, A Markov, P Locatelli, C Lindsay, S Moorhouse, R Lind, Richard Sear, Joseph Keddie (2017)Stratification in Binary Colloidal Polymer Films: Experiment and Simulations, In: Soft Matter13pp. 6969-6980 Royal Society of Chemistry

    When films are deposited from mixtures of colloidal particles of two different sizes, a diverse range of functional structures can result. One structure of particular interest is a stratified film in which the top surface layer has a composition different than in the interior. Here, we explore the conditions under which a stratified layer of small particles develops spontaneously in a colloidal film that is cast from a binary mixture of small and large polymer particles that are suspended in water. A recent model, which considers the cross-interaction between the large and small particles (Zhou et al., Phys. Rev. Lett. (2017) 118, 108002), predicts that stratification will develop from dilute binary mixtures when the particle size ratio (), initial volume fraction of small particles ( s), and Péclet number are high. In experiments and Langevin dynamics simulations, we systematically vary and s in both dilute and concentrated suspensions. We find that stratified films develop when  s is increased, which is in agreement with the model. In dilute suspensions, there is reasonable agreement between the experiments and the Zhou et al. model. In concentrated suspensions, stratification occurs in experiments only for the higher size ratio  = 7. Simulations using a high Péclet number, additionally find stratification with  = 2, when  s is high enough. Our results provide a quantitative understanding of the conditions under which stratified colloidal films assemble. Our research has relevance for the design of coatings with targeted optical and mechanical properties at their surface.

    I Martin-Fabiani, Andrea Fortini, J Lesage de la Haye, ML Koh, Spencer Taylor, E Bourgeat-Lami, M Lansalot, F D’Agosto, Richard Sear, Joseph Keddie (2016)pH-Switchable Stratification of Colloidal Coatings: Surfaces “On Demand”, In: ACS Applied Materials and Interfaces8(50)pp. 34755-34761 American Chemical Society

    Stratified coatings are used to provide properties at a surface, such as hardness or refractive index, which are different from underlying layers. Although time-savings are offered by self-assembly approaches, there have been no methods yet reported to offer stratification on demand. Here, we demonstrate a strategy to create self-assembled stratified coatings, which can be switched to homogenous structures when required. We use blends of large and small colloidal polymer particle dispersions in water that self-assemble during drying because of an osmotic pressure gradient that leads to a downward velocity of larger particles. Our confocal fluorescent microscopy images reveal a distinct surface layer created by the small particles. When the pH of the initial dispersion is raised, the hydrophilic shells of the small particles swell substantially, and the stratification is switched off. Brownian dynamics simulations explain the suppression of stratifi-cation when the small particles are swollen as a result of reduced particle mobility, a drop in the pressure gradient, and less time available before particle jamming. Our strategy paves the way for applications in antireflection films and pro-tective coatings in which the required surface composition can be achieved on demand, simply by adjusting the pH prior to deposition.

    V Daniloska, JL Keddie, JM Asua, R Tomovska (2014)MoS2 Nanoplatelet Fillers for Enhancement of the Properties of Waterborne Pressure-Sensitive Adhesives, In: ACS APPLIED MATERIALS & INTERFACES6(24)pp. 22640-22648 AMER CHEMICAL SOC
    A Intaniwet, JL Keddie, M Shkunov, PJ Sellin (2011)High charge-carrier mobilities in blends of poly(triarylamine) and TIPS-pentacene leading to better performing X-ray sensors, In: Organic Electronics12(11)pp. 1903-1908 Elsevier

    A new class of X-ray sensor – in which there is a blend of poly(triarylamine) (PTAA) and 6,13-bis(triisopropylsilylethynyl) (TIPS)-pentacene in the active layer of a diode structure – has been developed. The crystalline pentacene provides a fast route for charge carriers and leads to enhanced performance of the sensor. The first time-of-flight charge-carrier mobility measurement of this blend is reported. The mobility of PTAA and TIPS-pentacene in a 1:25 molar ratio was found to be 2.2 × 10−5 cm2 V−1 s−1 (averaged for field strengths between 3 × 104 and 4 × 105 V cm−1), which is about 17 times higher than that obtained in PTAA over the same range of field strengths. This higher mobility is correlated with a fourfold increase in the X-ray detection sensitivity in the PTAA:TIPS-pentacene devices.

    A Tzitzinou, JL Keddie, C Jeynes, M Mulder, J Geurts, KE Treacher, R Satguru, P Zhdan (1999)Molecular weight effects on film formation of latex and surfactant morphology., In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY218pp. U609-U609 AMER CHEMICAL SOC
    D Liu, T Wang, JL Keddie (2009)Protein Nanopatterning on Self-Organized Poly(styrene-b-isoprene) Thin Film Templates, In: LANGMUIR25(8)pp. 4526-4534 American Chemical Society

    Templated surfaces can be used to create patterns of proteins for applications in cell biology, biosensors, and tissue engineering. A diblock copolymer template, which contains a pair of hydrophobic blocks, has been developed. The template is created from well-ordered, nonequilibrium surface structures of poly(styrene-b-isoprene) (PS-b-PI) diblock copolymers, which are achieved in ultrathin films having a thickness of less than one domain period. Adsorption and nanopatterning of bovine serum albumin (BSA) on these thin films were studied. After incubation of the copolymer templates in BSA solutions (500 μg/mL) for a period of 1 h, BSA molecules formed either a striped or a dense, ringlike structure, closely resembling the underlying polymer templates. In this “hard-soft” PS-b-PI system, BSA molecules were preferentially adsorbed on the hard PS domains, rather than on the soft PI domains. Secondary ion mass spectroscopy (SIMS) and contact angle analysis revealed that, with more PI localized at the free surface, fewer BSA molecules were adsorbed. SIMS analysis confirmed that BSA molecules were adsorbed selectively on the PS blocks. This is the first example of two hydrophobic blocks of a diblock copolymer being used as a protein patterning template. Previously reported diblock copolymer templates used hydrophilic and hydrophobic pairs. A potentially useful characteristic of this template is that it is effective at high protein solution concentrations (up to 1 mg/mL) and for long incubation times (up to 2 h), which broadens its range of applicability in various uses.

    E Aramendia, J Mallegol, C Jeynes, MJ Barandiaran, JL Keddie, JM Asua (2003)Distribution of surfactants near acrylic latex film surfaces: A comparison of conventional and reactive surfactants (surfmers), In: LANGMUIR19(8)pp. 3212-3221 AMER CHEMICAL SOC
    V Nerapusri, JL Keddie, B Vincent, IA Bushnak (2006)Swelling and deswelling of adsorbed microgel monolayers triggered by changes in temperature, pH, and electrolyte concentration, In: LANGMUIR22(11)pp. 5036-5041 AMER CHEMICAL SOC
    IA Bushnak, FH Labeed, RP Sear, JL Keddie (2010)Adhesion of microorganisms to bovine submaxillary mucin coatings: effect of coating deposition conditions, In: BIOFOULING26(4)pp. 387-397 TAYLOR & FRANCIS LTD

    The adhesion of Staphylococcus epidermidis, Escherichia coli, and Candida albicans on mucin coatings was evaluated to explore the feasibility of using the coating to increase the infection resistance of biomaterials. Coatings of bovine submaxillary mucin (BSM) were deposited on a base layer consisting of a poly(acrylic acid-b-methyl methacrylate) (PAA-b-PMMA) diblock copolymer. This bi-layer system exploits the mucoadhesive interactions of the PAA block to aid the adhesion of mucin to the substratum, whereas the PMMA block prevents dissolution of the coating in aqueous environments. The thickness of the mucin coating was adjusted by varying the pH of the solution from which it was deposited. Thin mucin coatings decreased the numbers of bacteria but increased the numbers of C. albicans adhering to the copolymer and control surfaces. Increasing the mucin film thickness resulted in a further lowering of the density of adhering S. epidermidis cells, but it did not affect the density of E. coli. In contrast, the density of C. albicans increased with an increase in mucin thickness.

    M Bradley, D Liu, JL Keddie, B Vincent, G Burnett (2009)The Uptake and Release of Cationic Surfactant from polyampholyte Microgel Particles in Dispersion and as an Adsorbed Monolayer, In: LANGMUIR25(17)pp. 9677-9683 AMER CHEMICAL SOC
    JL Keddie (2009)Mapping the route from wet to dry, In: European Coatings Journal(11)pp. 28-32
    D Liu, CAC Abdullah, RP Sear, JL Keddie (2010)Cell adhesion on nanopatterned fibronectin substrates, In: SOFT MATTER6(21)pp. 5408-5416 ROYAL SOC CHEMISTRY

    The coating of substrates with an extracellular matrix (ECM) protein, such as fibronectin (FN), is often employed to increase cell adhesion and growth. Here, we examine the influence of the size scale and geometry of novel FN nanopatterns on the adhesion and spreading of Chinese Hamster Ovary (CHO) cells. The FN is patterned on the surface of templates created through the self-assembly of polystyrene-block-polyisoprene (PS-b-PI) diblock copolymers. Both ring-like and stripe-like FN nanopatterns are created through the preferential adsorption of FN on PS blocks, as confirmed through the complementary use of atomic force microscopy and secondary ion mass spectrometry. The ring-like FN nanopattern substrate increases the cells' adhesion compared with the cells on homogeneous FN surfaces and the stripe-like FN nanopatterns. Cell adhesion is high when the FN ring size is greater than 50 nm and when the surface coverage of FN is less than ca. 85%. We suggest that the ring-like nanopatterns of FN may be aiding cell adhesion by increasing the clustering of the proteins (integrins) with which cells bind to the nanopatterned substrate. This clustering is required for cell adhesion. In comparison to lithographic techniques, the FN templating method, presented here, provides a simple, convenient and economical way of coating substrates for tissue cultures and should be applicable to tissue engineering.

