Dr Peter J. Roth

Lecturer in Applied Organic Chemistry
Dipl.-Chem. Dr. rer. nat., MRSC



Research interests

Research projects

My teaching


Postgraduate research supervision

My publications


Roth PJ, Theato P (2012) Covalent Attachment of Gold Nanoparticles to Surfaces and Polymeric Substrates Using UV Light, MACROMOLECULAR CHEMISTRY AND PHYSICS 213 (23) pp. 2550-2556 WILEY-V C H VERLAG GMBH
Uniform benzophenone-covered AuNP (Bph-AuNP) were prepared in a two-phase ethyl acetate/water
reduction of auric acid employing a benzophenone-functionalized disulfi de. Upon
UV irradiation, the benzophenone carbonyl bond was excited allowing for insertion into a
nearby C?H bond and thus a covalent attachment of the AuNP
onto a substrate exhibiting C?H bonds. Using this technique,
polycarbonate?gold core?shell particles were easily obtained,
providing a simple synthetic pathway toward AuNP hybrids
with polycondensation polymers. Bph-AuNP were also covalently
attached to alkylated silica microspheres or cellulose
paper. UV irradiation through a photo mask enabled a photolithographic
surface patterning.
Albuszis M, Roth PJ, Exnowitz F, Wong DL, Pauer W, Moritz H-U (2016) Synthesis and in-depth characterization of reactive, uniform, crosslinked microparticles based on free radical copolymerization of 4-vinylbenzyl azide, Polymer Chemistry 7 (5) pp. 1168-1180 Royal Society of Chemistry
The introduction of functional groups into microparticles is commonly accomplished through, at times, low-yielding post-synthesis modification. In this detailed study, the introduction of azide functionality into uniform, crosslinked, macroporous microparticles through direct copolymerization of styrene, divinylbenzene (DVB), and 4-vinylbenzyl azide (VBA) in varying ratios inside swollen polystyrene seed (template) particles is investigated. Formulations contained up to 40 wt% of VBA in the monomer mixture. Resulting microspheres were characterised by SEM, porosimetry, FT-IR spectroscopy, and CHN elemental analysis. Uniform spherical particles with diameters ranging from 7.3 to 10.8 ¼m with diameter dispersities typically below 1.01 and with tuneable azide loadings from 0.11 to 1.17 mmol g?1 were obtained. Interestingly, severe effects of VBA addition on porosity, surface smoothness, and particle shape were observed. Specific surface areas and cumulative pore volumes increased with the amount of DVB in feed, decreased with increasing VBA feed ratio, and increased drastically for the use of azide-functional template particles with measured cumulative pore volumes reaching up to 0.60 cm3 g?1. With increasing VBA feed, formation of smaller, secondary particles was observed and attributed to an incomplete swelling of VBA into seed particles, which is discussed as a main reason for lower-than-expected azide contents in product particles. For high VBA feed ratios (>25 wt%), dented, hollow, or hollow collapsed azide-functional particles were found, presumably due to immiscibility of the growing azide-functional copolymer with the polystyrene seeds. Finally, successful click-modification is demonstrated with phenylacetylene and an alkyne-functional Rhodamine B dye allowing for mapping of functionalization density through confocal fluorescence microscopy.
