Professor Joseph Keddie

Professor of Soft Matter Physics

Qualifications: BA, BS (Alfred, USA); MS, PhD (Cornell, USA), CPhys, FInstP, MIM

Email:
Phone: Work: 01483 68 6803
Room no: 04 BB 03

Further information

Biography

Joe Keddie is Professor of Soft Matter Physics within the Soft Matter Physics Group.

After graduating from Cornell University (USA), Joe Keddie spent two years as a post-doctoral researcher in the Polymer & Colloids Group at the Cavendish Laboratory, Cambridge followed by one year as an Oppenheimer Fellow. At Cambridge he used ellipsometry and environmental-SEM to study polymer colloids and thin films. In 1995 Joe moved to the University of Surrey as a Foundation Fund lecturer. Throughout his time at Surrey he has carried out research on soft matter, with special interest in polymer colloids. In recognition of his contributions to the understanding of polymer dynamics of polymers in thin films and colloidal dispersions, he was awarded the 2001 Paterson Medal and Prize by the Institute of Physics and named a Fellow. His research group won two Roon Awards from the Federation of Societies for Coatings Technology for papers presented at their Annual Meeting. In 2006 he was inducted into the Phi Beta Kappa honor society by his alma mater, Alfred University. A co-author of >100 journal articles and book chapters, he also holds two US patents and has recently submitted two international patent applications.  He has recently written - along with his co-author, Alex Routh, at the University of Cambridge - a book entitled Fundamentals of Latex Film Formation:  Processes and Properties.  This book was published in 2010 by Springer. In September 2011, he was elected the chair of the Institute of Physics Polymer Physics Group.

Research Interests

Professor Keddie is interested in fundamental processes in soft matter, especially polymer thin films, nanoparticles, and colloidal dispersions. Follow this link to see the active research topics of the Soft Matter Physics Group. Particular topics of recent research are

Along with others in the Soft Condensed Matter group, he uses several non-invasive probes, including atomic force microscopy, ellipsometry (both visible and IR), ion beam analysis and magnetic resonance profiling. He has particular expertise in the mechanisms by which polymer colloids form films and published a book on that topic in 2010.

Research Collaborations

Joe Keddie is currently collaborating with several European paint manufacturers and the University of Lyon in an FP7 project, called BARRIER-PLUS, which is developing new waterborne, nanocomposite coatings as barriers against corrosion.  He was previously a leader in two European projects (NsHAPe and NAPOLEON) concerning the development of improved waterborne, polymer coatings and adhesives through the control of their structure on the nanoscale. The NAPOLEON project has 21 partners, including nine from industry. He collaborates with Richard Sear and Alan Dalton in research on crystallisation and carbon nanotube/polymer composites. With Paul Sellin, he is developing the use of conjugated polymers for radiation detectors. A large fraction of his research has been supported by industries, including Cytec Specialty Chemicals (Drogenbos, Belgium), Akzo Nobel (Slough and Wilton), International Paint (Felling), BASF (Germany), Sun Chemicals (Orpington) and Dow Corning (Barry, South Wales). In recent projects, Joe has collaborated with Prof. Brian Vincent (Bristol), Costantino Creton (ESPCI, Paris), Prof. Jose' Asua (Univ. of the Basque Country, Spain),  Diethelm Johannsmann (Clausthal University of Technology), Prof. Ken Shull (Northwestern Univ.), Prof. Steve Armes (University of Sheffield), and Prof. Jian Lu (now at Manchester).

Publications

Highlights

  • Georgiadis A, Routh AF, Murray MW, Keddie JL. (2011) 'Bespoke periodic topography in hard polymer films by infrared radiation-assisted evaporative lithography'. Soft Matter, 7 (23), pp. 11098-11102.
  • Worajittiphon P, Jurewicz I, King AAK, Keddie JL, Dalton AB. (2010) 'Enhanced Thermal Actuation in Thin Polymer Films Through Particle Nano-Squeezing by Carbon Nanotube Belts'. ADVANCED MATERIALS, 22 (46), pp. 5310-5314.
  • Liu D, Wang T, Keddie JL. (2009) 'Protein Nanopatterning on Self-Organized Poly(styrene-b-isoprene) Thin Film Templates'. LANGMUIR, 25 (8), pp. 4526-4534.

    Abstract

    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.

  • Deplace F, Rabjohns MA, Yamaguchi T, Foster AB, Carelli C, Lei C-H, Ouzineb K, Keddie JL, Lovell PA, Creton C. (2009) 'Deformation and adhesion of a periodic soft-soft nanocomposite designed with structured polymer colloid particles'. SOFT MATTER, 5 (7), pp. 1440-1447.
  • Wang T, Colver PJ, Bon SAF, Keddie JL. (2009) 'Soft polymer and nano-clay supracolloidal particles in adhesives: synergistic effects on mechanical properties'. SOFT MATTER, 5 (20), pp. 3842-3849.
  • Wang T, Dalton AB, Keddie JL. (2008) 'Importance of Molecular Friction in a Soft Polymer-Nanotube Nanocomposite'. MACROMOLECULES, 41 (20), pp. 7656-7661.
  • Wang T, Lei C-H, Liu D, Manea M, Asua JM, Creton C, Dalton AB, Keddie JL. (2008) 'A molecular mechanism for toughening and strengthening waterborne nanocomposites'. ADVANCED MATERIALS, 20 (1), pp. 90-+.

Journal articles

  • Carter FT, Kowalczyk RM, Millichamp I, Chainey M, Keddie JL. (2014) 'Correlating particle deformation with water concentration profiles during latex film formation: reasons that softer latex films take longer to dry.'. Langmuir, United States: 30 (32), pp. 9672-9681.

    Abstract

    During the past two decades, an improved understanding of the operative particle deformation mechanisms during latex film formation has been gained. For a particular colloidal dispersion, the Routh-Russel deformation maps predict the dominant mechanism for particle deformation under a particular set of conditions (evaporation rate, temperature, and initial film thickness). Although qualitative tests of the Routh-Russel model have been reported previously, a systematic study of the relationship between the film-formation conditions and the resulting water concentration profiles is lacking. Here, the water distributions during the film formation of a series of acrylic copolymer latexes with varying glass-transition temperatures, Tg (values of -22, -11, 4, and 19 °C), have been obtained using GARField nuclear magnetic resonance profiling. A significant reduction in the rate of water loss from the latex copolymer with the lowest Tg was found, which is explained by its relatively low polymer viscosity enabling the growth of a coalesced skin layer. The set of processing parameters where the drying first becomes impeded occurs at the boundary between the capillary deformation and the wet sintering regimes of the Routh-Russel model, which provides strong confirmation of the model's validity. An inverse correlation between the model's dimensionless control parameter and the dimensionless drying time is discovered, which is useful for the design of fast-drying waterborne films.

  • Cooper BS, Gurney RS, Keddie JL, Siband E, Dupin D. (2014) 'Power density threshold for switching off the tack adhesion of colloidal nanocomposites'. Macromolecular Chemistry and Physics,

    Abstract

    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.

  • Udagama R, Bourgeat-Lami E, Mckenna TFL, Alarcón CDLH, Keddie JL, Tsavalas JG. (2014) 'Acrylic-alkyd hybrids: Secondary nucleation, particle morphology, and limiting conversions'. Macromolecular Reaction Engineering,

    Abstract

    The chemical incorporation of an unsaturated alkyd into an acrylic polymer created via miniemulsion polymerisation was studied. The variation of the number ratio of polymer particles to initial droplets with conversion, and changes in individual monomer conversions with increasing alkyd levels were the main quantities used to study the effect of increasing alkyd quantity in the hybrid system. Homogeneous nucleation was more significant in systems rich in the more hydrophilic methyl methacrylate (MMA). Changes in particle morphology with monomer conversion, as well as limited monomer conversion were observed. The results emphasize the importance of proper pairing of the miscibility between the specific acrylics and alkyds used in these hybrid polymers. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • Georgiadis A, Muhamad FN, Utgenannt A, Keddie JL. (2013) 'Aesthetically textured, hard latex coatings by fast IR-assisted evaporative lithography'. Progress in Organic Coatings, 76 (12), pp. 1786-1791.

    Abstract

    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.

  • Akram N, Ishaq M, Zuber M, Gurney RS, Keddie JL. (2013) 'Influence of Polyol Molecular Weight and Type on the Tack and Peel Properties of Waterborne Polyurethane Pressure-Sensitive Adhesives'. Macromolecular Reaction Engineering, 7 (10), pp. 493-503.

    Abstract

    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.

  • Mills CA, Al-Otaibi H, Intaniwet A, Shkunov M, Pani S, Keddie JL, Sellin PJ. (2013) 'Enhanced x-ray detection sensitivity in semiconducting polymer diodes containing metallic nanoparticles'. Journal of Physics D: Applied Physics, 46 (27) Article number 275102

    Abstract

    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.

  • Mills CA, Chan Y-F, Intaniwet A, Nisbet A, Keddie JL, Sellin PJ. (2013) 'Direct Detection of 6 MV X-rays from a Medical Linear Accelerator using a Semiconducting Polymer Diode'. Physics in Medicine and Biology, 58 (13), pp. 4471-4482.

    Abstract

    Recently, a new family of low-cost x-radiation detectors have been developed, based on semiconducting polymer diodes, which are easy to process, mechanically flexible, relatively inexpensive, and able to cover large areas. To test their potential for radiotherapy applications such as beam monitors or dosimeters, as an alternative to the use of solid-state inorganic detectors, we present the direct detection of 6 MV x-rays from a medical linear accelerator using a thick film, semiconducting polymer detector. The diode was subjected to 4 ms pulses of 6 MV x-rays at a rate of 60 Hz, and produces a linear increase in photocurrent with increasing dose rate (from 16.7 to 66.7 mGy s(−1)). The sensitivity of the diode was found to range from 13 to 20 nC mGy(−1) cm(−3), for operating voltages from −50 to −150 V, respectively. The diode response was found to be stable after exposure to doses up to 15 Gy. Testing beyond this dose range was not carried out. Theoretical calculations show that the addition of heavy metallic nanoparticles to polymer films, even at low volume fractions, increases the x-ray sensitivity of the polymer film/nanoparticle composite so that it exceeds that for silicon over a wide range of x-ray energies. The possibility of detecting x-rays with energies relevant to medical oncology applications opens up the potential for these polymer detectors to be used in detection and imaging applications using medical x-ray beams.