    Ignacio Martín-Fabiani, Ming Liang Koh, Florent Dalmas, Katrin Elidottir, Steven J. Hinder, Izabela Jurewicz, Muriel Lansalot, Elodie Bourgeat-Lami, Joseph L. Keddie (2018)Design of Waterborne Nanoceria/Polymer Nanocomposite UV-Absorbing Coatings: Pickering versus Blended Particles, In: ACS Applied Nano Materials1(8)pp. 3956-3968 American Chemical Society

    Nanoparticles of cerium dioxide (or nanoceria) are of interest because of their oxygen buffering, photocatalytic ability, and high UV absorption. For applications, the nanoceria can be incorporated in a polymer binder, but questions remain about the link between the nanoparticle distribution and the resulting nanocomposite properties. Here, the thermal, mechanical and optical properties of polymer/ceria nanocomposites are correlated with their nanostructures. Specifically, nanocomposites made from waterborne Pickering particles with nanoceria shells are compared to nanocomposites made from blending the equivalent surfactant-free copolymer particles with nanoceria. Two types of nanoceria (protonated or citric acid-coated) are compared in the Pickering particles. A higher surface coverage is obtained with the protonated ceria, which results in a distinct cellular structure with nanoceria walls within the nanocomposite. In the blend of particles, a strong attraction between the protonated nanoceria and the acrylic acid groups of the copolymer likewise leads to a cellular structure. This structure offers transparency in the visible region combined with strong UV absorption, which is desired for UV blocking coating applications. Not having an attraction to the polymer, the citric acid-coated nanoceria forms agglomerates that lead to undesirable light scattering in the nanocomposite and yellowing. This latter type of nanocomposite coating is less effective in protecting substrates from UV damage but provides a better barrier to water. This work shows how the nanoparticle chemical functionalization can be used to manipulate the structure and to tailor the properties of UV-absorbing barrier coatings.

    T Wang, D Liu, JL Keddie (2007)An alternative approach to the modification of talc for the fabrication of polypropylene/Talc composites, In: JOURNAL OF APPLIED POLYMER SCIENCE106(1)pp. 386-393 JOHN WILEY & SONS INC
    C-H Lei, K Ouzineb, O Dupont, AF Routh, VR Gundabala, SJ Hinder, JL Keddie (2007)Lateral distribution of surfactants in waterborne pressure sensitive adhesive films: Theory and experiment, In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY233pp. ?-? AMER CHEMICAL SOC
    Nicolas Busatto, Joseph Keddie, Peter J. Roth (2019)Sphere-to-worm morphological transitions and size changes through thiol–para-fluoro core modification of PISA-made nano-objects, In: Polymer Chemistry Royal Society of Chemistry

    Postpolymerization modification is a powerful strategy to change the chemical functionality of pre-made polymers, but only limited approaches exist to modify functionality as well as the shape and behaviour of nano-particles. Herein, poly[poly(ethylene glycol) methyl ether methacrylate]-poly(2,3,4,5,6-pentafluorobenzyl methacrylate) nano-objects (pPEGMA-pPFBMA) prepared via RAFT dispersion polymerization with concurrent polymerization-induced self-assembly (PISA) in ethanol with either spherical or worm-shaped morphology were modified, post-synthesis, with a selection of 15 different thiols through thiol–para-fluoro substitution reactions in the nano-object cores. Depending on the choice of thiol, spherical nano-objects underwent an order–disorder transition to form unimers, increased in size, or underwent an order–order transition to form worm-shaped nano-objects. The core solvophobicity was found to be more important in driving a morphological transition than the modification efficiency, mass increase of the core block, or the glass transition temperature of the (partially) modified cores. These findings are relevant to the development of a “universal nanoparticle precursor” approach that allows the tuning of functionality, behaviour, size, and shape of a pre-made nano-object sample on demand.

    A Agirre, C de las Heras-Alarcon, T Wang, JL Keddie, JM Asua (2010)Waterborne, Semicrystalline, Pressure-Sensitive Adhesives with Temperature-Responsiveness and Optimum Properties, In: ACS APPLIED MATERIALS & INTERFACES2(2)pp. 443-451 AMER CHEMICAL SOC
    C Jeynes, M Florescu, A Fortini, RP Sear, JL Keddie (2016)Data for Utgenannt et al - ACS Nano University of Surrey
    Jennifer Lesage de la Haye, Ignacio Martin-Fabiani, Malin Schulz, Joseph Keddie, Franck D’Agosto, Muriel Lansalot (2017)Hydrophilic MacroRAFT-Mediated Emulsion Polymerization: Synthesis of Latexes for Cross-linked and Surfactant-Free Films, In: Macromolecules50(23)pp. 9315-9328 American Chemical Society

    A major drawback of conventional emulsion polymers arises from the presence of migrating low molecular weight surfactants that contribute to poor water barrier properties and low adhesion to substrates. In this paper, we demonstrate how living polymer chains obtained by reversible addition-fragmentation chain transfer (RAFT) can be used as an efficient stabilizer in emulsion polymerization, leading to the production of surfactant-free latexes, which then form crosslinked films with beneficial properties. Hydrophilic poly(methacrylic acid) (PMAA) chains obtained by RAFT performed in water are used to mediate emulsion polymerization and produce film-forming latex particles from mixtures of methyl 2 methacrylate, n-butyl acrylate and styrene. Stable dispersions of particles with sizes between 100 and 200 nm are obtained, with very low amounts of coagulum (< 0.5 wt.%). The particles are stabilized by the PMAA segment of amphiphilic block copolymers formed during the polymerization. Remarkably, low amounts of PMAA chains (from 1.5 wt.% down to 0.75 wt.%) are enough to ensure particle stabilization. Only traces of residual PMAA macroRAFT agents are detected in the final latexes, showing that most of them are successfully chain extended and anchored on the particle surface. The Tg of the final material is adjusted by the composition of the hydrophobic monomer mixture so that film formation occurs at room temperature. Conventional crosslinking strategies using additional hydrophobic co-monomers, such as 1,3-butanediol diacrylate (BuDA), diacetone acrylamide (DAAm), and (2-acetoacetoxy)ethyl methacrylate, are successfully applied to these formulations as attested by gel fractions of 100%. When particles are internally crosslinked with BuDA, chain interdiffusion between particles is restricted, and a weak and brittle film is formed. In contrast, when DAAm undergoes crosslinking during film formation, full coalescence is achieved along with the creation of a crosslinked network. The resulting film has a higher Young’s modulus and tensile strength as a result of crosslinking. This synthetic strategy advantageously yields a surfactant-free latex that can be formed into a film at room temperature with mechanical properties that can be tuned via the crosslinking density.

    JL Keddie, DC Andrei, RPL Sear, SG Yeates (1999)Surface flattening of thermosetting powder coatings: Theory and experiment., In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY218pp. U626-U626 AMER CHEMICAL SOC
    T Wang, JL Keddie (2009)Design and fabrication of colloidal polymer nanocomposites, In: Advances in Colloid and Interface Science147-14pp. 319-332 ELSEVIER SCIENCE BV

    It is well established that colloidal polymer particles can be used to create organised structures by methods of horizontal deposition, vertical deposition, spin-casting, and surface pattern-assisted deposition. Each particle acts as a building block in the structure. This paper reviews how two-phase (or hybrid) polymer colloids can offer an attractive method to create nanocomposites. Structure in the composite can be controlled at the nanoscale by using such particles. Methods to create armored particles, such as via methods of hetero-flocculation and Pickering polymerization, are of particular interest here. Polymer colloids can also be blended with other types of nanoparticles, e.g. nanotubes and clay platelets, to create nanocomposites. Structure can be controlled over length scales approaching the macroscopic through the assembly of hybrid particles or particle blends via any of the various deposition methods. Colloidal nanocomposites can offer unprecedented long-range 2D or 3D order that provides a periodic modulation of physical properties. They can also be employed as porous templates for further nanomaterial fabrication. Challenges in the design and control of the macroscopic properties, especially mechanical, are considered. The importance of the internal interfacial structure (e.g. between inorganic and polymer particles) is highlighted.