van Hensbergen JA, Ganda S, Roth PJ, Burford RP, Lowe AB (2015) ROMP Synthesis of Novel Thermo-, pH-, and Salt-Responsive (Co)Polymers Containing the Morpholino Functional Group, JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY 53 (1) pp. 50-58 WILEY-BLACKWELL
We report the ring-opening metathesis polymerization (ROMP) synthesis of novel (co)polymers containing the multiresponsive morpholino functional group [(3aR,7aS)?2-(2-morpholinoethyl)?3a,4,7,7a-tetrahydro-1H?4,7-epoxyisoindole-1,3(2H)-dione (M1)]. All (co)polymers were prepared with the Grubbs' first generation initiator, RuCl2(PCy3)2CHPh, in CH2Cl2 or CH2Cl2/2,2,2-trifluoroethanol solvent mixtures. M1 homopolymers exhibit a pH dependent aqueous solubility being fully soluble below pH 5.0 and above pH 6.0. At these intermediate values, the polymers exhibit molecular weight (MW) independent inverse temperature dependent solubility with measured cloud points (TCP) of 86 °C at pH 5.0 and 79 °C at pH 6.0. In the case of the lowest MW homopolymer (absolute MW of 9950 g/mol), there was a clear dependence of the TCP on the homopolymer solution concentration and varied over the range 78?88 °C. The TCP could be further tuned via the preparation of novel AB statistical copolymers. Incorporation of a permanently cationic comonomer as a more hydrophilic species resulted in an increase of the TCP at low incorporations (up to 10 mol %) and the complete disappearance of any temperature dependent solubility at 20 mol %. In a complementary approach, the TCP could also be lowered by the preparation of statistical copolymers of M1 with a more hydrophobic comonomer. Finally, we note that M1 homopolymers are also responsive to Na2SO4 and could be readily salted-out of an aqueous solution salt at a [Na2SO4] of 2.0 M giving a third trigger for controlling aqueous solubility. These copolymers represent examples of new multiresponsive materials and demonstrate the effectiveness of ROMP as a synthetic tool for the preparation of new and interesting materials.
Albuszis M, Roth PJ, Pauer W, Moritz H-U (2014) Macroporous uniform azide- and alkyne-functional polymer microspheres with tuneable surface area: synthesis, in-depth characterization and click-modification, POLYMER CHEMISTRY 5 (19) pp. 5689-5699 ROYAL SOC CHEMISTRY
A series of uniform, macroporous poly(styrene-co-divinylbenzene) microspheres with diameters ranging from 6.6 0.6 to 8.6 0.2 mm was prepared in a multistep procedure involving precipitation

polymerization synthesis of polystyrene seed particles, swelling of seed particles with plasticiser and porogen, and polymerization of styrene?divinylbenzene (S?DVB) inside the seed particles. Particles prepared with varying DVB feed ratios had comparable diameters (as evidenced by scanning electron microscopy) with speci?c surface areas increasing with DVB content from 11 to 467 m2 g1 (measured by nitrogen adsorption). Residual double bonds were converted into azide functionality (through HBr addition and bromo-azide substitution) or alkyne functionality (Br2 addition followed by double elimination) which allowed for CuAAC-click chemistry conjugation with reagents carrying the respective complimentary alkyne or azide functional groups including the ?uorescent dye derivatives 7-nitro-4-(prop-2-ynylamino)benzofuran (NBD-alkyne) and Rhodamine B hexylazide synthesised for this purpose. E?ciency of chemical transformations was determined using a combination of CHN and IC elemental analyses, solid state NMR spectroscopy, FT-IR spectroscopy, Raman spectroscopy, and confocal scanning ?uorescence microscopy. Although the respective second steps in each modi?cation route (substitution and elimination) su?ered from lower yields (35%), porous particles with azide loadings of

up to 0.71 mmol g1 and alkyne loadings of up to 0.78 mmol g1 were prepared. Confocal laser scanning microscopy on Rhodamine B-labelled microspheres indicated functionalization throughout the particles featuring a core?shell structure with higher functionalization in the outer layer of particles.

Results are expected to contribute to the development of advanced, well-de?ned, macroporous particles with high, chemically accessible surface areas.