  • Utgenannt A, Muskens OL, Kanaras AG, Keddie JL. (2013) 'Directed organization of gold nanoparticles in polymer coatings through infrared-assisted evaporative lithography'. Chemical Communications, 49 (39), pp. 4253-4255.

    Abstract

    Infrared-assisted evaporative lithography (IRAEL) is presented as an emerging technology to direct the assembly of gold nanospheres (AuNSs) into large-scale superstructures within colloidal polymeric coatings. The organization of gold nanoparticle arrays within the superstructures can be tuned over length scales, ranging from micrometers up to several millimetres, giving rise to intrinsic plasmonic properties. © 2013 The Royal Society of Chemistry.

  • Gurney RS, Dupin D, Siband E, Ouzineb K, Keddie JL. (2013) 'Large-area patterning of the tackiness of a nanocomposite adhesive by sintering of nanoparticles under IR radiation.'. ACS Appl Mater Interfaces, United States: 5 (6), pp. 2137-2145.

    Abstract

    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.

  • Gonzalez E, Paulis M, Barandiaran MJ, Keddie JL. (2013) 'Use of a Routh-Russel deformation map to achieve film formation of a latex with a high glass transition temperature'. Langmuir, 29 (6), pp. 2044-2053.

    Abstract

    In the film formation of latex, particle deformation can occur by processes of wet sintering, dry sintering, or capillary action. When latex films dry nonuniformly and when particles deform and coalesce while the film is still wet, a detrimental skin layer will develop at the film surface. In their process model, Routh and Russel proposed that the operative particle deformation mechanism can be determined by the values of control parameters on a deformation map. Here, the film formation processes of three methyl methacrylate/butyl acrylate copolymer latexes with high glass transition temperatures (T ), ranging from 45 to 64 C, have been studied when heated by infrared radiation. Adjusting the infrared (IR) power density enables the film temperature, polymer viscosity, and evaporation rate during latex film formation to be controlled precisely. Different polymer particle deformation mechanisms have been demonstrated for the same latex under a variety of film formation process conditions. When the temperature is too high, a skin layer develops. On the other hand, when the temperature is too low, particles deform by dry sintering, and the process requires extended time periods. The deduced mechanisms can be interpreted and explained by the Routh-Russel deformation maps. Film formation of hard (high T) coatings is achieved without using coalescing aids that emit volatile organic compounds (VOCs), which is a significant technical achievement. © 2013 American Chemical Society.

  • Lopez A, Reyes Y, Asua JM, Lopez A, Degrandi-Contraires E, Creton C, Canetta E, Keddie JL, Canetta E. (2013) 'Simultaneous free-radical and addition miniemulsion polymerization: Effect of the chain transfer agent on the microstructure of polyurethane-acrylic pressure-sensitive adhesives'. Macromolecular Materials and Engineering, 298 (1), pp. 53-66.

    Abstract

    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.

  • Gurney RS, Dupin D, Nunes JS, Ouzineb K, Siband E, Asua JM, Armes SP, Keddie JL. (2012) 'Switching Off the Tackiness of a Nanocomposite Adhesive in 30 s via Infrared Sintering.'. ACS Appl Mater Interfaces, United States: 4 (10), pp. 5442-5452.

    Abstract

    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.

  • Jurewicz I, Keddie JL, Dalton AB. (2012) 'Importance of capillary forces in the assembly of carbon nanotubes in a polymer colloid lattice.'. Langmuir, United States: 28 (21), pp. 8266-8274.

    Abstract

    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.

  • Trueman RE, Lago Domingues E, Emmett SN, Murray MW, Keddie JL, Routh AF. (2012) 'Autostratification in drying colloidal dispersions: experimental investigations'. Langmuir, United States: 28 (7), pp. 3420-3428.

    Abstract

    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.

  • Irmukhametova GS, Fraser BJ, Keddie JL, Mun GA, Khutoryanskiy VV. (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'. LANGMUIR, 28 (1), pp. 299-306.

    Abstract

    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.

  • Goikoetxea M, Reyes Y, de las Heras Alarcón CM, Minari RJ, Beristain I, Paulis M, Barandiaran MJ, Keddie JL, Asua JM. (2012) 'Transformation of waterborne hybrid polymer particles into films: Morphology development and modeling'. Polymer, 53 (5), pp. 1098-1108.

    Abstract

    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.

  • Intaniwet A, Mills CA, Shkunov M, Sellin PJ, Keddie JL. (2012) 'Heavy metallic oxide nanoparticles for enhanced sensitivity in semiconducting polymer x-ray detectors'. Nanotechnology, 23 (23) Article number 235502

    Abstract

    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.

  • Georgiadis A, Routh AF, Murray MW, Keddie JL. (2011) 'Bespoke periodic topography in hard polymer films by infrared radiation-assisted evaporative lithography'. Soft Matter, 7 (23), pp. 11098-11102.
  • Intaniwet A, Keddie JL, Shkunov M, Sellin PJ. (2011) 'High charge-carrier mobilities in blends of poly(triarylamine) and TIPS-pentacene leading to better performing X-ray sensors'. Organic Electronics, 12 (11), pp. 1903-1908.

    Abstract

    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.

  • Jurewicz I, Worajittiphon P, King AA, Sellin PJ, Keddie JL, Dalton AB. (2011) 'Locking carbon nanotubes in confined lattice geometries--a route to low percolation in conducting composites.'. J Phys Chem B, United States: 115 (20), pp. 6395-6400.

    Abstract

    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.

  • Lopez A, Degrandi-Contraires E, Canetta E, Creton C, Keddie JL, Asua JM. (2011) 'Waterborne Polyurethane-Acrylic Hybrid Nanoparticles by Miniemulsion Polymerization: Applications in Pressure-Sensitive Adhesives'. LANGMUIR, 27 (7), pp. 3878-3888.
  • Georgiadis A, Bryant PA, Murray M, Beharrell P, Keddie JL. (2011) 'Resolving the Film-Formation Dilemma with Infrared Radiation-Assisted Sintering.'. Langmuir, 27 (6), pp. 2176-2180.

    Abstract

    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.

  • López García I, Keddie JL, Sferrazza M. (2011) 'Some insights into the structural relaxation of spin-cast, glassy polymer thin films'. Polymer Journal, 43 (2), pp. 214-217.

    Abstract

    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.

  • López García I, Keddie JL, Sferrazza M. (2011) 'Probing the early stages of solvent evaporation and relaxation in solvent-cast polymer thin films by spectroscopic ellipsometry'. Surface and Interface Analysis, 43 (11), pp. 1448-1452.

    Abstract

    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.

  • Lopez A, Degrandi E, Canetta E, Keddie JL, Creton C, Asua JM. (2011) 'Simultaneous free radical and addition miniemulsion polymerization: Effect of the diol on the microstructure of polyurethane-acrylic pressure-sensitive adhesives'. Polymer, 52 (14), pp. 3021-3030.
  • Worajittiphon P, Jurewicz I, King AAK, Keddie JL, Dalton AB. (2010) 'Enhanced Thermal Actuation in Thin Polymer Films Through Particle Nano-Squeezing by Carbon Nanotube Belts'. ADVANCED MATERIALS, 22 (46), pp. 5310-5314.
  • Liu D, Abdullah CAC, Sear RP, Keddie JL. (2010) 'Cell adhesion on nanopatterned fibronectin substrates'. SOFT MATTER, 6 (21), pp. 5408-5416.

    Abstract

    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.

  • Wang T, de las Heras Alarcon CD, Goikoetxea M, Beristain I, Paulis M, Barandiaran MS, Asua JM, Keddie JL. (2010) 'Cross-Linked Network Development in Compatibilized Alkyd/Acrylic Hybrid Latex Films for the Creation of Hard Coatings'. Langmuir: the ACS journal of surfaces and colloids, 26 (17), pp. 14323-14333.
  • Intaniwet A, Mills CA, Sellin PJ, Shkunov M, Keddie JL. (2010) 'Achieving a Stable Time Response in Polymeric Radiation Sensors under Charge Injection by X-rays'. 5th Edition. ACS APPL MATER INTER, 2 (6), pp. 1692-1699.

    Abstract

    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.

  • Jurewicz I, King AAK, Worajittiphon P, Asanithi P, Brunner EW, Sear RP, Hosea TJC, Keddie JL, Dalton AB. (2010) 'Colloid-Assisted Self-Assembly of Robust, Three-Dimensional Networks of Carbon Nanotubes over Large Areas'. MACROMOLECULAR RAPID COMMUNICATIONS, 31 (7), pp. 609-615.
  • Agirre A, Asua JM, Heras-Alarcón CDL, Wang T, Keddie JL. (2010) 'Waterborne, semicrystalline, pressure-sensitive adhesives with temperature-responsiveness and optimum properties'. ACS Applied Materials and Interfaces, 2 (2), pp. 443-451.

    Abstract

    The synthesis and resulting temperature-responsive properties of semicrystalline waterborne pressure-sensitive adhesives (PSAs) were investigated. A crystalline polymer fraction was produced in situ within waterborne particles by miniemulsion polymerization of non-branched long chain acrylates. The degree of crystallinity was controlled by copolymerization with a short chain acrylate. The polymerization strategy determined the polymer architecture and film structure, which then influenced the adhesion properties. The high sensitivity of the adhesion strength of these PSAs to temperature, in the range around the crystal melting point, opens up the possibility of designing temperature-responsive adhesives. With the right distribution and concentration of crystalline polymers, a simultaneous increase in both the peel strength and the shear resistance was obtained, which is a combination that is often not found when optimizing adhesive properties. © 2010 American Chemical Society.

  • Bushnak IA, Labeed FH, Sear RP, Keddie JL. (2010) 'Adhesion of microorganisms to bovine submaxillary mucin coatings: effect of coating deposition conditions'. BIOFOULING, 26 (4), pp. 387-397.