    A Intaniwet, CA Mills, PJ Sellin, M Shkunov, JL Keddie (2010)Achieving a Stable Time Response in Polymeric Radiation Sensors under Charge Injection by X-rays, In: ACS APPL MATER INTER2(6)pp. 1692-1699 AMER CHEMICAL SOC

    Existing inorganic materials for radiation sensors suffer from several drawbacks, including their inability to cover large curved areas, lack of tissue equivalence toxicity, and mechanical inflexibility. As an alternative to inorganics, poly(triarylamine) (PTAA) diodes have been evaluated for their suitability for detecting radiation via the direct creation of X-ray induced photocurrents. A single layer of PTAA is deposited on indium tin oxide (ITO) substrates, with top electrodes selected from Al, Au, Ni, and Pd. The choice of metal electrode has a pronounced effect on the performance of the device; there is a direct correlation between the diode rectification factor and the metal-PTAA barrier height. A diode with an Al contact shows the highest quality of rectifying junction, and it produces a high X-ray photocurrent (several nA) that is stable during continuous exposure to 50 kV Mo K alpha X-radiation over long time scales, combined with a high signal-to-noise ratio with fast response times of less than 0.25 s. Diodes with a low band gap, 'Ohmic' contact, such as ITO/PTAA/Au, show a slow transient response. This result can be explained by the build-up of space charge at the metal-PTAA interface, caused by a high level of charge injection due to X-ray-induced carriers. These data provide new insights into the optimum selection of metals for Schottky contacts on organic materials, with wider applications in light sensors and photovoltaic devices.

    CH Lei, K Ouzineb, O Dupont, JL Keddie (2007)Probing particle structure in waterborne pressure-sensitive adhesives with atomic force microscopy, In: JOURNAL OF COLLOID AND INTERFACE SCIENCE307(1)pp. 56-63 ACADEMIC PRESS INC ELSEVIER SCIENCE
    M Schulz, C Crean, R Brinkhuis, R.P Sear, J.L Keddie (2021)Determination of parameters for self-stratification in bimodal colloidal coatings using Raman depth profiling, In: Progress in Organic Coatings157106272 Elsevier B.V

    In waterborne mixtures of colloidal particles with differing sizes, the spontaneous stratification of one species of particle in a coating – driven by diffusiophoresis - offers the possibility to tailor the surface properties. However, despite strong research interest in stratification in recent years, the acceptable range of experimental parameters has not been fully explored, and the extent of stratification that is achievable has not yet been quantified. Here, we study the stratification of bimodal mixtures of waterborne polyurethane particles mixed with larger acrylic particles. We use ultra-low angle microtoming to prepare cross-sections of coating samples and analyse compositions quantitatively with Raman mapping. We use this method to obtain high-resolution depth profiles of the polyurethane phase in the coating with spacing between measurements corresponding to a few tens of nm. We experimentally test a model of diffusiophoresis and observe stratification when the processing parameters (evaporation rates, film thickness, and volume fraction of small particles) fall within the required range. Samples that exhibit stratification have top layer thicknesses on the order of tens of μm, which is a significant depth for exploitation in coatings aiming to modify surface properties. To guide the design of coatings in applications, we draw on the model to define the range of parameters in which self-stratification is expected. Our results provide a fundamental understanding that will enable the fabrication of tailored coatings in which the properties of the surface differ from the bulk material.

    V Nerapusri, JL Keddie, B Vincent, LA Bushnak (2007)Absorption of cetylpyridinium chloride into Poly(N-isopropylacrylamide)-Based microgel particles, in dispersion and as surface-deposited monolayers, In: LANGMUIR23(19)pp. 9572-9577 AMER CHEMICAL SOC

    The addition of cetylpyridinium chloride (CPC) to aqueous dispersions of poly(N-isopropylacrylamide) [poly(NIPAM)] and poly(N-isopropylacrylamide-co-acrylic acid) [poly(NIPAM-co-AAc)] microgel particles leads to absorption of the CPC into the particles and to corresponding changes in their hydrodynamic diameter. With the latter set of particles there is a strong pH dependence. The dependence of both hydrodynamic diameter and electrophoretic mobility of the microgel particles on the added CPC concentration show a strong correlation with CPC uptake, as obtained from direct CPC absorption measurements. Various mechanisms for CPC absorption into the microgel particles are postulated, including electrostatic, polar, and hydrophobic interactions. A comparison has also been made between the effect of added CPC on the hydrodynamic diameter of free microgel particles in dispersion, determined by dynamic light scattering, and the thickness of adsorbed monolayers of the same microgel particles deposited on cationically modified, oxidized silicon surfaces, as determined from ellipsometry measurements. The trends observed in both cases are broadly similar. This work opens the way for development of microgel layers for controlled uptake and release applications.

    Laurie Little, Alice A. K. King, Richard Sear, Joseph Keddie (2017)Controlling the crystal polymorph by exploiting the time dependence of nucleation rates, In: Journal of Chemical Physics147(14) AIP Publishing

    Most substances can crystallise into two or more different crystal lattices, called polymorphs. Despite this, there are no systems in which we can quantitatively predict the probability of one competing polymorph forming, instead of the other. We address this problem using large scale (hundreds of events) studies of the competing nucleation of the alpha and gamma polymorphs of glycine. In situ Raman spectroscopy is used to identify the polymorph of each crystal. We find that the nucleation kinetics of the two polymorphs is very different. Nucleation of the alpha polymorph starts off slowly but accelerates, while nucleation of the gamma polymorph starts off fast but then slows. We exploit this difference to increase the purity with which we obtain the gamma polymorph by a factor of ten. The statistics of the nucleation of crystals is analogous to that human mortality, and using a result from medical statistics we show that conventional nucleation data can say nothing about what, if any, are the correlations between competing nucleation processes. Thus we can show that it is impossible to disentangle the competing nucleation processes. We also find that the growth rate and the shape of a crystal depends on when it nucleated. This is new evidence that nucleation and growth are linked.

    A Georgiadis, AF Routh, MW Murray, JL Keddie (2011)Bespoke periodic topography in hard polymer films by infrared radiation-assisted evaporative lithography, In: Soft Matter7(23)pp. 11098-11102 ROYAL SOCIETY OF CHEMISTRY
    Ignacio Martín-Fabiani, David K. Makepeace, Philip G. Richardson, Jennifer Lesage de la Haye, Diego Alba Venero, Sarah E. Rogers, Franck D’Agosto, Muriel Lansalot, Joseph L. Keddie (2019)In Situ Monitoring of Latex Film Formation by Small-Angle Neutron Scattering: Evolving Distributions of Hydrophilic Stabilizers in Drying Colloidal Films, In: Langmuir35(10)pp. pp 3822-3831 American Chemical Society

    The distribution of hydrophilic species, such as surfactants, in latex films is of critical importance for the performance of adhesives, coatings, and inks, among others. However, the evolution of this distribution during the film formation process and in the resulting dried films remains insufficiently elucidated. Here, we present in situ (wet) and ex situ (dry) small-angle neutron scattering (SANS) experiments that follow the film formation of two types of latex particles, which differ in their stabilizer: either a covalently bonded poly(methacrylic acid) (PMAA) segment or a physically adsorbed surfactant (sodium dodecyl sulfate, SDS). By fitting the experimental SANS data and combining with gravimetry experiments, we have ascertained the hydrophilic species distribution within the drying film and followed its evolution by correlating the size and shape of stabilizer clusters with the drying time. The evolution of the SDS distribution over drying time is being driven by a reduction in the interfacial free energy. However, the PMAA-based stabilizer macromolecules are restricted by their covalent bonding to core polymer chains and hence form high-surface area disclike phases at the common boundary between particles and PMAA micelles. Contrary to an idealized view of film formation, PMAA does not remain in the walls of a continuous honeycomb structure. The results presented here shed new light on the nanoscale distribution of hydrophilic species in drying and ageing latex films. We provide valuable insights into the influence of the stabilizer mobility on the final structure of latex films.

    AS Clough, PM Jenneson, JL Keddie (1997)Ion beam analysis of small molecule diffusion in polymers, In: ANTEC'97 - PLASTICS SAVING PLANET EARTH, CONFERENCE PROCEEDINGS, VOLS 1 - 3pp. 2211-2215 SOC PLASTICS ENGINEERS
    M. Schulz, J.L. Keddie (2018)A Critical and Quantitative Review of the Stratification of Particles during the Drying of Colloidal Films, In: Soft Matter14pp. 6181-6197 Royal Society of Chemistry

    For a wide range of applications, films are deposited from colloidal particles suspended in a volatile liquid. There is burgeoning interest in stratifying colloidal particles into separate layers within the final dry film to impart properties at the surface different to the interior. Here, we outline the mechanisms by which colloidal mixtures can stratify during the drying process. The problem is considered here as a three-way competition between evaporation of the continuous liquid, sedimentation of particles, and their Brownian diffusion. In particle mixtures, the sedimentation of larger or denser particles offers one means of stratification. When the rate of evaporation is fast relative to diffusion, binary mixtures of large and small particles can stratify with small particles on the top, according to physical models and computer simulations. We compare experimental results found in the scientific literature to the predictions of several recent models in a quantitative way. Although there is not perfect agreement between them, some general trends emerge in the experiments, simulations and models. The stratification of small particles on the top of a film is favoured when the colloidal suspension is dilute but when both the concentration of the small particles and the solvent evaporation rate are sufficiently high. A higher ratio also favours stratification by size. This review points to ways that microstructures can be designed and controlled in colloidal materials to achieve desired properties.