Roth P, Theato P (2010) End group functionalization of RAFT polymers using thiol alkyl methanethiosulfonate click-like chemistry, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 240 AMER CHEMICAL SOC
Bhebhe Mathamsanqa N., Alvarez De Eulate Eva, Pei Yiwen, Arrigan Damien W. M, Roth Peter J., Lowe Andrew B. (2016) Reactive Conjugated Polymers: Synthesis, Modification and Electrochemical Properties of Polypentafluorophenylacetylene (Co) Polymers, MACROMOLECULAR RAPID COMMUNICATIONS 38 1600450 WILEY-V C H VERLAG GMBH
(Co)Polymers containing pentafluorophenylacetylene (F5PA) have been prepared for the first time mediated by [Rh(nbd)Cl]2/NEt3 to give materials with properties typical of poly(phenylacetylene)s prepared with this catalyst/co-catalyst combination. We demonstrate that the F5PA repeat units in these new (co)polymers serve as convenient reactive species for postpolymerization modification with thiols via para-fluoro aromatic nucleophilic substitution reactions to give an entirely new family of novel thioether-functional polyene materials accompanied by absorption maxima shifts of up to 130 nm. Finally, we briefly examine the electrochemical properties of these new fluorinated polyene materials and highlight the distinct difference in behaviour of the F5PA homopolymer versus polyphenylacetylene, copolymers and functional derivatives.
Roth PJ, Theato P (2015) Polymer Analogous Reactions, In: Hashmi MSJ (eds.), Reference Module in Materials Science and Materials Engineering pp. 1-27 Elsevier
Polymer analogous reactions represent a synthetically very appealing approach for the synthesis of functional polymers. Different synthetic concepts of organic reactions are merging in polymer science leading toward the synthesis of architecturally well-defined multifunctional polymers. The different classes of reactions provide the synthetic polymer chemist with tools of unprecedented precision, thereby opening the doors for materials synthesis in an interdisciplinary world.
Roth PJ, Boyer C, Lowe AB, Davis TP (2011) RAFT Polymerization and Thiol Chemistry: A Complementary Pairing for Implementing Modern Macromolecular Design, MACROMOLECULAR RAPID COMMUNICATIONS 32 (15) pp. 1123-1143 WILEY-V C H VERLAG GMBH
Reversible addition fragmentation chain transfer (RAFT) polymerization is one of the most
extensively studied reversible deactivation radical polymerization methods for the production
of well-defined polymers. After polymerization, the RAFT agent end-group can easily be
converted into a thiol, opening manifold opportunities
for thiol modification reactions. This review is focused
both on the introduction of functional end-groups using
well-established methods, such as thiol-ene chemistry, as
well as on creating bio-cleavable disulfide linkages via
disulfide exchange reactions. We demonstrate that thiol
modification is a highly attractive and efficient chemistry
for modifying RAFT polymers.
Krishna O, Wiss K, Roth P, Theato P, Kiick K (2009) Assembly of thermally responsive, collagen peptide-containing block copolymers, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 238 AMER CHEMICAL SOC
Roth PJ, Theato P (2016) Polymer Analogous Reactions, Reference Module in Materials Science and Materials Engineering pp. 1-27 Elsevier
Roth PJ, Davis TP, Lowe AB (2014) Novel ±,±-bischolesteryl functional (co)polymers: RAFT radical polymerization synthesis and preliminary solution characterization., Macromol Rapid Commun 35 (8) pp. 813-820
Well-defined poly[pentafluorophenyl (meth)acrylate] (PPFP(M)A) homopolymers are prepared by RAFT radical polymerization mediated by a novel chain transfer agent containing two cholesteryl groups in the R-group fragment. Subsequent reaction with a series of small-molecule amines in the presence of an appropriate Michael acceptor for É-group end-capping yields a library of novel bischolesteryl functional hydrophilic homopolymers. Two examples of statistical copolymers are also prepared including a biologically relevant sugar derivative. Specific examples of these homopolymers are examined with respect to their ability to self assemble in aqueous media-a process driven entirely by the cholesteryl end groups. In all instances evaluated, and under the preparation conditions examined, the homopolymers aggregate clearly forming polymersomes spanning an impressive size range.