    Abstract

    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.

  • Agirre A, de las Heras-Alarcon C, Wang T, Keddie JL, Asua JM. (2010) 'Waterborne, Semicrystalline, Pressure-Sensitive Adhesives with Temperature-Responsiveness and Optimum Properties'. ACS APPLIED MATERIALS & INTERFACES, 2 (2), pp. 443-451.
  • Daar E, Kaabar W, Lei C, Keddie JL, Nisbet A, Bradley DA. (2010) 'AFM and uni-axial testing of pericardium exposed to radiotherapy doses'. Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 652 (1), pp. 874-877.
  • Intaniwet A, Mills CA, Shkunov M, Thiem H, Keddie JL, Sellin PJ. (2009) 'Characterization of thick film poly(triarylamine) semiconductor diodes for direct x-ray detection'. JOURNAL OF APPLIED PHYSICS, 106 (6) Article number ARTN 064513
  • Bradley M, Liu D, Keddie JL, Vincent B, Burnett G. (2009) 'The Uptake and Release of Cationic Surfactant from polyampholyte Microgel Particles in Dispersion and as an Adsorbed Monolayer'. LANGMUIR, 25 (17), pp. 9677-9683.
  • Liu D, Wang T, Keddie JL. (2009) 'Protein Nanopatterning on Self-Organized Poly(styrene-b-isoprene) Thin Film Templates'. LANGMUIR, 25 (8), pp. 4526-4534.

    Abstract

    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.

  • Wang T, Canetta E, Weerakkody TG, Keddie JL, Rivas U. (2009) 'pH dependence of the properties of waterborne pressure-sensitive adhesives containing acrylic acid.'. ACS Appl Mater Interfaces, United States: 1 (3), pp. 631-639.

    Abstract

    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.

  • Wang T, Keddie JL. (2009) 'Design and fabrication of colloidal polymer nanocomposites'. Advances in Colloid and Interface Science, 147-148, pp. 319-332.

    Abstract

    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.

  • Nikonenko NA, Bushnak IA, Keddie JL. (2009) 'Spectroscopic ellipsometry of mucin layers on an amphiphilic diblock copolymer surface'. Applied Spectroscopy, 63 (8), pp. 889-898.

    Abstract

    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.

  • Keddie JL. (2009) 'Mapping the route from wet to dry'. European Coatings Journal, (11), pp. 28-32.
  • Canetta E, Marchal J, Lei C-H, Deplace F, Koenig AM, Creton C, Ouzineb K, Keddie JL. (2009) 'A Comparison of Tackified, Miniemulsion Core-Shell Acrylic Latex Films with Corresponding Particle-Blend Films: Structure-Property Relationships'. LANGMUIR, 25 (18), pp. 11021-11031.
  • Wang T, Colver PJ, Bon SAF, Keddie JL. (2009) 'Soft polymer and nano-clay supracolloidal particles in adhesives: synergistic effects on mechanical properties'. SOFT MATTER, 5 (20), pp. 3842-3849.
  • Deplace F, Rabjohns MA, Yamaguchi T, Foster AB, Carelli C, Lei C-H, Ouzineb K, Keddie JL, Lovell PA, Creton C. (2009) 'Deformation and adhesion of a periodic soft-soft nanocomposite designed with structured polymer colloid particles'. SOFT MATTER, 5 (7), pp. 1440-1447.
  • Rodriguez R, Alarcon CDLH, Ekanayake P, McDonald PJ, Keddie JL, Barandiaran MJ, Asua JM. (2008) 'Correlation of Silicone Incorporation into Hybrid Acrylic Coatings with the Resulting Hydrophobic and Thermal Properties'. MACROMOLECULES, 41 (22), pp. 8537-8546.
  • Wang T, Dalton AB, Keddie JL. (2008) 'Importance of Molecular Friction in a Soft Polymer-Nanotube Nanocomposite'. MACROMOLECULES, 41 (20), pp. 7656-7661.
  • Kessel N, Illsley DR, Keddie JL. (2008) 'The diacetone acrylamide crosslinking reaction and its influence on the film formation of an acrylic latex'. JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Toronto, CANADA: 5 (3), pp. 285-297.
  • Koenig AM, Weerakkody TG, Keddie JL, Johannsmann D. (2008) 'Heterogeneous drying of colloidal polymer films: Dependence on added salt'. LANGMUIR, 24 (14), pp. 7580-7589.

    Abstract

    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.

  • Wang T, Lei C-H, Liu D, Manea M, Asua JM, Creton C, Dalton AB, Keddie JL. (2008) 'A molecular mechanism for toughening and strengthening waterborne nanocomposites'. ADVANCED MATERIALS, 20 (1), pp. 90-+.
  • Selvakumaran J, Keddie JL, Ewins DJ, Hughes MP. (2008) 'Protein adsorption on materials for recording sites on implantable microelectrodes'. JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 19 (1), pp. 143-151.
  • Gundabala VR, Lei C-H, Ouzineb K, Dupont O, Keddie JL, Routh AF. (2008) 'Lateral Surface Nonuniformities in Drying Latex Films'. AICHE JOURNAL, 54 (12), pp. 3092-3105.
  • Wang T, Liu D, Keddie JL. (2007) 'An alternative approach to the modification of talc for the fabrication of polypropylene/Talc composites'. JOURNAL OF APPLIED POLYMER SCIENCE, 106 (1), pp. 386-393.
  • Nerapusri V, Keddie JL, Vincent B, Bushnak LA. (2007) 'Absorption of cetylpyridinium chloride into Poly(N-isopropylacrylamide)-Based microgel particles, in dispersion and as surface-deposited monolayers'. 5th Edition. LANGMUIR, 23 (19), pp. 9572-9577.

    Abstract

    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.

  • Keddie JL, Ekanayake P, Koenig AM, Weerakkody TG, Barber N, Johannsmann D, Sear RP, McDonald PJ. (2007) 'Influence of the colloidal stability of latex particles on their distribution in drying films'. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 234
  • Keddie JL, Wang T, Jurewicz I, Dalton AB, Creton C, Manea M, Asua JM. (2007) 'Multifunctional nanocomposites of soft polymer colloids and carbon nanotubes'. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 234
  • Boroumand FA, Zhu M, Dalton AB, Keddie JL, Sellin PJ, Gutierrez JJ. (2007) 'Direct x-ray detection with conjugated polymer devices'. APPLIED PHYSICS LETTERS, 91 (3) Article number ARTN 033509
  • Wang T, Lei C-H, Dalton AB, Manea M, Asua JM, Keddie JL. (2007) 'COLL 306-Waterborne nanocomposite pressure-sensitive adhesives: Achieving enhanced adhesion combined with electrical conductivity'. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 233
  • Wang T, Lei C-H, Dalton AB, Manea M, Asua JM, Keddie JL. (2007) 'Waterborne nanocomposite pressure-sensitive adhesives: Achieving enhanced adhesion combined with electrical conductivity'. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 233
  • Lei C-H, Ouzineb K, Dupont O, Routh AF, Gundabala VR, Hinder SJ, Keddie JL. (2007) 'Lateral distribution of surfactants in waterborne pressure sensitive adhesive films: Theory and experiment'. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 233
  • Lei CH, Keddie JL, Ouzineb K, Dupont O. (2007) 'Probing particle structure in waterborne pressure-sensitive adhesives with atomic force microscopy'. Journal of Colloid and Interface Science, 307 (1), pp. 56-63.

    Abstract

    There is a need to know the nanostructure of pressure-sensitive adhesive (PSA) films obtained from waterborne polymer colloids so that it can be correlated with properties. Intermittent-contact atomic force microscopy (AFM) of an acrylic waterborne PSA film identifies two components, which can be attributed to the polymer and the solids in the serum (mainly surfactant). It is found that when the average AFM tapping force, F, is relatively low, the polymer particles appear to be concave. But when F is higher, the particles appear to have a convex shape. This observation is explained by a height artefact caused by differences in the indentation depths into the two components that vary with the tapping amplitude and F. To achieve the maximum contrast between the polymer and serum components, F should be set such that the indentation depths are as different as possible. Unlike what is found for the height images, the phase contrast images of the PSA do not show a reversal in contrast over the range of tapping conditions applied. The phase images are thus reliable in distinguishing the two components of the PSA according to their viscoelastic properties. At the surface of films dried at room temperature, the serum component is found in localized regions within permanent depression into the film. © 2006 Elsevier Inc. All rights reserved.

  • Adikaari AADT, Carey JD, Stolojan V, Keddie JL, Silva SRP. (2006) 'Bandgap enhancement of layered nanocrystalline silicon from excimer laser crystallization'. NANOTECHNOLOGY, 17 (21), pp. 5412-5416.
  • Nerapusri V, Keddie JL, Vincent B, Bushnak IA. (2006) 'Swelling and deswelling of adsorbed microgel monolayers triggered by changes in temperature, pH, and electrolyte concentration'. LANGMUIR, 22 (11), pp. 5036-5041.
  • Mallegol J, Bennett G, McDonald PJ, Keddie JL, Dupont O. (2006) 'Skin development during the film formation of waterborne acrylic pressure-sensitive adhesives containing tackifying resin'. J ADHESION, 82 (3), pp. 217-238.
  • Wang T, Lei C-H, Dalton AB, Keddie JL, Creton C, Lin Y, Fernando KAS, Sun Y-P, Manea M, Asua JM. (2006) 'Waterborne, nanocomposite pressure-sensitive adhesives with high tack energy, optical transparency, and electrical conductivity'. Advanced Materials, 18 (20), pp. 2730-2734.

    Abstract

    The waterborne, nanocomposite pressure-sensitive adhesives (PSA) with high tack energy, optical transparency, and electrical conductivity was studied. Pressure-sensitive adhesives adhere instantly and firmly to nearly any surface under the application of light pressure, without covalent bonding and activation. The debonding of PSAs occurs by a cavitation process followed by cavity expansion to create fibrils that extend in traction and contribute to the energy of adhesion. The surfactants and water-soluble polymers in latex films are known to decrease adhesive performance. It has been recognized that the interfaces in polymer/ carbon nanotubes (CNT) nanocomposites can have an influence on the viscoelastic property of the PSAs. Electrical conductivity in PSAs is conventionallky achieved through the use of metallic fillers in the form of flakes and particles.