    E Daar, E Woods, JL Keddie, A Nisbet, DA Bradley (2010)Effect of penetrating ionising radiation on the mechanical properties of pericardium, In: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT619(1-3)pp. 356-360
    J Selvakumaran, JL Keddie, DJ Ewins, MP Hughes (2008)Protein adsorption on materials for recording sites on implantable microelectrodes, In: JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE19(1)pp. 143-151 SPRINGER

    Implantable microelectrodes have the potential to become part of neural prostheses to restore lost nerve function after nerve damage. The initial adsorption of proteins to materials for implantable microelectrodes is an important factor in determining the longevity and stability of the implant. Once an implant is in the body, protein adsorption takes place almost instantly before the cells reach the surface of an implant. The aim of this study was to identify an optimum material for electrode recording sites on implantable microelectrodes. Common materials for electrode sites are gold, platinum, iridium, and indium tin oxide. These, along with a reference material (titanium), were investigated. The thickness and the structure of adsorbed proteins on these materials were measured using a combination of atomic force microscopy and ellipsometry. The adsorbed protein layers on gold (after 7 and 28 days of exposure to serum) were the smoothest and the thinnest compared to all the other substrate materials, indicating that gold is the material of choice for electrode recording sites on implantable microelectrodes. However, the results also show that indium tin oxide might also be a good choice for these applications.

    I Jurewicz, P Worajittiphon, AA King, PJ Sellin, JL Keddie, AB Dalton (2011)Locking carbon nanotubes in confined lattice geometries--a route to low percolation in conducting composites., In: J Phys Chem B115(20)pp. 6395-6400

    A significant reduction in the electrical percolation threshold is achieved by locking carbon nanotubes (CNTs) in a predominantly hexagonally close-packed (HCP) colloidal crystal lattice of partially plasticized latex particles. Contrary to other widely used latex processing where CNTs are randomly distributed within the latex matrix, for the first time, we show that excluding CNTs from occupying the interior volume of the latex particles promotes the formation of a nonrandom segregated network. The electrical percolation threshold is four times lower in an ordered segregated network made with colloidal particles near their glass transition temperature (T(g)) in comparison to in a random network made with particles at a temperature well above the T(g). This method allows for a highly reproducible way to fabricate robust, stretchable, and electrically conducting thin films with significantly improved transparency and lattice percolation at a very low CNT inclusion which may find applications in flexible and stretchable electronics as well as other stretchable technologies. For instance, our technology is particularly apt for touch screen applications, where one needs homogeneous distribution of the conductive filler throughout the matrix.

    B Newling, PM Glover, JL Keddie, DM Lane, PJ McDonald (1997)Concentration profiles in creaming oil-in-water emulsion layers determined with stray field magnetic resonance imaging, In: LANGMUIR13(14)pp. 3621-3626 AMER CHEMICAL SOC
    J Mallegol, JP Gorce, O Dupont, C Jeynes, PJ McDonald, JL Keddie (2002)Origins and effects of a surfactant excess near the surface of waterborne acrylic pressure-sensitive adhesives, In: LANGMUIR18(11)pp. 4478-4487 AMER CHEMICAL SOC
    F Deplace, J Marchal, C Carelli, A Chateauminois, C Creton, M Rabjohns, A Foster, PA Lovell, C Lei, J Keddie (2009)Soft-soft nanocomposites for adhesive applications, In: 12th International Conference on Fracture 2009, ICF-122pp. 1205-1211
    TRE Simpson, JL Keddie, B Parbhoo (2003)Influence of interfaces on the rate of crosslinking in silicone coatings., In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY225pp. U710-U710
    JL Keddie, E Ciampi, PJ McDonald, JM Salamanca (1999)Magnetic resonance imaging of the film formation of waterborne coatings., In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY218pp. U621-U621 AMER CHEMICAL SOC
    JL Keddie (2001)Structural analysis of organic interfacial layers by ellipsometry, In: CURRENT OPINION IN COLLOID & INTERFACE SCIENCE6(2)pp. 102-110 ELSEVIER SCIENCE LONDON
    Zoe L. Bushell, Christopher A. Broderick, Lukas Nattermann, Rita Joseph, Joseph L. Keddie, Judy M. Rorison, Kerstin Volz, Stephen J. Sweeney (2019)Giant bowing of the band gap and spin-orbit splitting energy in GaP1−χBiχ dilute bismide alloys, In: Scientific Reports9(1)6835 Nature Research

    Using spectroscopic ellipsometry measurements on GaP1−χBiχ/GaP epitaxial layers up to χ = 3.7% we observe a giant bowing of the direct band gap (EΓg) and valence band spin-orbit splitting energy (ΔSO). EΓg (ΔSO) is measured to decrease (increase) by approximately 200 meV (240 meV) with the incorporation of 1% Bi, corresponding to a greater than fourfold increase in ΔSO in going from GaP to GaP0.99Bi0.01. The evolution of EΓg and ΔSO with χ is characterised by strong, composition-dependent bowing. We demonstrate that a simple valence band-anticrossing model, parametrised directly from atomistic supercell calculations, quantitatively describes the measured evolution of EΓg and ΔSO with χ. In contrast to the well-studied GaAs1−χBiχ alloy, in GaP1−χBiχ substitutional Bi creates localised impurity states lying energetically within the GaP host matrix band gap. This leads to the emergence of an optically active band of Bi-hybridised states, accounting for the overall large bowing of EΓg and ΔSO and in particular for the giant bowing observed for χ ≲ 1%. Our analysis provides insight into the action of Bi as an isovalent impurity, and constitutes the first detailed experimental and theoretical analysis of the GaP1−χBiχ alloy band structure.

    S McMurtry, JD Wright, DA Jackson, JL Keddie (2000)Humidity sensing using PMMA-PMTGA-PMMA polymer in low coherence interferometric system, In: ELECTRONICS LETTERS36(1)pp. 73-74 IEE-INST ELEC ENG
    A Georgiadis, FN Muhamad, A Utgenannt, JL Keddie (2013)Aesthetically textured, hard latex coatings by fast IR-assisted evaporative lithography, In: Progress in Organic Coatings76(12)pp. 1786-1791 Elsevier

    Polymer coatings with periodic topographic patterns, repeating over millimetre length scales, can be created from lateral flows in an aqueous dispersion of colloidal particles. The flow is driven by differences in evaporation rate across the wet film surface created by IR radiative heating through a shadow mask. This new process, which we call IR radiation-assisted evaporative lithography (IRAEL), combines IR particle sintering with the concept of evaporative lithography. Here, a series of experiments has been conducted in which the mass of the latex is measured as a function of the exposure time under infrared radiation through a mask. The water evaporation rates and the minimum exposure time required for a dry film are estimated as a function of the power density of the IR emitter. The temperature of the wet film is monitored to avoid overheating and boiling of the water, which will otherwise cause defects. It is demonstrated that textured films can be created on a variety of substrates (plastics, metals, paper and glass), and processing times can be as short as 5 min. We use IRAEL to decorate household goods with an aesthetic coating with the desired texture. © 2013 Elsevier B.V. All rights reserved.

    Ronald P. White, Yutaka Aoki, Julia S. Higgins, Joseph L. Keddie, Jane E. G. Lipson, Joao T. Cabral (2020)Thermodynamics of model PaMSAN/dPMMA blend: a combined study by SANS, ellipsometry and locally correlated lattice (LCL) theory, In: Macromolecules American Chemical Society

    We combine experiment and theory to elucidate how small, local, structural changes can impact miscibility in polymer blends. Small-angle neutron scattering (SANS) experiments yield both the phase boundaries and the temperature dependence of the second derivative of the free energy of mixing. We demonstrate here, for the first time, that a fundamental characterization of pure component properties can be achieved through ellipsometry measurements on films of pure polymers (thickness ∼200 nm) to provide key data on the volume (or thickness)–temperature relationships; this development is significant given the scarcity of precise pressure–volume–temperature (PVT) data on pure polymers and blends. The experimental measurements allow us to undertake a detailed thermodynamic analysis of mixing using the locally correlated lattice (LCL) theory, which has been shown to be effective in rationalizing blend miscibility in terms of the pure component properties. We focus here on polymer blends of poly(α-methyl styrene-co-acrylonitrile) (PαMSAN) with deuterated poly(methyl methacrylate) (dPMMA), which differ in the degree of tacticity in the dPMMA component (atactic or syndiotactic), leading to an increase in miscibility for the latter. By combining LCL analysis of pure and mixed systems, we are able to connect tacticity changes to shifts in local nonbonded interactions, in free volume, and in thermal expansion coefficients, which in turn impact the thermodynamic compatibility of the blend components.