Pei Y, Sugita OR, Quek JY, Roth PJ, Lowe AB (2015) pH-, thermo- and electrolyte-responsive polymer gels derived from a well-defined, RAFT-synthesized, poly(2-vinyl-4,4-dimethylazlactone) homopolymer via one-pot post-polymerization modification, EUROPEAN POLYMER JOURNAL 62 pp. 204-213 PERGAMON-ELSEVIER SCIENCE LTD
Well-de?ned stimulus-responsive polymer gels were prepared from poly(2-vinyl-4,4-dimethylazlatone) (PVDMA) via one-pot post-polymerization modi?cation. VDMA homo-polymers were reacted with diamine crosslinking agents and functional 1 or 2 amines to form polymer gels that swelled in organic solvents and, in many cases, aqueous solu-tions. A series of functional amine reagents, including N,N-dimethylethylenediamine (DMEDA), N,N-diethylethylenediamine (DEEDA), morpholine, 3-morpholinopropylamine

(MPPA) and tetrahydrofurfurylamine (THFA), were chosen as functional amines to produce polymer gels containing environmentally sensitive species. 13C solid-state NMR and FTIR spectroscopic measurements con?rmed complete conversion of the reactive scaffolds. pH-dependent swelling behavior at ambient temperature was observed in DMEDA-, DEE-DA- and MPPA-modi?ed hydrogels. Kinetic studies showed the swelling behaviors of DME-DA-modi?ed hydrogels were regulated by cross-linker type and concentration in acidic water (pH = 4) at ambient temperature. The swelling ratio of hydrogels modi?ed by DEE-DA, MPPA and THFA also depended strongly on temperature, indicating successful synthe-sis of thermoresponsive gels. Furthermore, the concentration of added sodium sulfate played a signi?cant role with respect to the swelling properties of MPPA-modi?ed hydro-gels. These smart materials may be of interest in the biomedical ?eld as well as in other applications.

Schmidt S, Koldevitz M, Noy J-M, Roth PJ (2015) Multicomponent isocyanide-based synthesis of reactive styrenic and (meth)acrylic monomers and their RAFT (co) polymerization, POLYMER CHEMISTRY 6 (1) pp. 44-54 ROYAL SOC CHEMISTRY
The multicomponent Passerini reaction of aldehydes, carboxylic acids, and isocyanides is used to produce a series of novel reactive (meth)acrylic and styrenic monomers carrying pendant double bond, (trimethylsilyl protected) triple bond, diene, acetate, or pentafluorophenyl functionality. Dichloromethane and water were compared as solvents in the synthesis of 15 different monomers, with water resulting in significantly higher, up to quantitative, isolated yields with minimal purification. Characterization by 1H, 13C, and 19F NMR spectroscopy, FT-IR spectroscopy and mass spectrometry confirmed the synthesis and high purity of the functional ±-acyloxycarboxamide products. The monomers are shown to be well suited for the RAFT-synthesis of well-defined homopolymers, statistical copolymers with methyl methacrylate, poly(ethylene glycol) methyl ether methacrylate, and styrene, statistical copolymers produced from two different Passerini-derived monomers, and AB diblock copolymers. SEC-measured polydispersities were generally low, ?M d 1.29, and 1H NMR spectroscopy confirmed copolymer molar compositions in good agreement with comonomer feed ratios. We expect this synthetic strategy to provide access to a wide range of novel multifunctional materials and demonstrate preliminary postpolymerization modification of a polystyrene derivative by cleavage of its pendent acetate groups and coupling of the dye Methyl Red to the resulting alcohol groups.
Jochum FD, zur Borg L, Roth PJ, Theato P (2009) Thermo- and Light-Responsive Polymers Containing Photoswitchable Azobenzene End Groups, MACROMOLECULES 42 (20) pp. 7854-7862 AMER CHEMICAL SOC
Telechelic thermo- and light-responsive polymers based on poly(oligo(ethylene glycol)
methyl ether methacrylate) P(OEGMA) with azobenzene functionalities at the end groups were synthesized.