  • Vandervorst P, Lei C-H, Lin Y, Dupont O, Dalton AB, Sun Y-P, Keddie JL. (2006) 'The fine dispersion of functionalized carbon nanotubes in acrylic latex coatings'. Progress in Organic Coatings, 57 (2), pp. 91-97.

    Abstract

    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.

  • Duckworth P, Richardson H, Carelli C, Keddie JL. (2005) 'Infrared ellipsometry of interdiffusion in thin films of miscible polymers'. Surface and Interface Analysis, 37 (1), pp. 33-41.

    Abstract

    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.

  • Keddie JL, Lopez-Garcia I, Richardson H, Sferrazza M. (2004) 'Thickness dependence of structural relaxation in spin-cast, glassy polymer thin films'. Physical Review E, 70 Article number 051805

    Abstract

    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.

  • Simpson TRE, Tabatabaian Z, Jeynes C, Parbhoo B, Keddie JL. (2004) 'Influence of interfaces on the rates of crosslinking in poly(dimethyl siloxane) coatings'. JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY, 42 (6), pp. 1421-1431.
  • Keddie JL, McDonald PJ, Gorce J-P, Mallégol J. (2004) 'Understanding water-borne coatings: New techniques to answer old questions'. Surface Coatings International Part A: Coatings Journal, 87 (2), pp. 70-73.
  • Lincoln BJ, Simpson TRE, Keddie JL. (2004) 'Water vapour sorption by the pedal mucus trail of a land snail'. Colloids and Surfaces B: Biointerfaces, 33 (3-4), pp. 251-258.
  • Richardson H, Sferrazza M, Keddie JL. (2003) 'Influence of the glass transition on solvent loss from spin-cast glassy polymer thin films.'. Eur Phys J E Soft Matter, France: 12 Suppl 1, pp. S87-S91.

    Abstract

    The interdependence of solvent loss and vitrification in spin-cast poly(methyl methacrylate) thin films is explored. Fast measurements of decreases in film thickness, achieved with ellipsometry, indicate that the rate of solvent (toluene) loss decreases sharply when the solvent volume fraction phi(solv) falls below about 0.15 and the film vitrifies. Ellipsometry and microgravimetry show that solvent is lost from a glassy thin film (150 nm thick) over of a period of more than ten hours, which is much longer than would be required if it was limited by diffusion in the glass. These results support the recently-proposed idea that the compression of the glass creates an energy barrier that slows down solvent loss.

  • Richardson H, Carelli C, Keddie JL, Sferrazza M. (2003) 'Structural relaxation of spin-cast glassy polymer thin films as a possible factor in dewetting.'. Eur Phys J E Soft Matter, France: 12 (3), pp. 437-440.

    Abstract

    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.

  • Aramendia E, Mallegol J, Jeynes C, Barandiaran MJ, Keddie JL, Asua JM. (2003) 'Distribution of surfactants near acrylic latex film surfaces: A comparison of conventional and reactive surfactants (surfmers)'. LANGMUIR, 19 (8), pp. 3212-3221.
  • Bennett G, Gorce JP, Keddie JL, McDonald PJ, Berglind H. (2003) 'Magnetic resonance profiling studies of the drying of film-forming aqueous dispersions and glue layers.'. Magn Reson Imaging, United States: 21 (3-4), pp. 235-241.

    Abstract

    We report magnetic resonance profiling experiments to monitor (i) the drying of alkyd emulsion layers, (ii) the cure of wood glue layers and (iii) water transport through glue lines. The alkyd drying is a two stage process. We report new results which support previous evidence that the alkyd drops do not coalesce until the water fraction is below circa 0.02. The profiles recorded from glue layers suggest that MR is a sensitive probe of the curing process and barrier properties of the glue. The measurements were made using GARField (stray field, STRAFI like) magnetic resonance profiling and an improved GARField magnet design characterized by two values of the gradient-to-field strength ratio at two locations offering the same field strength is also reported.

  • Simpson TRE, Keddie JL, Parbhoo B. (2003) 'The dependence of the rate of crosslinking in poly(dimethyl siloxane) on the thickness of coatings'. Polymer, 44 (17), pp. 4829-4838.

    Abstract

    We consider reasons why the crosslinking reaction rate in poly(dimethyl siloxane) (PDMS) network coatings might differ from the rate found in the bulk and specifically examine the influence of coating thickness. Infrared spectroscopic ellipsometry (IRSE) is employed as an in situ probe of the reactions between vinyl (-CH=CH) end groups on PDMS and SiH groups in a crosslinker and between unreacted SiH groups and hydroxyl/silanol groups within PDMS coatings, all on silicon substrates. Measurements of the concentrations of SiH groups (using the characteristic vibration at 2160 cm) were obtained from coatings between 1 and 27 μm in thickness, over temperatures ranging from 25 to 120 °C. First-order kinetics are exhibited in the consumption of SiH groups. The reaction rate constant is found to decrease with increasing coating thickness. Although there is evidence that the Pt catalyst segregates to the interface with the substrate, this phenomenon does not appear to have an impact on the thickness dependence. The diffusion of water into the silicone might be the rate-limiting step in the reactions, however, and therefore lead to the observed thickness dependence of the reaction rate. © 2003 Elsevier Science Ltd. All rights reserved.

  • Richardson H, Sferrazza M, Keddie JL. (2003) 'Influence of the glass transition on solvent loss from spin-cast glassy polymer thin films'. European Physical Journal E, 12 (SUPPL. 1), pp. 75-79.

    Abstract

    The interdependence of solvent loss and vitrification in spin-cast poly(methyl methacrylate) thin films is explored. Fast measurements of decreases in film thickness, achieved with ellipsometry, indicate that the rate of solvent (toluene) loss decreases sharply when the solvent volume fraction φ falls below about 0.15 and the film vitrifies. Ellipsometry and microgravimetry show that solvent is lost from a glassy thin film (150 nm thick) over of a period of more than ten hours, which is much longer than would be required if it was limited by diffusion in the glass. These results support the recently-proposed idea that the compression of the glass creates an energy barrier that slows down solvent loss. © EDP Sciences / Società Italiana di Fisica / Springer-Verlag 2003.

  • Simpson TRE, Keddie JL. (2003) 'Evidence from infrared ellipsometry for covalent bonding at a polymer/polymer interface with relevance to "lock-up" in pressure-sensitive adhesive laminates'. Journal of Adhesion, 79 (12), pp. 1207-1218.
  • Richardson H, Sferrazza M, Keddie JL. (2003) 'Slow relaxation of spin-cast poly(methyl methacrylate) confined in thin films'. Materials Research Society Symposium - Proceedings, 790, pp. 251-256.
  • Mallegol J, Dupont O, Keddie JL. (2003) 'Morphology and elasticity of waterborne acrylic pressure-sensitive adhesives investigated, with atomic force microscopy'. JOURNAL OF ADHESION SCIENCE AND TECHNOLOGY, 17 (2), pp. 243-259.

    Abstract

    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.

  • Mallegol J, Barry AM, Ciampi E, Glover PM, McDonald PJ, Keddie JL, Wallin M, Motiejauskaite A, Weissenborn PK. (2002) 'Influence of drier combination on through-drying in waterborne alkyd emulsion coatings observed with magnetic resonance profiling'. JOURNAL OF COATINGS TECHNOLOGY, 74 (933), pp. 113-124.
  • Gorce JP, Bovey D, McDonald PJ, Palasz P, Taylor D, Keddie JL. (2002) 'Vertical water distribution during the drying of polymer films cast from aqueous emulsions.'. Eur Phys J E Soft Matter, France: 8 (4), pp. 421-429.

    Abstract

    We present a systematic study of the vertical uniformity of water distribution during the drying of waterborne colloidal films, testing the predictions of a Peclet number Pe defined for this system. Pe indicates the relative contributions of water evaporation and Brownian diffusion in determining the concentration profile in the vertical direction ( i.e. normal to the substrate). When Pe < 1, the water concentration in films cast from an alkyd emulsion is found via magnetic-resonance profiling to be uniform with depth, which is consistent with expectations. When Pe > 1, a gradient in the water concentration develops, with less water near the interface with air. The water profiles reveal that the alkyd particles do not coalesce immediately upon contact in close-packing. At later times, a concentrated surface layer develops, but particles are not coalesced in this layer to form a continuous "skin", but rather the structure is likely to be that of a biliquid foam.

  • Mallegol J, Gorce JP, Dupont O, Jeynes C, McDonald PJ, Keddie JL. (2002) 'Origins and effects of a surfactant excess near the surface of waterborne acrylic pressure-sensitive adhesives'. LANGMUIR, 18 (11), pp. 4478-4487.
  • Zhao Y, Carey JD, Knoops N, Maetens D, Hopkinson I, Hay JN, Keddie JL. (2002) 'Inhibition of the surface levelling of thermosetting polyester powder coatings caused by surface tension gradients'. Journal of Materials Science, 37 (22), pp. 4759-4768.

    Abstract

    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.

  • Mallegol J, Keddie JL, Dupont O. (2001) 'New insights into the imaging of waterborne acrylic pressure-sensitive adhesives by tapping mode AFM.'. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 222, pp. U346-U346.
  • Keddie JL, Gorce JP, Mallegol J, Wallin M, Barry AM, Ciampi E, Motiejauskaite A, Glover PM, McDonald PJ, Weissenborn PK. (2001) 'MR profiling of film formation and crosslinking in waterborne alkyd emulsions and emulsion paints.'. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 222, pp. U378-U378.
  • Salamanca JM, Ciampi E, Faux DA, Glover PM, McDonald PJ, Routh AF, Peters ACIA, Satguru R, Keddie JL. (2001) 'Lateral drying in thick films of waterborne colloidal particles'. LANGMUIR, 17 (11), pp. 3202-3207.
  • Sackin R, Ciampi E, Godward J, Keddie JL, McDonald PJ. (2001) 'Fickian ingress of binary solvent mixtures into glassy polymer'. MACROMOLECULES, 34 (4), pp. 890-895.
  • Keddie JL. (2001) 'Structural analysis of organic interfacial layers by ellipsometry'. Current Opinion in Colloid and Interface Science, 6 (2), pp. 102-110.