    T Wang, CD de las Heras Alarcon, M Goikoetxea, I Beristain, M Paulis, MS Barandiaran, JM Asua, JL Keddie (2010)Cross-Linked Network Development in Compatibilized Alkyd/Acrylic Hybrid Latex Films for the Creation of Hard Coatings, In: Langmuir: the ACS journal of surfaces and colloids26(17)pp. 14323-14333 American Chemical Society
    H Richardson, M Sferrazza, JL Keddie (2003)Influence of the glass transition on solvent loss from spin-cast glassy polymer thin films, In: EUROPEAN PHYSICAL JOURNAL E12pp. S87-S91 SPRINGER
    Iñigo Díez-García, Joseph L. Keddie, Arantxa Eceiza, Agnieszka Tercjak (2020)Optimization of adhesive performance of waterborne poly(urethane-urea)s for adhesion on high and low surface energy surfaces, In: Progress in Organic Coatings140105495 Elsevier

    Achieving adhesion to materials with a low surface energy is a challenge when designing new soft adhesives.With this question in mind, waterborne poly(urethane-urea) (WPUU) dispersions based on poly(ethylene oxide)(PEO) homopolymer and poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (PEO-b-PPO-b-PEO) and poly(propylene oxide-b-ethylene oxide-b-propylene oxide) (PPO-b-PEO-b-PPO) triblock copolymers were prepared. Adhesives cast from the dispersions exhibited better adhesion on a low surface energy polypropylene (PP) probe than on a high surface energy steel probe. Moreover, with the aim of improving the adhesive performance of the WPUUs for pressure sensitive adhesive (PSA) applications, bilayer systems were designed. They were prepared using two WPUUs with differing viscoelastic behavior (one more solid-like and the other one, more liquid-like)to create a gradient in the viscoelastic properties. This strategy led to adhesive materials that exhibited fibrillation during probe tack measurements using a steel probe, which is typical of PSAs. Finally, prototype adhesive tapes were prepared from one of the bilayer systems. These adhesive tapes performed in a peel test in a similar way as a domestic commercial adhesive tape, making them interesting for that potential application.

    JL Keddie, P Meredith, RAL Jones, AM Donald (1996)Rate-limiting steps in film formation of acrylic latices as elucidated with ellipsometry and environmental scanning electron microscopy, In: FILM FORMATION IN WATERBORNE COATINGS648pp. 332-348 AMER CHEMICAL SOC
    J Mallégol, JL Keddie, O Dupont (2001)Etude structurale des films d'adhesifs acryliques sensibles a la pression par microscopie a force atomique en mode tapping, In: Vide: Science, Technique et Applications(302 SU)pp. 34-37
    A Tzitzinou, JL Keddie, JL Geurts, M Mulder, R Satguru, KE Treacher (2001)Molecular weight effects on the film formation of latex and on surfactant distribution and morphology, In: ACS Symposium Series790pp. 58-87

    It is well known that viscosity, self-diffusion coefficient and glass transition temperature are a strong function of molecular weight (MW). Here we report the film formation characteristics of an acrylic (BMA/MMA/MAA) latex as a function of its average MW, considering four molecular weights ranging from 7,500 to 705,000 Daltons. As a means of taking into account the lower glass transition temperature and viscosity expected in the lower MW latices, we compare the film formation behaviours at the same temperature increment above their respective minimum film formation temperatures (MFT). We find that the lower MW latices form a film with a lower void concentration and lower surface roughness in comparison to the higher MW latices at the same temperature relative to the MFT. Non-invasive analysis of the film formation using ellipsometry finds evidence for void formation in the high MW latex (Mw = 705, 000 Daltons) up to 30°C above MFT. In contrast, the lowest MW latex (Mw = 7,500 Daltons) forms a dense film with few, if any, voids immediately upon the evaporation of water and at temperatures as low as 5°C above MFT. These differences can be partly attributed to varying degrees of plasticization by water. In addition, the film morphology at the polymer/air interface was investigated using atomic force microscopy. Surface features were attributed to the presence of surfactant. A low MW latex shows surfactant features at a lower film formation temperature (relative to the MFT) and/or a shorter film-formation time in comparison to the high MW latex.

    TRE Simpson, B Parbhoo, JL Keddie (2003)The dependence of the rate of crosslinking in poly(dimethyl siloxane) on the thickness of coatings, In: POLYMER44(17)pp. 4829-4838 ELSEVIER SCI LTD
    Philip Richardson, Ignacio Martín-Fabiani, Patrick Shaw, Eman Alsaffar, Emilie Velasquez, Paul Gardner, Peter Shaw, James Michael Adams, Joseph L. Keddie (2019)Competition between Crystallization and Coalescence during the Film Formation of Poly(Chloroprene) Latex and Effects on Mechanical Properties, In: Industrial & Engineering Chemistry Research58(46)pp. 21031-21043 American Chemical Society

    Poly(chloroprene) is a synthetic crystallizable polymer used in several applications, including rubber gloves. The film formation of poly(chloroprene) latex offers opportunities to define structures at length scales between the molecular and macroscopic, thereby adjusting the elastomer’s mechanical properties. However, the connections between processing and the resultant film properties are not fully understood. Here, we investigate the competition between the coalescence of latex particles to build cohesive strength and their crystallization to raise the elastic modulus. We demonstrate that when coalescence precedes crystallization, the elastomer has greater extensibility and a higher tensile strength compared to when crystallization occurs during coalescence. The mechanical properties of poly(chloroprene) were tuned by blending two colloids with differing gel contents and crystallizabilities. Heating above poly(chloroprene)’s melting temperature allows increased particle interdiffusion and builds cohesion, prior to recrystallization. We provide evidence from in situ wide-angle X-ray scattering for the strain-induced crystallization of as-cast films from particle blends.

    DC Andrei, JN Hay, JL Keddie, RP Sear, SG Yeates (2000)Surface levelling of thermosetting powder coatings: theory and experiment, In: JOURNAL OF PHYSICS D-APPLIED PHYSICS33(16)pp. 1975-1981 IOP PUBLISHING LTD
    PJ McDonald, E Ciampi, JL Keddie, M Heidenreich, R Kimmich (1999)Magnetic-resonance determination of the spatial dependence of the droplet size distribution in the cream layer of oil-in-water emulsions: Evidence for the effects of depletion flocculation, In: Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics59(1)pp. 874-884 The American Physical Society

    It is shown that a combination of pulsed-field-gradient spin-echo ~PGSE! nuclear-magnetic-resonance~NMR! restricted diffusion analysis and NMR imaging may be used to measure the spatial dependence of the droplet size distribution in the cream layer of turbid oil-in-water emulsions. 1H-13C cyclic J cross-polarization PGSE is introduced as a technique for this purpose in cases where selective observation of the oil component ~or other carbohydrate constituent! is required. With this method, 13C nuclei are chemical shift selectively excited by cross-polarization from coupled 1H partners. An optimum detection sensitivity is ensured by transferring the polarization back to the coupled protons with which the combined imaging and diffusion experiment is then carried out. The spatial dependence of the oil droplet size distribution was measured for a series of emulsions containing various fractions of gum xanthan thickener dissolved in the water. The experimental results are compared with a recent model of the creaming process due to Pinfield, Dickinson, and Povey @J. Colloid Interface Sci. 166, 363 ~1994!#. When no gum xanthan is present, the experimental results are in good agreement with the model. However, the model fails to describe the droplet distribution for emulsions with a gum xanthan concentration of the order of 0.1 wt %. The discrepancy is discussed in terms of depletion flocculation and depletion stabilization.

    JL Keddie, RA Cory, RAL Jones (1998)Polymer dynamics in thin films, In: MODERN ASPECTS OF COLLOIDAL DISPERSIONSpp. 149-157
    Andrea Fortini, Ignacio Martin-Fabiani, Jennifer Lesage De La Haye, Pierre-Yves Dugas, Muriel Lansalot, Franck D'Agosto, Elodie Bourgeat-Lami, Joseph Keddie, Richard Sear (2016)Dynamic stratification in drying films of colloidal mixtures, In: Physical Review Letters116(11) American Physical Society

    In simulations and experiments, we study the drying of films containing mixtures of large and small colloidal particles in water. During drying, the mixture stratifies into a layer of the larger particles at the bottom with a layer of the smaller particles on top. We developed a model to show that a gradient in osmotic pressure, which develops dynamically during drying, is responsible for the segregation mechanism behind stratification.