In a reversible addition-fragmentation chain transfer (RAFT) polymerization using a functionalized chain
transfer agent (CTA) containing a pentafluorophenyl (PFP) activated ester, oligo(ethylene glycol) methyl
ether methacrylate (OEGMA, Mn ) could successfully be polymerized with good control over
molecular weight, very high conversions, and narrow molecular weight distributions. Polymers derived from
this CTA possessed an activated ester at the R-end of the polymer chain as well as a dithioester É-terminus.
The É-dithioester group of each polymer chain could quantitatively be either removed with AIBN treatment
or substituted with a PFP ester by using a modified diazo compound. As a consequence, a postmodifiaction of
the telechelic reactive end groups was possible through a polymer analogous reaction with aminofunctionalized
azobenzene. P(OEGMA) polymers containing azobenzene end groups showed a reversible
light- and temperature-controlled phase transition in water. Higher values for the lower critical solution
temperature (LCST) were measured after irradiation of the aqueous polymer solutions due to the higher
polarity of cis-azobenzene. The LCST differences between irradiated and nonirradiated solutions increased
linearly upon the ratio of azobenzene units up to 4.3 C
Quek JY, Roth PJ, Evans RA, Davis TP, Lowe AB (2013) Reversible addition-fragmentation chain transfer synthesis of amidine-based, CO2-responsive homo and AB diblock (Co)polymers comprised of histamine and their gas-triggered self-assembly in water, JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY 51 (2) pp. 394-404 WILEY-BLACKWELL
Well-defined homopolymers of pentafluorophenyl acrylate
(PFPA) and AB diblock copolymers of N,N-dimethylacrylamide
(DMA) and poly(ethylene glycol) methyl ether acrylate
(PEGA) with PFPA were prepared by reversible addition?fragmentation
chain transfer (RAFT) radical polymerization. Three PFPA
homopolymers of different molecular weights were reacted with
the commercially available amidine and guanidine species histamine
(HIS) dihydrochloride and L-arginine methyl ester (ARG)
dihydrochloride in the presence of S-methyl methanethiosulfonate
to yield, quantitatively, the corresponding amidine and guanidinebased
acrylamido homopolymers. Both the HIS and ARG homopolymers
are known to reversibly bind CO2 with, in the case of
the former, CO2 fixation being accompanied with a switch from a
hydrophobic to hydrophilic state. The RAFT synthesis of PFPADMA
and PEGA-PFPA diblock copolymers yielded well-defined
materials with a range of molar compositions. These precursor
materials were converted to the corresponding HIS and ARG
block copolymers whose structure was confirmed using 1
spectroscopy. Employing a combination of dynamic light scattering
and transmission electron microscopy, we demonstrate that
the DMA-HIS and PEGA-HIS diblock copolymers are able to
undergo reversible and cyclable self-directed assembly in aqueous
media using CO2 and N2 as the triggers between fully hydrophilic
and amphiphilic (assembled) states. For example, in the
case of the 54:46 DMA-HIS diblock, aggregates with hydrodynamic
diameters of about 40.0 nm are readily formed from the
molecularly dissolved state.