    Abstract

    Ellipsometry has 'come of age' as a technique for the analysis of problems related to colloid and interface science. It has advanced far beyond applications of measuring film thickness or optical constants - although these remain important uses. Studies of the structure of polymers at the solid/liquid interface have been advanced significantly by the realisation of Fourier transform ellipsometry. Another important achievement has been the calibrated measurement of the dynamic surface excess at the flowing surface of a liquid jet. The users of ellipsometry to study critical adsorption in binary liquids and to measure the width of liquid/liquid interfaces are also noteworthy. An important development is the use of infrared - rather than visible - light, which opens up numerous possibilities for the simultaneous structural and chemical interrogation of interfaces non-invasively. © 2001 Elsevier Science Ltd. All rights reserved.

  • Mallégol J, Dupont O, Keddie JL. (2001) 'Obtaining and interpreting images of waterborne acrylic pressure-sensitive adhesives by tapping-mode atomic force microscopy'. Langmuir, 17 (22), pp. 7022-7031.

    Abstract

    The first atomic force microscopy (AFM) images of waterborne acrylic pressure-sensitive adhesives (PSAs) are presented along with details of their optimum scanning conditions. Driving this work is a huge practical need for information about the surface morphology of waterborne PSAs, which are deposited from colloidal dispersions to yield highly tacky, soft surfaces. These surfaces present contradictory requirements for tapping-mode AFM. Whereas soft surfaces require light tapping to avoid surface damage, tacky surfaces require energetic tapping to enable the tip to lift off of the surface. We have made a systematic study of the effects of several key parameters: the cantilever spring constant; the free amplitude of oscillation (A); the setpoint value (d); and the setpoint ratio (r = d/A), which we have re-defined for a soft surface to account for the indentation depth. Amplitude-distance curves were obtained from the PSA surfaces to evaluate the tip's indentation depth. Reliable images are obtained when these parameters are known and optimized. While the "true" surface of the film is actually rather smooth, images of the sub-surface particle morphology are best obtained with a stiff cantilever (spring constant of 48 N/m) and a large A (about 135 nm). Setting r close to unity minimizes the indentation of the tip and the resultant surface deformation.

  • Holl Y, Keddie JL, McDonald PJ, Winnik WA. (2001) 'Drying modes of polymer colloids'. ACS Symposium Series, 790, pp. 2-26.

    Abstract

    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.

  • Andrei DC, Keddie JL, Hay JN, Yeates SG, Briscoe BJ, Parsonage D. (2001) 'Nano-mechanical properties and topography of thermosetting acrylic powder coatings'. JOURNAL OF COATINGS TECHNOLOGY, 73 (912), pp. 65-73.
  • Mallégol J, Keddie JL, Dupont O. (2001) 'Etude structurale des films d'adhesifs acryliques sensibles a la pression par microscopie a force atomique en mode tapping'. Vide: Science, Technique et Applications, (302 SUPPL.), pp. 34-37.
  • Tzitzinou A, Keddie JL, Geurts JL, Mulder M, Satguru R, Treacher KE. (2001) 'Molecular weight effects on the film formation of latex and on surfactant distribution and morphology'. ACS Symposium Series, 790, pp. 58-87.

    Abstract

    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 (M = 705, 000 Daltons) up to 30°C above MFT. In contrast, the lowest MW latex (M = 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.

  • Keddie J, Mallégol J, Dupont O. (2001) 'The technological and environmental pressures on advanced adhesives'. Materials World, 9 (11), pp. 22-24.

    Abstract

    The pressure-sensitive adhesive (PSA) industry is facing ongoing challenges to further develop its technologies and environmental performance. However, it's evident that the materials scientists' response to these challenges is leading to the development of products that are better for the environment and for human health. This paper looks at how PSAs are responding to environmental and technological challenges, and their increased use in high-performance applications.

  • Malucelli G, Sangermano M, Bongiovanni R, Priola A, Keddie JL. (2000) 'Water sorption in polymer network films synthesised from PEO oligomers containing acrylic and vinyl ether functionalities'. POLYMER BULLETIN, 45 (4-5), pp. 431-438.
  • Wallin M, Glover PM, Hellgren AC, Keddie JL, McDonald PJ. (2000) 'Depth profiles of polymer mobility during the film formation of a latex dispersion undergoing photoinitiated cross-linking'. MACROMOLECULES, 33 (22), pp. 8443-8452.
  • Ciampi E, Goerke U, Keddie JL, McDonald PJ. (2000) 'Lateral transport of water during drying of alkyd emulsions'. LANGMUIR, 16 (3), pp. 1057-1065.
  • McMurtry S, Wright JD, Jackson DA, Keddie JL. (2000) 'Humidity sensing using PMMA-PMTGA-PMMA polymer in low coherence interferometric system'. ELECTRONICS LETTERS, 36 (1), pp. 73-74.
  • Tzitzinou A, Keddie JL, Geurts JM, Peters ACIA, Satguru R. (2000) 'Film formation of latex blends with bimodal particle size distributions: Consideration of particle deformability and continuity of the dispersed phase'. Macromolecules, 33 (7), pp. 2695-2708.

    Abstract

    The film formation of dispersions with bimodal particle size distribution and with varying concentrations of the two particle sizes are studied. The formation of deformable blends with soft particles is compared with those of deformable blends with nondeformable particles. Ellipsometry is used to acquire data for studying film morphology.

  • Gilchrist VA, Lu JR, Keddie JL, Staples E, Garrett P. (2000) 'Adsorption of penta(ethylene glycol) monododecyl ether at the solid poly(methyl methacrylate)-water interface: A spectroscopic ellipsometry study'. Langmuir, 16 (2), pp. 740-748.

    Abstract

    We have examined the adsorption of a nonionic surfactant, penta(ethylene glycol) monododecyl ether (CE), at the poly(methyl methacrylate) (PMMA)-water interface using spectroscopic ellipsometry. The solid PMMA surface was deposited by spin casting an ultrathin film onto a freshly cleaned silicon wafer. Measurements by both spectroscopic ellipsometry (SE) and atomic force microscopy (AFM) showed that the thin PMMA film was uniform with no prominent structural features on the surface. The adsorption of CE at the solid PMMA-aqueous solution interface was studied using a specially designed cell with a fixed angle of incidence of 75°, and the measurements were made over a wide concentration range around the critical micellar concentration (cmc). It was found that the adsorption is completely reversible and that there is no observable penetration of CE into the PMMA. The adsorption was found to reach equilibrium well within seconds. Although spectroscopic ellipsometry cannot allow a reliable measurement of layer thickness as a result of coupling between refractive indices and layer thickness for ultrathin layers, the surface excess at a given concentration can be determined reliably. The limiting area per molecule at the cmc was calculated to be 50±3 angstroms, in good agreement with the value obtained from a previous neutron reflection study.

  • Parbhoo B, Izraej S, Salamanca JM, Keddie JL. (2000) 'Use of ellipsometry and gravimetry to develop calibration standards for measuring silicone coat weight and thickness with x-ray fluorescence spectroscopy'. Surface and Interface Analysis, 29 (5), pp. 341-345.

    Abstract

    There are important technological and scientific needs for accurate and precise measurements of the weight and thickness of silicone coatings, which are used in wide-ranging applications. X-ray fluorescence (XRF) spectroscopy offers one means of achieving such measurements. Here we show that, as predicted from theory, the intensity of the XRF intensity is linearly proportional to the thickness and weight of a relatively thin silicone coating on a poly (carbonate) substrate. This linear relationship is demonstrated using both gravimetry and spectroscopic ellipsometry to provide two independent measurements of coating thickness, resulting in a robust method for the calibration of the XRF intensity. Copyright © 2000 John Wiley & Sons, Ltd.

  • Styrkas DA, Lu JR, Keddie JL, Bütün V, Armes SP. (2000) 'pH-controlled adsorption of polyelectrolyte diblock copolymers at the solid/liquid interface'. Langmuir, 16 (14), pp. 5980-5986.

    Abstract

    We investigated the pH dependence of the adsorption of polyelectrolyte diblock copolymers from aqueous solution onto the native oxide surface of silicon using spectroscopic ellipsometry. The observed adsorption behavior is closely related to the chemical structure and the hydrophilic-hydrophobic balance of the copolymers. These amphiphilic copolymers contain hydrophobic residues comprising either 2-(diethylamino)ethyl methacrylate (DEA) or 2-(diisopropylamino)ethyl methacrylate (DPA). The copolymers also contain hydrophilic residues that are either (1) methyl-quaternized or benzyl-quaternized 2-(dimethylamino)ethyl methacrylate (designated Me-DMA or Bz-DMA, respectively) or (2) sulfopropyl betainized 2-(dimethylamino)ethyl methacrylate (Bet-DMA). The DEA and DPA residues can be tuned to become hydrophilic by adjusting the solution pH. Thus, these diblock copolymers can be molecularly dissolved in acidic media without using cosolvents as a result of the protonation of the tertiary amine groups. At low solution pH, adsorption of the copolymers is only about 0.5-1.5 mg/m, which is expected for polyelectrolyte adsorption. Above a pH of 7, there is a pronounced increase in the adsorbed amount. This change in adsorption coincides with the formation of copolymer micelles in the bulk solution. Hence, it is likely that the interfacial layer consists of adsorbed micelles. In the Bz-DMA-b-DEA copolymer, only a small fraction of DEA blocks (22%) is needed to achieve a relatively large increase in the adsorption at higher pH. On the other hand, control experiments confirm that the corresponding homopolymers show no sharp change in the extent of adsorption with pH. Changing the hydrophobic residues from DEA to DPA does not significantly affect the extent of adsorption. However, substitution of the hydrophilic Bz-DMA residues with Bet-DMA significantly increases the extent of adsorption at higher pH. This is probably because the electrically neutral betainized block is less hydrophilic than the cationic Bz-DMA block. This work provides insight into the major influences on the block copolymer adsorption and thus creates a framework for tuning adsorption behavior.