    T Wang, C-H Lei, AB Dalton, M Manea, JM Asua, JL Keddie (2007)COLL 306-Waterborne nanocomposite pressure-sensitive adhesives: Achieving enhanced adhesion combined with electrical conductivity, In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY233 AMER CHEMICAL SOC
    Y Zhao, JD Carey, N Knoops, D Maetens, I Hopkinson, JN Hay, JL Keddie (2002)Inhibition of the surface levelling of thermosetting polyester powder coatings caused by surface tension gradients, In: Journal of Materials Science37(22)pp. 4759-4768 Springer

    Previous theoretical and experimental work has shown that surface tension gradients in liquid layers create surface defects and inhibit the levelling of an uneven surface. In coatings deposited from thermosetting polyester powders, which are studied here, small amounts of a low molecular-weight acrylate are incorporated to act as a “flow agent.” We find that this additive lowers the surface tension of the polymer melt and has a minor effect on the melt viscosity. A slower rate of levelling results from the decreased surface tension. We provide experimental evidence that lateral gradients in the surface tension of the polymer melt, resulting from the non-uniform distribution of the flow agent, inhibit the levelling of the surface. Specifically, the surface roughness of a powder coating is up to three times greater when a steep surface tension gradient is purposely created through powder blending. Surface tension gradients might also be responsible for the greater surface roughness (observed with atomic force microscopy on lateral length scales of 100 μm) that is found in coatings that contain flow agent.

    A Lopez, E Degrandi-Contraires, E Canetta, C Creton, JL Keddie, JM Asua (2011)Waterborne Polyurethane-Acrylic Hybrid Nanoparticles by Miniemulsion Polymerization: Applications in Pressure-Sensitive Adhesives, In: LANGMUIR27(7)pp. 3878-3888 AMER CHEMICAL SOC
    J Mallegol, G Bennett, PJ McDonald, JL Keddie, O Dupont (2006)Skin development during the film formation of waterborne acrylic pressure-sensitive adhesives containing tackifying resin, In: J ADHESION82(3)pp. 217-238 TAYLOR & FRANCIS LTD
    NP Barradas, JL Keddie, R Sackin (1999)Bayesian inference analysis of ellipsometry data, In: Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics59(5)pp. 6138-6151

    Variable angle spectroscopic ellipsometry is a nondestructive technique for accurately determining the thicknesses and refractive indices of thin films. Experimentally, the ellipsometry parameters ψ and Δ are measured, and the sample structure is then determined by one of a variety of approaches, depending on the number of unknown variables. The ellipsometry parameters have been inverted analytically for only a small number of sample types. More general cases require either a model-based numerical technique or a series of approximations combined with a sound knowledge of the test sample structure. In this paper, the combinatorial optimization technique of simulated annealing is used to perform least-squares fits of ellipsometry data (both simulated and experimental) from both a single layer and a bilayer on a semi-infinite substrate using what is effectively a model-free system, in which the thickness and refractive indices of each layer are unknown. The ambiguity inherent in the best-fit solutions is then assessed using Bayesian inference. This is the only way to consistently treat experimental uncertainties along with prior knowledge. The Markov chain Monte Carlo algorithm is used. Mean values of unknown parameters and standard deviations are determined for each and every solution. Rutherford backscattering spectrometry is used to assess the accuracy of the solutions determined by these techniques. With our computer analysis of ellipsometry data, we find all possible models that adequately describe that data. We show that a bilayer consisting of a thin film of poly(styrene) on a thin film of silicon dioxide on a silicon substrate results in data that are ambiguous; there is more than one acceptable description of the sample that will result in the same experimental data.

    T Wang, C-H Lei, D Liu, M Manea, JM Asua, C Creton, AB Dalton, JL Keddie (2008)A molecular mechanism for toughening and strengthening waterborne nanocomposites, In: Advanced Materials20(1)pp. 90-94
    NA Nikonenko, IA Bushnak, JL Keddie (2009)Spectroscopic ellipsometry of mucin layers on an amphiphilic diblock copolymer surface, In: Applied Spectroscopy63(8)pp. 889-898 Sage

    Both visible and infrared (IR) spectroscopic ellipsometry have been employed to study the structure of thin layers of bovine submaxillary mucin (BSM) adsorbed on poly(acrylic acid-block-methyl methacrylate) (PAA-b-PMMA) copolymer and poly(methyl methacrylate) (PMMA) surfaces at three pH values (3, 7, and 10). The adsorbed mucin layer on the copolymer surface had the greatest thickness (17 nm) when adsorbed from a mucin solution at a pH of 3. For the first time, IR ellipsometry was used to identify adhesive interactions and conformational changes in mucin/polymer double layers. After applying the regularized method of deconvolution in the analysis, the formation of hydrogen bonds between the carboxyl groups of the BSM and PAA-b-PMMA copolymer in double layers has been found. The IR ellipsometry data, in agreement with the visible ellipsometry analysis, indicate the pH dependence of adhesion of mucin to the copolymer surface. There is an increase in the amount of hydrogen-bonded carboxyl groups in mucin deposited at a pH of 3. There is no evidence that the amide groups of the mucin participate in this bonding. At the lower pH, the IR ellipsometry spectra after deconvolution reveal an increase in the proportion of β-sheets in the BSM upon adsorption on the copolymer surface, indicating a more unfolded, aggregated structure. The IR ellipsometry data also indicated some changes in the conformational states of the side groups in the copolymer induced by entanglements and bonding interactions with the mucin macromolecules. Deconvolution provides an unprecedented level of information from the IR ellipsometry spectra and yields important insights. © 2009 Society for Applied Spectroscopy.

    D Styrkas, SJ Doran, T Gilchrist, JL Keddie, JR Lu, E Murphy, R Sackin, TJ Su, A Tzitzinou (1999)Application of ellipsometry to polymers at interfaces and in thin films, In: POLYMER SURFACES AND INTERFACES IIIpp. 1-42
    J Mallegol, O Dupont, JL Keddie (2003)Morphology and elasticity of waterborne acrylic pressure-sensitive adhesives investigated, with atomic force microscopy, In: JOURNAL OF ADHESION SCIENCE AND TECHNOLOGY17(2)pp. 243-259

    The morphology of pressure sensitive adhesives (PSAs), especially at the surface in contact with a release liner, is expected to have a dominant influence on the tack strength and energy in an application. We have used tapping-mode atomic force microscopy to determine the morphology at the surfaces of freshly-cast waterborne acrylic PSAs over lateral length scales of a few m. We demonstrate that topographical features on silicone release liners can be used to pattern the PSA surface in contact with it. Control of the texture of a PSA surface can potentially be exploited to tailor its properties. Latex particle boundaries are much better defined at the air surface of the PSA in comparison to its back face. A series of experiments suggests that this difference results from the distribution of water-soluble species within the dry film. The pressures and processes involved in the transfer lamination process do not alter the PSA morphology. The first reported AFM images of the response of these materials to pressure and shear provide insight into the deformation mechanisms. Amplitude-distance curves on PSA surfaces show that there is a small decrease in tack and an increase in stiffness after ageing for 13 months.

    TRE Simpson, Z Tabatabaian, C Jeynes, B Parbhoo, JL Keddie (2004)Influence of interfaces on the rates of crosslinking in poly(dimethyl siloxane) coatings, In: JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY42(6)pp. 1421-1431 JOHN WILEY & SONS INC
    J Selvakumaran, MP Hughes, JL Keddie, DJ Ewins (2002)Assessing biocompatibility of materials for implantable microelectrodes using cytotoxicity and protein adsorption studies, In: 2ND ANNUAL INTERNATIONAL IEEE-EMBS SPECIAL TOPIC CONFERENCE ON MICROTECHNOLOGIES IN MEDICINE & BIOLOGY, PROCEEDINGSpp. 261-264
    H Richardson, M Sferrazza, JL Keddie (2003)Slow relaxation of spin-cast poly(methyl methacrylate) confined in thin films, In: Materials Research Society Symposium - Proceedings790pp. 251-256 Materials Research Society
    JL Keddie, A Georgiadis, H Sansom, F Muhamad (2013)Bespoke patterned coatings via infrared radiation-assisted evaporative lithography: Moving colloids with modulated light, In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY245
    JL Keddie, R Gurney, D Dupin, E Siband (2013)Large-area patterning of the tackiness of a colloidal nanocomposite adhesive by sintering of nanoparticles under IR radiation, In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY245
    JM Salamanca, E Ciampi, DA Faux, PM Glover, PJ McDonald, AF Routh, ACIA Peters, R Satguru, JL Keddie (2001)Lateral drying in thick films of waterborne colloidal particles, In: LANGMUIR17(11)pp. 3202-3207 AMER CHEMICAL SOC
    JP Gorce, D Bovey, PJ McDonald, P Palasz, D Taylor, JL Keddie (2002)Vertical water distribution during the drying of polymer films cast from aqueous emulsions, In: EUROPEAN PHYSICAL JOURNAL E8(4)pp. 421-429 SPRINGER-VERLAG
    Benjamin Voogt, Henk Huinink, Sebastiaan J.F. Erich, Jurgen Scheerder, Paul Venema, Joseph L. Keddie, Olaf C.G. Adan (2019)Film formation of high Tg latex using hydroplasticization: Explanations from NMR relaxometry, In: Langmuir35(38)pp. 12418-12427 American Chemical Society