Krishna OD, Wiss KT, Roth PJ, Theato P, Kiick KL (2010) Conformational and assembly behavior of collagen-mimetic peptides and their thermally responsive polymer conjugates, Polymer Preprints 51 pp. 49-50 American Chemical Society
A novel class of thiol-reactive (meth)acrylate monomers and the quantitative postpolymerization modifi-
cation of their RAFT-made (co)polymers with aromatic, glycosidic, and aliphatic thiols are presented. A set
of 6 different N-functional 2-(meth)acryloyloxy-2-(pentafluorophenyl)acetamide monomers bearing
pentafluorophenyl groups was prepared by a Passerini three-component reaction of (meth)acrylic acid,
2,3,4,5,6-pentafluorobenzaldehyde, and various isocyanides in water in up to near-quantitative isolated
yields. RAFT polymerization was used to produce well-defined homopolymers and copolymers with
methyl methacrylate, tert-butyl methacrylate, poly(ethylene glycol) methyl ether (meth)acrylate, and
pentafluorophenyl acrylate, with low polydispersity indices of generally ?M d 1.23. In the presence of
base, (co)polymers underwent selective para-fluoro substitution reactions with thiols in the absence of any
side reactions observable by 1
H and 19F NMR spectroscopy and size exclusion chromatography. The selection
of employed thiols included various alkanethiols, a thiolated glucose derivative, mercaptopropionic
acid, L-cysteine and the drug captopril. 19F NMR kinetic measurements indicated quantitative thiol?para-
fluoro substitutions after the employed thiol (aromatic, glycosidic > primary aliphatic > secondary aliphatic > tertiary aliphatic) and the
choice of a suitable base (triethylamine or 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)). The versatility of
thiol-reactive (meth)acrylate species is demonstrated by the examples of a thermoresponsive copolymer
showing a thiol-sensitive lower critical solution temperature (LCST) and the selective sequential modification
with thiols and amines of a doubly reactive copolymer containing activated pentafluorophenyl esters
Krishna OD, Wiss KT, Roth PJ, Theato P, Kiick KL (2009) Assembly of thermally responsive, collagen peptide-containing block copolymers, PMSE Prepr. 101 pp. 1477-1478 American Chemical Society
Roth PJ, Quek JY, Zhu Y, Blunden BM, Lowe AB (2014) Mechano-responsive polymer solutions based on CO2 supersaturation: shaking-induced phase transitions and self-assembly or dissociation of polymeric nanoparticles, CHEMICAL COMMUNICATIONS 50 (67) pp. 9561-9564 ROYAL SOC CHEMISTRY
Mechanical stimulation of supersaturated aqueous CO2 solutions is accompanied by a pH increase within seconds. In solutions of tailored homo- and AB diblock copolymers this is exploited to induce micelle formation, or, taking advantage of an aqueous upper critical solution temperature transition, nanoparticle disassembly.
Jochum FD, Roth PJ, Theato P (2010) Thermoresponsive polymers: From different functional end groups to block copolymers, Polymer Preprints 51 pp. 363-364 American Chemical Society
Roth PJ, Kessler D, Zentel R, Theato P (2008) A Method for Obtaining Defined End Groups of Polymethacrylates Prepared by the RAFT Process during Aminolysis, MACROMOLECULES 41 (22) pp. 8316-8319 AMER CHEMICAL SOC
Theato P, Roth PJ (2011) Hetero-telechelic alpha,omega functionalized polymers for heterodimeric protein conjugation, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 241 AMER CHEMICAL SOC
Roth PJ, Theato P (2011) Orthogonally Reactive Diblock Copolymers Utilizing Alkyne and Isothiocyanate Groups, NON-CONVENTIONAL FUNCTIONAL BLOCK COPOLYMERS 1066 pp. 23-37 AMER CHEMICAL SOC
Pei Y, Dharsana NC, Van Hensbergen JA, Burford RP, Roth PJ, Lowe AB (2014) RAFT dispersion polymerization of 3-phenylpropyl methacrylate with poly[2-(dimethylamino)ethyl methacrylate] macro-CTAs in ethanol and associated thermoreversible polymorphism, SOFT MATTER 10 (31) pp. 5787-5796 ROYAL SOC CHEMISTRY
Harvison MA, Roth PJ, Davis TP, Lowe AB (2011) End Group Reactions of RAFT-Prepared (Co)Polymers, AUSTRALIAN JOURNAL OF CHEMISTRY 64 (8) pp. 992-1006 CSIRO PUBLISHING
This review highlights the chemistry of thiocarbonylthio groups with an emphasis on chemistry conducted at v or a and v
chain-ends in copolymers prepared by reversible addition?fragmentation chain-transfer (RAFT) radical polymerization.
We begin by giving a general overview of reactions associated with the thiocarbonylthio groups, followed by examples
associated with macromolecular thiols.