  • Andrei DC, Hay JN, Keddie JL, Sear RP, Yeates SG. (2000) 'Surface levelling of thermosetting powder coatings: theory and experiment'. Journal of Physics D: Applied Physics, 33 (16), pp. 1975-1981.

    Abstract

    The deposition of protective coatings from thermosetting polymer powders is an ecological, economic and energy-efficient technology. A frequent problem encountered with powder coatings is a rough surface (with undulations on a length scale much greater than the powder particle size) that detracts from the visual appearance. The levelling (i.e. flattening) of the surface of a polymer melt is driven by the minimization of the surface energy but opposed by the (possibly time-dependent) viscosity of the melt. We address the problem by developing a model of surface levelling to consider flow in two directions, building upon a one-dimensional model already in the literature. We have performed simulations to predict the final coating profiles starting with a Gaussian profile and using experimentally determined values of polymer viscosity. To compare to the simulations, we have measured experimentally the dimensions of surface undulations on coatings formed from thermosetting acrylic powder layers having purposely created features of known dimensions. There is good agreement between simulation and experiment. Both find that the levelling proceeds to a greater extent with increasing coating thickness and with decreasing lateral dimension of the surface undulation. Our results open up the possibility of predicting final surface topography given the rheological properties of a polymer.

  • Keddie JL, Andrei DC, Sear RPL, Yeates SG. (1999) 'Surface flattening of thermosetting powder coatings: Theory and experiment.'. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 218, pp. U626-U626.
  • Keddie JL, Ciampi E, McDonald PJ, Salamanca JM. (1999) 'Magnetic resonance imaging of the film formation of waterborne coatings.'. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 218, pp. U621-U621.
  • Tzitzinou A, Keddie JL, Jeynes C, Mulder M, Geurts J, Treacher KE, Satguru R, Zhdan P. (1999) 'Molecular weight effects on film formation of latex and surfactant morphology.'. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 218, pp. U609-U609.
  • Murphy EF, Keddie JL, Lu JR, Brewer J, Russell J. (1999) 'The reduced adsorption of lysozyme at the phosphorylcholine incorporated polymer/aqueous solution interface studied by spectroscopic ellipsometry.'. Biomaterials, ENGLAND: 20 (16), pp. 1501-1511.

    Abstract

    Coating hydrogel polymers onto solid substrates can reduce the adsorption of proteins onto these surfaces, but the extent of the reduction in protein adsorption is strongly dependent on how the surface layer is coated. We have examined the effect of coating conditions on the structure of thin polymer films formed from a number of poly(methacrylate)-based hydrogel polymers via the dip-coating method. We show in this work how the polarity of the solvent, the speed of lifting, and the annealing temperature affect the thickness and uniformity of ultrathin phosphorylcholine (PC)-incorporated polymer films coated on the surface of native oxide on silicon and the subsequent interaction of these coated surfaces with lysozyme molecules. Our results show that the uniformity of the polymer film, and thus the smoothness of the outer film surface, influence the extent of reduction in protein adsorption. We suggest that the reduction in lysozyme adsorption is the result of a layer of PC groups on the surface of the polymer film. The improvement of the smoothness of the film results in the formation of a close-packed PC layer on the outer surface of the polymer film, leaving few defects or cavities on which protein molecules can bind.

  • McDonald PJ, Ciampi E, Keddie JL, Heidenreich M, Kimmich R. (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'. Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, 59 (1), pp. 874-884.

    Abstract

    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.

  • Bero MA, Gilboy WB, Glover PM, Keddie JL. (1999) 'Three-dimensional radiation dose measurements with Ferrous Benzoic Acid Xylenol Orange in Gelatin gel and optical absorption tomography'. Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 422 (1-3), pp. 617-620.

    Abstract

    The optical characteristics of a Ferrous Benzoic Acid Xylenol Orange in Gelatin (FBXG) gel have been studied over the wavelength range 300-700 nm as a function of radiation dose. The unirradiated gel exhibits a strong absorption peak at 440 nm; with increasing dose this peak starts to reduce in intensity while a new broad peak centred at 585 nm begins to appear. Using Co gamma rays the absorption coefficients for these two peaks were found to vary linearly with dose up to at least 30Gy with slopes of -0.028cm Gy (440nm) and 0.069cm Gy (585nm). The pre- and post-irradiation stability was studied and absorbance changes of less than 1% per hour were observed over periods of a few days. The NMR response of FBXG gels was found to be marginally reduced compared to the standard Fricke dosemeter in gel form and the NMR technique is much less sensitive than the optical readout method. Tissue equivalent phantoms with dimensions of several centimetres can be constructed of FBXG gel and Optical Absorption Tomography (OAT) used to measure the three-dimensional dose distribution within them after exposure to radiation beams. The OAT technique is a much simpler and cheaper method of readout compared with Magnetic Resonance Imaging (MRI). © 1999 Elsevier Science B.V. All rights reserved.

  • Cappellani A, Keddie JL, Barradas NP, Jackson SM. (1999) 'Processing and characterization of sol-gel deposited TaO and TiO-TaO dielectric thin films'. Solid-State Electronics, 43 (6), pp. 1095-1099.

    Abstract

    High-dielectric thin films of Ti-doped TaO were deposited on n-type silicon substrate using the spin-on sol-gel process. Doping levels of 8 and 46 TiO mol% were used. Following deposition, films were processed at temperatures between 600 and 900 °C using rapid thermal annealing in NO. Spectroscopic ellipsometry (SE) and Rutherford backscattering spectrometry (RBS) were used to determine the thickness and the composition of the thin films and the interfacial reaction layers. Metal insulator-semiconductor capacitor structures were fabricated and impedance-frequency measurements were carried out to measure the dielectric constant of the deposited films. Results from both RBS and SE showed that a SiO layer is formed at the TaO/Si interface during processing, but the titanium doping inhibits the kinetics of its formation. We found that the dielectric constant of the highly Ti-doped TaO film was 78% greater than that of TaO sol-gel film processed under similar conditions.

  • Barradas NP, Keddie JL, Sackin R. (1999) 'Bayesian inference analysis of ellipsometry data'. Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, 59 (5), pp. 6138-6151.

    Abstract

    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.

  • Tzitzinou A, Jenneson PM, Clough AS, Keddie JL, Lu JR, Zhdan P, Treacher KE, Satguru R. (1999) 'Surfactant concentration and morphology at the surfaces of acrylic latex films'. Progress in Organic Coatings, 35 (1-4), pp. 89-99.

    Abstract

    The final outcome of surfactants during latex film formation is a topic of ongoing concern and interest. In this study of an acrylic latex containing an anionic surfactant, two notable phenomena are observed. (1) A higher surfactant concentration is present at the air surface of the latex films, regardless of the film-forming temperature and time. In some cases, surfactant is not visible in an atomic force microscope (AFM) image as a separate phase, but compositional profiles obtained with Rutherford backscattering spectrometry (RBS) reveal an enhanced concentration of surfactant over a depth from the surface that is comparable to the latex particle diameter. (2) The surfactant features that are imaged with the AFM evolve from a thin uniform layer, to a 'finger-like' morphology, to small flat droplets, and finally to larger, hemispherical 'blobs'. We suggest that surfactant is first deposited from the air/water interface onto the latex surface during the drying process. During this progression in the morphology of the surfactant, the ratio of the surface area-to-volume decreases. We speculate that this phenomenon is driven by a reduction in surface energy.

  • Styrkas DA, Keddie JL, Lu JR, Su TJ, Zhdan PA. (1999) 'Structure of self-assembled layers on silicon: Combined use of spectroscopic variable angle ellipsometry, neutron reflection, and atomic force microscopy'. Journal of Applied Physics, 85 (2), pp. 868-875.

    Abstract

    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.

  • Chen W-L, Shull KR, Papatheodorou T, Styrkas DA, Keddie JL. (1999) 'Equilibrium swelling of hydrophilic polyacrylates in humid environments'. Macromolecules, 32 (1), pp. 136-144.

    Abstract

    The hydrophilicity of polymers, as indicated by their swelling characteristics in water, is an important parameter with regard to their use as coatings which are able to modify the wettability and adhesive properties of a material. We have investigated the swelling behavior of a series of hydrophilic random copolymer coatings in controlled humidity environments and in water. Swelling data were obtained from a quartz crystal microbalance (QCM) and from spectroscopic ellipsometry. The hydrophilic polymers are based on polyacrylates with low molecular weight side chains of poly(ethylene glycol) (PEG). These polymers also contain a random distribution of acrylic acid. Triblock copolymers with these random copolymers as the midblock and poly(methyl methacrylate) (PMMA) as the end blocks have also been investigated. At low and intermediate humidities, the swelling behavior of appropriately chosen block copolymers is similar to the swelling behavior of the corresponding polymers that do not have the PMMA end blocks. Substantial differences between the two types of polymers are observed at very high humidities and in water. The PMMA end blocks stabilize the structure of the copolymer layer so that it does not dissolve in water. Swelling curves obtained from the quartz crystal microbalance and from ellipsometry are in agreement with one another when the shape of the quartz crystal resonance (as determined by impedance spectroscopy) is not affected by humidity. We also find evidence for a reversible, humidity-induced phase transition which is readily detectable by the quartz crystal microbalance. © 1999 American Chemical Society.

  • Newling B, Glover PM, Keddie JL, Lane DM, McDonald PJ. (1997) 'Concentration profiles in creaming oil-in-water emulsion layers determined with stray field magnetic resonance imaging'. Langmuir, 13 (14), pp. 3621-3626.