    The film formation of acrylic latex dispersions, containing different amounts of carboxylic acid functional groups by the incorporation of methacrylic acid (MAA), was studied with GARField 1H NMR at various relative humidities (RH). Polymer particles with glass transition temperatures in the range from 26 to 50 °C formed films at room temperature, because of hydroplasticization. It was found that with increased drying rate due to lower RH, the evaporation flux of water was limited by the latex polymer. Only in the second stage of drying this phenomenon was more obvious with increasing MAA content. 1H NMR relaxometry was used to study the change of hydrogen mobilities during film formation and hardening of the films. This showed that the drying rate itself had no impact on the hydrogen mobility in the latex films as measured via the T2 relaxation time. Hydrogen mobilities of water and the mobile polymer phase only significantly decrease after most water has evaporated. This implies that the rigidity of the polymers increases with the evaporation of water that otherwise plasticizes the polymer through hydrogen bonding with the carboxylic acid groups. This hardening of the polymer phase is essential for applications in a coating. The hydrogen mobilities were affected by the MAA concentration. Densities of mobile hydrogens increase with increasing MAA content. This is expected if the mobile protons are contained in the MAA groups. The result thus confirms the role of carboxylic acid groups in hydrogen bonding and plasticization of the copolymers. Hydrogen mobilities, however, decrease with increasing MAA content, which is hypothesized to be caused by the formation of dimers of carboxylic acid groups that still hold water. They still enable short range polymer hydrogen mobility due to hydroplasticization, but limit the long range polymer mobility due to interaction between the carboxylic acid groups.

    P Duckworth, H Richardson, C Carelli, JL Keddie (2005)Infrared ellipsometry of interdiffusion in thin films of miscible polymers, In: SURFACE AND INTERFACE ANALYSIS37(1)pp. 33-41 JOHN WILEY & SONS LTD

    A new application of infrared ellipsometry is reported. Specifically, the interdiffusion between thin films of miscible polymers - poly(methyl methacrylate) and poly(vinylidene fluoride) - is detected in a non-invasive measurement. A novel technique of data analysis for interdiffusion was developed and is described. The validity of the approach is supported by simulations of diffusion in a bilayer. The onset of extensive interdiffusion over a time period of 15 min occurs at a temperature of 160°C. At a temperature of 190°C, the data show that complete mixing of a bilayer (850 nm thick) occurs within 30s, which is consistent with previously reported values of the mutual diffusion coefficient. Infrared ellipsometry is non-invasive, applicable at elevated temperatures and relatively fast and sensitive. Although, in these measurements, it was unable to determine a concentration profile at the interface, infrared ellipsometry was used successfully to detect when interdiffusion had occurred. Hence, it is a useful means for screening polymer pairs for miscibility. Copyright © 2004 John Wiley & Sons, Ltd.

    R Udagama, CDLH Alarcon, JL Keddie, JG Tsavalas, E Bourgeat-Lami, TFL McKenna (2014)Acrylic-Alkyd Hybrids: Secondary Nucleation, Particle Morphology, and Limiting Conversions, In: MACROMOLECULAR REACTION ENGINEERING8(9)pp. 622-638 WILEY-V C H VERLAG GMBH
    J Mallegol, AM Barry, E Ciampi, PM Glover, PJ McDonald, JL Keddie, M Wallin, A Motiejauskaite, PK Weissenborn (2002)Influence of drier combination on through-drying in waterborne alkyd emulsion coatings observed with magnetic resonance profiling, In: JOURNAL OF COATINGS TECHNOLOGY74(933)pp. 113-124 FEDERATION SOC COATING TECH
    H Richardson, C Carelli, JL Keddie, M Sferrazza (2003)Structural relaxation of spin-cast glassy polymer thin films as a possible factor in dewetting., In: Eur Phys J E Soft Matter12(3)pp. 437-440 Springer

    Reiter has recently reported a situation in which the dewetting of quasi-solid films is linked to plastic deformation--rather than viscous flow--resulting from capillary forces. Herein we propose that, in thin films of some glassy polymers--especially poly(methyl methacrylate) (PMMA)--prepared by spin-casting from solvent, structural relaxation might impart sufficient stress to cause plastic deformation. We find that PMMA films decrease in thickness by several percent, which is sufficient to create significant stress in those cases in which the film is attached to a rigid substrate. The floating technique, which can take tens of minutes, might allow most of the structural relaxation to occur prior to dewetting experiments.

    AC Hellgren, M Wallin, PK Weissenborn, PJ McDonald, PM Glover, JL Keddie (2001)New techniques for determining the extent of crosslinking in coatings, In: PROGRESS IN ORGANIC COATINGS43(1-3)pp. 85-98
    A Lopez, Y Reyes, JM Asua, A Lopez, E Degrandi-Contraires, C Creton, E Canetta, JL Keddie, E Canetta (2013)Simultaneous free-radical and addition miniemulsion polymerization: Effect of the chain transfer agent on the microstructure of polyurethane-acrylic pressure-sensitive adhesives, In: Macromolecular Materials and Engineering298(1)pp. 53-66 Wiley-VCH Verlag Berlin

    The effects of the CTA concentration on polymerization kinetics, polymer microstructure, particle morphology, and adhesive performance of waterborne hybrid PSAs prepared by simultaneous free-radical and addition miniemulsion polymerizations are studied. The development of the microstructure is shown to differ from waterborne acrylic PSAs obtained by free-radical polymerization because of the contribution of the addition reaction, which in turn causes marked differences in the adhesive performance of the final films. A computer simulation is developed to obtain detailed information about the microstructure of PU/acrylic hybrids and to correlate the microstructure with the final adhesive properties. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

    JL Keddie, A Utgenannt, AG Kanaras, OL Muskens (2013)Directed organization of gold nanoparticles in polymer coatings over large length scales through infrared-assisted evaporative lithography, In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY245
    I López García, JL Keddie, M Sferrazza (2011)Some insights into the structural relaxation of spin-cast, glassy polymer thin films, In: Polymer Journal43(2)pp. 214-217 Nature Publishing Group

    The widespread use of thin films in a range of applications and industries, from coatings, inks and lithography to nano-imprinting, optoelectronics and memory devices,1 has made the understanding of thin films, particularly the changes induced by structural relaxation and solvent evaporation, very important. There is a need to know whether a film will change in dimensions after its deposition and how fast these changes will occur.

    JL Keddie, JP Gorce, J Mallegol, M Wallin, AM Barry, E Ciampi, A Motiejauskaite, PM Glover, PJ McDonald, PK Weissenborn (2001)MR profiling of film formation and crosslinking in waterborne alkyd emulsions and emulsion paints., In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY222pp. U378-U378 AMER CHEMICAL SOC
    N Kessel, DR Illsley, JL Keddie (2008)The diacetone acrylamide crosslinking reaction and its influence on the film formation of an acrylic latex, In: JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH5(3)pp. 285-297 SPRINGER
    PM Jenneson, AS Clough, JL Keddie, JR Lu, P Meredith (1997)Non-ionic surfactant concentration profiles in undamaged and damaged hair fibres determined by scanning ion beam nuclear reaction analysis, In: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS132(4)pp. 697-703 ELSEVIER SCIENCE BV
    I López García, JL Keddie, M Sferrazza (2011)Probing the early stages of solvent evaporation and relaxation in solvent-cast polymer thin films by spectroscopic ellipsometry, In: Surface and Interface Analysis43(11)pp. 1448-1452 Wiley

    The formation of solvent-cast, poly(methyl methacrylate) (PMMA) thin films from dilute bromobenzene solutions was studied using an ellipsometry technique. Bromobenzene has a relatively high refractive index (compared to PMMA), which provides contrast in ellipsometry, allowing the concentration to be determined. The solvent also has a relatively low evaporation rate, which makes the film formation slow enough to capture via the technique. The formation of the glassy film is thus studied in situ, and information on solvent and void concentration in the thin film during the film formation process is obtained. There is evidence that nanovoids (representing intramolecular space) develop in the film when solvent evaporates.

    AM Koenig, TG Weerakkody, JL Keddie, D Johannsmann (2008)Heterogeneous drying of colloidal polymer films: Dependence on added salt, In: LANGMUIR24(14)pp. 7580-7589 American Chemical Society

    Using magnetic resonance profiling coupled with dynamic light scattering, we have investigated the mechanisms leading to the formation of a partly coalesced surface layer, or “open skin”, during film formation from waterborne polymer dispersions. We present the first use of the skewness of the distribution of free water as a model-free indicator of the spatial nonuniformity of drying. The skewness reaches a maximum at the same time at which a strong, static component, presumably originating from a skin at the film/air interface, appears in the light scattering data. Addition of salt to the dispersion increases both the skewness of the distribution of free water and the propensity for skin formation. Surprisingly, the drying is influenced not only by the concentration and valency of the ions in the salt but also by the particular ion. At intermediate particle densities, added salt strongly lowers the cooperative diffusion coefficient, Dcoop. When the particles reach close packing, Dcoop sharply increases. If the particles readily coalesce, the effects of the increased diffusivity will be counteracted, thereby inducing the formation of a skin. A modified Peclet number, Pe, using Dcoop, is proposed, so that the presence of salt is explicitly considered. This modified Pe is able to predict the nonuniformity in drying that leads to skin formation.