Quek JY, Liu X, Davis TP, Roth PJ, Lowe AB (2015) RAFT-prepared alpha-difunctional poly(2-vinyl-4,4-dimethylazlactone)s and their derivatives: synthesis and effect of end-groups on aqueous inverse temperature solubility, POLYMER CHEMISTRY 6 (1) pp. 118-127 ROYAL SOC CHEMISTRY
A series of ?ve novel R-group di-functional phenyl dithiobenzoates have been prepared and utilized in the controlled reversible addition?fragmentation chain transfer (RAFT) radical polymerization of 2-vinyl-4,4-dimethylazlactone (VDMA), yielding a series of homopolymers of similar average degrees of polymeriz-ation but variable ±-end group functionality. Each of the reactive polyVDMA homopolymers was reacted with four di?erent small molecule amines: dimethylamine, diethylamine, N,N-diethylethylenediamine and tetrahydrofurfurylamine yielding a series of novel end-functional materials. The e?ect of the end-groups on the inverse temperature dependent aqueous solubility of the formally hydrophilic homopolymers was then measured and compared to similar materials prepared with benzylpropyltrithiocarbonate as the RAFT agent. In virtually all instances, the introduction of the twin ±-end-groups resulted in overall more hydrophobic species that exhibited cloud points spanning the range 25.1?42.7 °C. Importantly, there was a strong in?uence on the nature of the end groups and the associated solubility characteristics with, in some cases, cloud point behaviour only being observed in polymers with twin end groups while those derived from benzylpropyltrithiocarbonate were fully soluble.
Kessler D, Roth PJ, Theato P (2009) Reactive Surface Coatings Based on Polysilsesquioxanes: Controlled Functionalization for Specific Protein Immobilization, LANGMUIR 25 (17) pp. 10068-10076 AMER CHEMICAL SOC
Polymerization-induced self-assembly (PISA) is an extremely versatile method for the in situ preparation of soft-matter nanoparticles of defined size and morphologies at high concentrations suitable for large-scale production. Recently, certain PISA-prepared nanoparticles have been shown to exhibit reversible polymorphism (?shape-shifting?), typically between micellar, worm-like, and vesicular phases (order?order transitions), in response to external stimuli including temperature, pH, electrolytes, and chemical modification. This review summarises the literature to date and describes molecular requirements for the design of stimulus-responsive nano-objects. Reversible pH-responsive behaviour is rationalised in terms of increased solvation of reversibly ionised groups. Temperature-triggered order?order transitions, conversely, do not rely on inherently thermo-responsive polymers, but are explained based on interfacial LCST or UCST behaviour that affects the volume fractions of the core and stabilizer blocks. Irreversible morphology transitions, on the other hand, can result from chemical post-modification of reactive PISA-made particles. Emerging applications and future research directions of this ?smart? nanoparticle behaviour are reviewed.
Roth PJ, Collin M, Boyer C (2013) Advancing the boundary of insolubility of non-linear PEG-analogues in alcohols: UCST transitions in ethanol-water mixtures, SOFT MATTER 9 (6) pp. 1825-1834 ROYAL SOC CHEMISTRY
Kim J-U, Kim K-H, Haberkorn N, Roth PJ, Lee J-C, Theato P, Zentel R (2010) Two-dimensional self-assembly of disulfide functionalized bis-acylurea: a nanosheet template for gold nanoparticle arrays, CHEMICAL COMMUNICATIONS 46 (29) pp. 5343-5345 ROYAL SOC CHEMISTRY
A new functional bis-acylurea molecule allows a two-stage
self-organization process. It self-organizes?at first?into 2D
nanosheets with disulfide groups at the surface, which act?in
the second stage?as a template for gold nanoparticle arrays.
Boyer C, Soeriyadi AH, Roth PJ, Whittaker MR, Davis TP (2011) Post-functionalization of ATRP polymers using both thiol/ene and thiol/disulfide exchange chemistry, CHEMICAL COMMUNICATIONS 47 (4) pp. 1318-1320 ROYAL SOC CHEMISTRY
In this communication, we report on a new route to the
functionalization of ATRP polymers exploiting their halide
end-groups, which were converted successfully into reactive
disulfide end-groups, using sodium methanethiosulfonate. The
resultant disulfide-terminated polymers could then be reacted
with different functional thiols to yield functional polymers
exploiting either thiol/disulfide exchange chemistry or thiol/ene
??click?? reactions.