    Abstract

    We report the first use of stray field magnetic resonance imaging in the determination of concentration profiles in layers (with submillimeter thickness) of coarse oil-in-water emulsions that are undergoing creaming. We compare our results for emulsions having various oil contents to the predictions of a numerical model. In emulsions having low oil content (12 and 23 vol %), we find that the model adequately predicts the profile shape and time-dependent change in the lower region of the emulsion. In the cream layer at the top of each of the samples, however, the predictions of the model deviate substantially from the observed profiles. Whereas the model assumes that the concentration of oil in the cream layer is constant as the layer increases in thickness, we observe that there is a concentration gradient in the cream layer and that the concentration of oil in the layer increases with time. In explaining our findings, we consider the effects of polydispersity and the presence of gum xanthan in the continuous phase and also the possibility of gradual compaction of oil droplets in the cream layer (a phenomenon not considered in the model).

  • Clough AS, Jenneson PM, Keddie JL. (1997) 'Ion beam analysis of small molecule diffusion in polymers'. Annual Technical Conference - ANTEC, Conference Proceedings, 2, pp. 2211-2215.

    Abstract

    Ion beam analysis has been applied to a variety of problems involving the diffusion of small molecules in polymeric matrices. Energy loss techniques have been used to study the diffusivity of dye molecules and water. Beam traversing techniques have determined water concentrations in hydrophilic polymers over distances of several mm. The suite of techniques available allows the analysis of nearly every element.

  • Jenneson PM, Clough AS, Keddie JL, Lu JR, Meredith P. (1997) 'Non-ionic surfactant concentration profiles in undamaged and damaged hair fibres determined by scanning ion beam nuclear reaction analysis'. Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 132 (4), pp. 697-703.

    Abstract

    Nuclear Reaction Analysis (NRA) was used with a scanning MeV He ion microbeam to determine the extent of permeation and segregation of a deuterated non-ionic surfactant (dCE) into virgin (undamaged) and alkalinic perm damaged hair fibres. 2-D concentration maps show an accumulation of deuterated surfactant in the cortex and medulla of both the virgin and damaged hair. By normalising to the matrix carbon, surfactant levels in the damaged hair were found to be three times higher than in the undamaged hair. This is the first reported direct spatial evidence of the penetration of surfactant into the centre of hair fibres. Furthermore it is the first application of NRA to this type of complex biological matrix. © 1997 Elsevier Science B.V.

  • Keddie JL. (1997) 'Film formation of latex'. Materials Science and Engineering R: Reports, 21 (3), pp. 101-170.

    Abstract

    Latex film formation, the process by which an aqueous dispersion of polymer particles is transformed into a continuous material, has a direct bearing on the final film morphology and properties. Each of the primary stages of film formation (evaporative drying and ordering; particle deformation; and polymer interdiffusion) have been studied experimentally. Recently-developed non-invasive techniques, including direct nonradiative energy transfer, atomic force microscopy, small angle neutron scattering, environmental scanning electron microscopy, and various optical techniques have greatly enhanced the study of these stages. Even so, the exact cause (or causes) of particle deformation is still a topic of considerable debate. Several factors are experimentally known to influence latex film formation: the ambient conditions; the presence of surfactants, plasticizers and pigments; and latex particle structure. An important aim in the study of latex film formation is to understand the mechanisms by which these and other factors affect the process. New challenges lie in the study of film formation of core-shell latices, latex blends and new compositions. © 1997 Elsevier Science S.A.

  • Keddie JL, Meredith P, Jones RAL, Donald AM. (1996) 'Film formation of acrylic latices with varying concentrations of non-film-forming latex particles'. Langmuir, 12 (16), pp. 3793-3801.

    Abstract

    We have employed ellipsometry and environmental SEM (ESEM) to determine the kinetics of film formation in mixtures of film-forming (FF) and non-film-forming (NFF) acrylic latices. We find that an increasing concentration of NFF latex leads to progressively larger voids. We have also found that minimizing the number of NFF-NFF particle contacts within the mixture results in a denser material. The rate of void closure during the early stages of film formation is enhanced by the presence of NFF latex particles, because the particles lead to a higher surface area that provides a stronger driving force for void closure. Despite this effect, a latex with a higher concentration of NFF particles takes longer to reach full density. We have applied the Mackenzie-Shuttleworth theory to our densification data and found a value for the viscosity of the FF latex that is consistent with the literature. In some cases, we see evidence for polymer viscosity changing with time, indicative of hydroplasticization. We find that our calculated viscosity of the FF latex decreases with increasing temperature and increases with the addition of 40 wt % NFF particles. We comment on the implications that this work has for the measurement of the critical pigment volume concentration.

  • Keddie JL, Meredith P, Jones RAL, Donald AM. (1996) 'Rate-Limiting Steps in Film Formation of Acrylic Latices as Elucidated with Ellipsometry and Environmental Scanning Electron Microscopy'. ACS Symposium Series, 648, pp. 332-348.

    Abstract

    Our data indicate that evaporation is the rate-limiting step in film formation when the temperature of a latex is about 20 K or more above its glass transition temperature (T). When a latex is nearer to its T, the rate-limiting step in film formation is deformation of the latex particles, possibly by viscous flow of the polymer driven by the reduction in surface energy. In this latter case, there is evidence that a drying front first creates air voids. Subsequently, a coalescence front moves inward from the periphery in the plane of the film. Evaporation rates are retarded in a latex that is well-above its T, probably as a result of the reduced surface area of water, caused by extensive particle deformation. We studied the kinetics of film formation in an acrylic latex using ellipsometry and environmental-SEM, techniques which allow in situ observation of wet and partially-wet latices. We fit our data to a model describing the coalescence of voids by viscous flow.

  • KEDDIE J, MEREDITH P, JONES R, DONALD A. (1995) 'RATE-LIMITING STEPS IN THE FILM FORMATION OF WATER-BORNE ACRYLIC LATTICES AS ELUCIDATED WITH ELLIPSOMETRY AND ENVIRONMENTAL-SEM'. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 210, pp. 76-PSME.
  • KEDDIE J, JONES R. (1995) 'GLASS-TRANSITION BEHAVIOR IN ULTRA-THIN POLYSTYRENE FILMS'. ISRAEL JOURNAL OF CHEMISTRY, 35 (1), pp. 21-26.
  • Keddie JL, Jones RAL. (1995) 'Depression of the glass transition temperature in ultra-thin, grafted polystyrene films'. Materials Research Society Symposium - Proceedings, 366, pp. 183-188.

    Abstract

    We have used ellipsometry to measure the glass transition temperature (T) of ultra-thin films of polystyrene (PS) (less than 10 nm thick) obtained by grafting PS-COOH on the native oxide of Si. We find that T in these ultra-thin films is depressed from the bulk value by as much as 35 K. This is in qualitative accord with our earlier results on thicker non-grafted films of PS.

  • Keddie JL, Meredith P, Jones RAL, Donald AM. (1995) 'Kinetics of film formation in acrylic latices studied with multiple-angle-of-incidence ellipsometry and environmental SEM'. Macromolecules, 28 (8), pp. 2673-2682.

    Abstract

    A combination of multiple-angle-of-incidence ellipsometry (MAIE) and environmental SEM (ESEM) was used to characterize the microstructure of acrylic latices during all four stages of film formation, starting from an aqueous colloidal dispersion (Stage I) and evolving to a continuous coating having no internal solid-solid interfaces (Stage IV). Stage II is usually defined as a close-packed array with water-filled interstices, and Stage III is defined as a densely packed array of deformed particles. This analysis identified an additional stage, II*, intermediate to the conventionally defined Stages II and III. The onset of this new stage, which coincides with the development of optical clarity, occurs at nearly the same time (normalized by the final film thickness), regardless of the glass transition temperature (T) of the latex polymer. The duration of Stage II* and the kinetics of particle coalescence in Stage III, on the other hand, are a function of T. A latex with a T well below the ambient temperature can deform rapidly to fill the space left by the evaporation of water. A latex with a higher T cannot, and so air voids and surface roughness develop and persist over measurable times.

  • KEDDIE J, JONES R, CORY R. (1994) 'SIZE-DEPENDENT DEPRESSION OF THE GLASS-TRANSITION TEMPERATURE IN POLYMER-FILMS'. EUROPHYSICS LETTERS, 27 (1), pp. 59-64.
  • KEDDIE J, BRAUN P, GIANNELIS E. (1994) 'INTERRELATIONSHIP BETWEEN DENSIFICATION, CRYSTALLIZATION, AND CHEMICAL EVOLUTION IN SOL-GEL TITANIA THIN-FILMS'. JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 77 (6), pp. 1592-1596.
  • KEDDIE J, JONES R, CORY R. (1994) 'INTERFACE AND SURFACE EFFECTS ON THE GLASS-TRANSITION TEMPERATURE IN THIN POLYMER-FILMS'. FARADAY DISCUSSIONS, 98, pp. 219-230.
  • KEDDIE J, BRAUN P, GIANNELIS E. (1993) 'RELATIONSHIP BETWEEN WATER DESORPTION AND LOW-TEMPERATURE DENSIFICATION OF COLLOIDAL ANATASE THIN-FILMS'. JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 76 (10), pp. 2529-2533.
  • KEDDIE J, NORTON L, KRAMER E, GIANNELIS E. (1993) 'NEUTRON REFLECTOMETRY CHARACTERIZATION OF INTERFACE WIDTH BETWEEN SOL-GEL TITANIUM-DIOXIDE AND SILICON DIOXIDE THIN-FILMS'. JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 76 (10), pp. 2534-2538.
  • LEVINE T, KEDDIE J, REVESZ P, MAYER J, GIANNELIS E. (1993) 'ION-BEAM-INDUCED DENSIFICATION OF ZIRCONIA SOL-GEL THIN-FILMS'. JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 76 (5), pp. 1369-1379.
  • KEDDIE J, LI J, MAYER J, GIANNELIS E. (1991) 'EFFECT OF NITRIDATION RATE ON THE COMPOSITION AND CONDUCTIVITY OF TITANIUM NITRIDE FILMS PREPARED FROM SOL-GEL TITANIA'. JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 74 (11), pp. 2937-2940.
  • KEDDIE J, GIANNELIS E. (1991) 'EFFECT OF HEATING RATE ON THE SINTERING OF TITANIUM-DIOXIDE THIN-FILMS - COMPETITION BETWEEN DENSIFICATION AND CRYSTALLIZATION'. JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 74 (10), pp. 2669-2671.
  • Mehrotra V, Keddie JL, Miller JM, Giannelis EP. (1991) 'Electrically conducting glasses: incorporation of polypyrrole in a porous SiO matrix'. Journal of Non-Crystalline Solids, 136 (1-2), pp. 97-102.