    N Akram, M Ishaq, M Zuber, RS Gurney, JL Keddie (2013)Influence of Polyol Molecular Weight and Type on the Tack and Peel Properties of Waterborne Polyurethane Pressure-Sensitive Adhesives, In: Macromolecular Reaction Engineering7(10)pp. 493-503

    A requirement for optimum performance in a pressure-sensitive adhesive (PSA) is the right balance between viscous and elastic properties, achieved by controlling the molecular architecture. Here, waterborne polyurethane PSAs are synthesized using a blend of polyether and polyalkene-based polyols. The effects of the polyol type and molecular weight on the adhesive and thermomechanical properties are explored to optimize them for PSA applications. A linear polyurethane is synthesized by the reaction of an aliphatic diisocyanate with a diol blend of polypropylene glycol (PPG) and hydroxyl-terminated polybutadiene (HTPB). With increasing concentrations of flexible HTPB segments and the associated increased viscous dissipation a favorable increase in the tack adhesion energy and peel strength is obtained. Adhesive properties are improved with increasing PPG molecular weight because chain entanglements become possible in the soft segments and raise the storage modulus. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

    P Ekanayake, PJ McDonald, JL Keddie (2009)An experimental test of the scaling prediction for the spatial distribution of water during the drying of colloidal films, In: EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS166(1)pp. 21-27
    MA Bero, WB Gilboy, PM Glover, JL Keddie (1999)Three-dimensional radiation dose measurements with ferrous benzoic acid xylenol orange in gelatin gel and optical absorption tomography, In: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT422(1-3)pp. 617-620 ELSEVIER SCIENCE BV
    Y Holl, JL Keddie, PJ McDonald, WA Winnik (2001)Drying modes of polymer colloids, In: ACS Symposium Series790pp. 2-26

    This chapter reviews the complex step of drying in the latex film formation process. Drying modes have a profound effect on drying rates and on the final properties of films, primarily through their influence on film morphology and the distribution of water-soluble species. Three distinct drying modes (acting separately, successively or together) can be defined, namely homogeneous drying (in which the water concentration remains uniform in the sample throughout the drying process), drying normal to the surface (where a dry layer of increasing thickness develops from the air surface of the latex coating); and lateral drying (where dry areas increase in size in a direction parallel to the substrate). Details are given on the current knowledge and understanding of these drying modes. The last section of the chapter considers the main parameters controlling the drying modes, i.e. thickness and geometric effects, the structure and rheology of the dispersion, particle viscoelasticity, and the overall rate of water loss.

    WL Chen, KR Shull, T Papatheodorou, DA Styrkas, JL Keddie (1999)Equilibrium swelling of hydrophilic polyacrylates in humid environments, In: MACROMOLECULES32(1)pp. 136-144 AMER CHEMICAL SOC
    JL Keddie (1997)Film formation of latex, In: MATERIALS SCIENCE & ENGINEERING R-REPORTS21(3)pp. 101-170 ELSEVIER SCIENCE SA
    A Cappellani, JL Keddie, NP Barradas, SM Jackson (1999)Processing and characterisation of sol-gel deposited Ta2O5 and TiO2-Ta2O5 dielectric thin films, In: SOLID-STATE ELECTRONICS43(6)pp. 1095-1099 PERGAMON-ELSEVIER SCIENCE LTD
    G Bennett, JP Gorce, JL Keddie, PJ McDonald, H Berglind (2003)Magnetic resonance profiling studies of the drying of film-forming aqueous dispersions and glue layers, In: MAGNETIC RESONANCE IMAGING21(3-4)pp. 235-241 ELSEVIER SCIENCE INC
    A Tzitzinou, PM Jenneson, AS Clough, JL Keddie, JR Lu, P Zhdan, KE Treacher, R Satguru (1999)Surfactant concentration and morphology at the surfaces of acrylic latex films, In: PROGRESS IN ORGANIC COATINGS35(1-4)pp. 89-99 ELSEVIER SCIENCE SA
    A Tzitzinou, JL Keddie, JM Geurts, ACIA Peters, R Satguru (2000)Film formation of latex blends with bimodal particle size distributions: Consideration of particle deformability and continuity of the dispersed phase, In: MACROMOLECULES33(7)pp. 2695-2708 AMER CHEMICAL SOC
    David Makepeace, P Locatelli, C Lindsay, James Adams, Joseph Keddie (2018)Colloidal Polymer Composites: Are Nano-Fillers Always Better for Improving Mechanical Properties?, In: Journal of Colloid and Interface Science523pp. 45-55 Elsevier

    Hypothesis Colloidal polymer composites, in which polymer particles are blended with a filler, are widely used in applications including pharmaceuticals, crop protection, inks, and protective coatings. It is generally found that the presence of hard particulate fillers will increase the elastic modulus of a polymer colloid composite. However, the influence of the size of the filler particle on the large-strain deformation and fracture and on the viscoelastic characteristics, including creep, is not well explored. We hypothesize that the size ratio of the filler to the colloidal polymer will play a critical role in determining the properties of the composite. Experiments Colloidal composites were prepared by blending soft polymer colloids (as a binder) with calcium carbonate fillers having four different sizes, spanning from 70 nm to 4.5 m. There is no bonding between the filler and matrix in the composites. The large-strain deformation, linear viscoelasticity, and creep were determined for each filler size for increasing the filler volume fractions (CC). Weibull statistics were used to analyze the distributions of strains at failure. Findings We find that the inclusion of nano-fillers leads to brittle fracture at a lower CC than when m-size fillers are used. The data interpretation is supported by Weibull analysis. However, for a given CC, the storage modulus is higher in the rubbery regime, and the creep resistance is higher when nanoparticles are used. Using scanning electron microscopy to support our arguments, we show that the properties of colloidal composites are correlated with their microstructure, which can be altered through control of the filler:polymer particle size ratio. Hard nanoparticles pack efficiently around larger particles to provide reinforcement (manifested as a higher storage modulus and greater creep resistance), but they also introduce weak points that lead to brittleness.

    DA Styrkas, V Butun, JR Lu, JL Keddie, SP Armes (2000)pH-controlled adsorption of polyelectrolyte diblock copolymers at the solid/liquid interface, In: LANGMUIR16(14)pp. 5980-5986 AMER CHEMICAL SOC
    T Wang, C-H Lei, AB Dalton, C Creton, Y Lin, KA Shiral Fernando, Y-P Sun, M Manea, JM Asua, JL Keddie (2006)Waterborne, nanocomposite pressure-sensitive adhesives with high tack energy, optical transparency, and electrical conductivity, In: ADVANCED MATERIALS18(20)pp. 2730-+ WILEY-V C H VERLAG GMBH
    Y Liu, W-J Soer, J Scheerder, G Satgurunathan, JL Keddie (2015)Water Vapor Sorption and Diffusion in Secondary Dispersion Barrier Coatings: A Critical Comparison with Emulsion Polymers, In: ACS Applied Materials and Interfaces7(22)pp. 12147-12157 American Chemical Society

    The conventional method for synthesizing waterborne polymer colloids is emulsion polymerization using surfactants. An emerging method is the use of secondary dispersions (SD) of polymers in water, which avoids the addition of any surfactant. Although there are numerous studies of the water barrier properties (sorption, diffusion, and permeability) of waterborne emulsion (Em) polymer coatings, the properties of SD coatings, in comparison, have not been thoroughly investigated. Here, dynamic water vapor sorption analysis is used to compare the equilibrium sorption isotherms of the two forms of styrene-acrylate copolymers (Em and SD) with the same monomer composition. From an analysis of the kinetics of vapor sorption, the diffusion coefficient of water in the polymer coatings is determined. The combined effects of particle boundaries and surfactant addition were investigated through a comparison of the properties of SD and Em coatings to those of (1) solvent-cast polymer coatings (of the same monomer composition), (2) Em polymers that underwent dialysis to partially remove the water-soluble species, and (3) SD polymers with added surfactants. The results reveal that both the particle boundaries and the surfactants increase vapor sorption. The diffusion coefficients of water are comparable in magnitude in all of the polymer systems but are inversely related to water activity because of molecular clustering. Compared to all of the other waterborne polymer systems, the SD barrier coatings show the lowest equilibrium vapor sorption and permeability coefficients at high relative humidities as well as the lowest water diffusion coefficient at low humidities. These barrier properties make SD coatings an attractive alternative to conventional emulsion polymer coatings.

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