    Abstract

    Electrically conducting glasses have been synthesized by incorporating polypyrrole in an SiO sol-gel derived glass matrix. Adsorption of pyrrole in the porous network of Cu-containing silica gels, in both bulk and thin film form, results in an oxidative polymerization to polypyrrole as demonstrated by electronic, infrared and Raman spectroscopies. Upon doping with iodine vapors, the polypyrrole-glass hybrids become electrically conducting with an average room temperature dc conductivity of 2 × 10 S/cm in the bulk and 3 × 10 S/cm in thin film form. DC conduction is described by a variable-range hopping model. The dielectric response of the hybrids is characteristics of conductor-insulator composites. © 1991.

  • Keddie JL, Giannelis EP. (1990) 'Ion-beam analysis of silica sol-gel films. Structural and compositional evolution'. Journal of the American Ceramic Society, 73 (10), pp. 3106-3109.

    Abstract

    Rutherford backscattering and forward recoil spectrometry have been used to determine the chemical composition and density of SiO sol-gel films. The as-deposited films are relatively dense, because of considerable interpenetration of weakly branched silicate precursors, while they contain significant amounts of hydroxyl groups in their structure. Annealing in flowing Ar increases the density of the films with values approaching that of amorphous silica at temperatures as low as 450°C but it fails to completely remove all the hydroxyl groups from the structure.

Conference papers

  • Keddie JL, Georgiadis A, Sansom H, Muhamad F. (2013) 'Bespoke patterned coatings via infrared radiation-assisted evaporative lithography: Moving colloids with modulated light'. AMER CHEMICAL SOC ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, New Orleans, LA: 245th National Meeting of the American-Chemical-Society (ACS) 245
  • Keddie JL, Utgenannt A, Kanaras AG, Muskens OL. (2013) 'Directed organization of gold nanoparticles in polymer coatings over large length scales through infrared-assisted evaporative lithography'. AMER CHEMICAL SOC ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, New Orleans, LA: 245th National Meeting of the American-Chemical-Society (ACS) 245
  • Keddie JL, Gurney R, Dupin D, Siband E. (2013) 'Large-area patterning of the tackiness of a colloidal nanocomposite adhesive by sintering of nanoparticles under IR radiation'. AMER CHEMICAL SOC ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, New Orleans, LA: 245th National Meeting of the American-Chemical-Society (ACS) 245
  • Daar E, Woods E, Keddie JL, Nisbet A, Bradley DA. (2010) 'Effect of penetrating ionising radiation on the mechanical properties of pericardium'. ELSEVIER SCIENCE BV NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, Melbourne, AUSTRALIA: 11th International Symposium on Radiation Physics 619 (1-3), pp. 356-360.
  • Mills CA, Intaniwet A, Shkunov M, Keddie JL, Sellin PJ. (2009) 'Flexible radiation dosimeters incorporating semiconducting polymer thick films'. SPIE Proceedings of SPIE - The International Society for Optical Engineering, San Diego, USA: Hard X-ray, gamma-ray, and neutron detector physics XI 7449

    Abstract

    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 (<0.2 nA).

  • Deplace F, Marchal J, Carelli C, Chateauminois A, Creton C, Rabjohns M, Foster A, Lovell PA, Lei C, Keddie J. (2009) 'Soft-soft nanocomposites for adhesive applications'. 12th International Conference on Fracture 2009, ICF-12, Ottawa, Canada: 2, pp. 1205-1211.
  • Ekanayake P, McDonald PJ, Keddie JL. (2009) 'An experimental test of the scaling prediction for the spatial distribution of water during the drying of colloidal films'. EDP SCIENCES S A/SPRINGER EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS, Paris, FRANCE: 7th Biannual European Coating Symposium 166 (1), pp. 21-27.
  • Simpson TRE, Keddie JL, Parbhoo B. (2003) 'Influence of interfaces on the rate of crosslinking in silicone coatings.'. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 225, pp. U710-U710.
  • Simpson TRE, Keddie JL, Parbhoo B. (2003) 'IR ellipsometry of crosslinking in silicone coatings: Effect of thickness'. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 225, pp. U702-U702.
  • Selvakumaran J, Hughes MP, Keddie JL, Ewins DJ. (2002) 'Assessing biocompatibility of materials for implantable microelectrodes using cytotoxicity and protein adsorption studies'. 2ND ANNUAL INTERNATIONAL IEEE-EMBS SPECIAL TOPIC CONFERENCE ON MICROTECHNOLOGIES IN MEDICINE & BIOLOGY, PROCEEDINGS, , pp. 261-264.
  • Hellgren AC, Wallin M, Weissenborn PK, McDonald PJ, Glover PM, Keddie JL. (2001) 'New techniques for determining the extent of crosslinking in coatings'. ELSEVIER SCIENCE SA PROGRESS IN ORGANIC COATINGS, ATHENS, GREECE: Conference on Organic Coatings and Technology 43 (1-3), pp. 85-98.
  • Styrkas D, Doran SJ, Gilchrist T, Keddie JL, Lu JR, Murphy E, Sackin R, Su TJ, Tzitzinou A. (1999) 'Application of ellipsometry to polymers at interfaces and in thin films'. POLYMER SURFACES AND INTERFACES III, , pp. 1-42.
  • Keddie JL, Cory RA, Jones RAL. (1998) 'Polymer dynamics in thin films'. MODERN ASPECTS OF COLLOIDAL DISPERSIONS, , pp. 149-157.
  • Keddie JL, Meredith P, Jones RAL, Donald AM. (1998) 'Film formation of latices'. MODERN ASPECTS OF COLLOIDAL DISPERSIONS, , pp. 51-59.

Books

  • Routh AF, Keddie J. (2010) Fundamentals of Latex Film Formation: Processes and Properties. Springer Verlag

    Abstract

    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.

Teaching

Year 1: Properties of Matter (PHY1039) - lectures and laboratory

Year 3: Soft Matter and Biological Physics (PHY3040)

MSc in Advanced Materials:  Lectures on Polymers and Nanomaterials

Departmental Duties

Senior Tutor for Professional Training: responsible for the one-year placement programme for BSc students

Formerly Leader of the Soft Matter Group

Research News

We have funding for a PhD student (tuition fees plus £14,000/year for living expenses) to develop polymer colloid coatings for seeds.  The project is sponsored by Syngenta.  To apply send your CV and covering letter to Professor Keddie.

We have recently joined the BARRIER-PLUS project (FP7), and we are now recruiting two post-doctoral researchers: an experimentalist to study film formation and a theorist to model the process.

We have recently moved into refurbished laboratory space.  Have a look on a virtual tour here.  We also have access to a new thermal analysis laboratory shown here.

Our report of a new method to make patterned polymer coatings using IR-assisted evaporative lithography has been highlighted on the inside front cover of Soft Matter. The research was also reported in Eureka magazine and The Engineer. We have also applied for an international patent on the technology.

Professor Keddie's lecture at the Coatings Science International (CoSI) meeting in 2012 won the Innovation Prize.

My PhD student, Robert Gurney, has won a prize for his poster on switchable adhesives, which was presented at the Adhesion '11 meeting, organised by the IOM3.

Research by my former PhD student, Tao Wang, which was carried out in collaboration with the research team of Stefan Bon at the University of Warwick, has recently appeared as the cover article in Soft Matter. The paper shows how nanocomposite particles of clay and polymers can be used to increase the adhesion energy of polymer films.

My 1994 paper on the reduced glass transition temperature in polymer thin films, which was co-authored with Professor Richard Jones (now at the University of Sheffield), has been named as one of the 25 most-cited articles in the Europhysics Letters archive.

Posters by Tecla Weerakkody (Soft Matter PhD student) and Dr. Carolina de las Heras (post-doctoral fellow) won prizes at the UK Polymer Colloids Forum meeting at the University of Greenwich in August 2008.

A paper written by part-time PhD student, Nicki Kessel, and me has won the 2007 Roon Award (Second Place) from the Federation of Societies for Coatings Technology.  Nicki collected the prize (a plaque and a cheque) in Toronto in October.

Our research with Dr. Paul Sellin, which showed that conjugated polymers can be used for the direct detection of X-radiation, has been highlighted in Laser Focus World.

Tecla Weerakkody, a Soft Matter PhD student,  won the BASF Poster Prize at the International Conference on Polymer Colloids, held at the University of Warwick in September 2007.

Mr. Tao Wang, who is a PhD student working with Joe Keddie and Alan Dalton, has won the "Best Student Paper Prize" from the Polymer Physics Group of the Institute of Physics.  Wang presented his prize-winning paper at the Biennial Meeting in Durham in September 2007.

Our recent work on waterborne, nanocomposite adhesives having electrical conductivity and optical clarity has been featured in the  "Spotlight" on the Nanowerk website on nanotechnology news.  This work was also selected by the editors of Science magazine for their "Editor's Choice" column on November 17th 2006.  (The link requires a subscription to Science.) Mark Levine wrote that the properties of our adhesives "bode well for eventual applications of this relatively environmentally benign material in electronics and displays."  Below is a photograph of the de-bonded surface of an adhesive that is a nanocomposite of carbon nanotubes and poly(butyl acrylate). 

Joe Keddie gave an invited lecture at the Tess Award Symposium in honour of Prof. "Skip" Scriven at the 234th ACS Meeting in Boston in August 2007.  He also gave an invited lecture at the European Coatings Symposium in Paris.

Professional Activities

Page Owner: phs1jk
Page Created: Monday 10 August 2009 12:57:16 by lb0014
Last Modified: Thursday 9 January 2014 16:45:26 by phs1jk
Expiry Date: Wednesday 10 November 2010 12:56:21
Assembly date: Fri Oct 31 17:15:21 GMT 2014
Content ID: 11683
Revision: 15
Community: 1256