Zhu Y, Batchelor R, Lowe AB, Roth PJ (2016) Design of Thermoresponsive Polymers with Aqueous LCST, UCST, or Both: Modification of a Reactive Poly(2-vinyl-4,4-dimethylazIactone) Scaffold, Macromolecules 49 (2) pp. 672-680 American Chemical Society
The synthesis and aqueous solution properties of a family of zwitterionic homo-, co-, and terpolymers derived from poly(2-vinyl-4,4-dimethylazlactone) (pVDMA) with tunable lower and upper critical solution temperatures (LCST and UCST) are presented. A RAFT-made pVDMA precursor was reacted with mixtures of zwitterionic sulfopro-pylbetaine (SPB) amine or sulfobutylbetaine (SBB) amine, tetrahydrofurfurylamine (THF amine), and benzylamine (Bz amine) in varying molar ratios. Products were characterized by variable temperature (VT) NMR spectroscopy, FT-IR spec-troscopy, size exclusion chromatography, turbidity, and VT dynamic light scattering in order to con?rm quantitative postpolymerization modi?cation, determine molar compositions, and elucidate structure?property relationships. Polymers comprising large molar fractions of THF groups showed LCST behavior due to a polarity change of the THF-functional segments, while SPB/SBB-rich samples, including the zwitterionic homopolymers, showed UCST behavior in ultrapure water based on electrostatic polymer?polymer attractions. Binary SPB?THF copolymers were water-soluble between 0 and 90 °C for a large compositional range. Terpolymers comprising molar SPB:THF:Bz ratios of approximately 50:25:25 showed a low LCST and a high UCST (LCST
Roth PJ, Jochum FD, Forst FR, Zentel R, Theato P (2010) Influence of End Groups on the Stimulus-Responsive Behavior of Poly[oligo(ethylene glycol) methacrylate] in Water, MACROMOLECULES 43 (10) pp. 4638-4645 AMER CHEMICAL SOC
The influence of the chemical structure of both end groups onto the lower critical solution
temperature (LCST) of poly[oligo(ethylene glycol) monomethyl ether methacrylate] (POEGMA) in water
was systematically investigated. POEGMA of Mn = 3550 g/mol and Mw/Mn = 1.14 prepared by reversible
addition-fragmentation chain transfer (RAFT) polymerization was equipped with two different functional
end groups in a one-step postpolymerization reaction combining activated esters, functional amines, and
functional methane thiosulfonates. As end groups, n-propyl, n-hexadecyl, di(n-octadecyl), poly(ethylene
glycol)-550 (PEG), 1H,1H-perfluorononyl, azobenzene, and trimethylethylammonium groups were systematically
combined with methyl, n-hexadecyl, and 1H,1H,2H,2H-perfluorooctyl groups. Polymers were
characterized by gel permeation chromatography, dynamic light scattering, and turbidimetry. Hydrophobic
end groups at either end of the polymer chain decreased the LCST. For hydrophobic groups at both ends
of the chain their influence was additive. Two large hydrophobic end groups allowed micelle formation
below the LCST and an LCST higher than to be expected from nonaggregated polymers. The strongest
hydrophobic effect was found for rigid aromatic end groups, which was attributed to their incompatibility
with the flexible polymer chain. Charged end groups increased the LCST and could compensate for the effect
of hydrophobic end groups at the opposite end group. PEG end groups could mask a hydrophobic influence
of the opposite end group and stabilized the LCST.
Roth PJ, Wiss KT, Zentel R, Theato P (2008) Synthesis of Reactive Telechelic Polymers Based on Pentafluorophenyl Esters, MACROMOLECULES 41 (22) pp. 8513-8519 AMER CHEMICAL SOC
A diazo initiator and a chain transfer agent (CTA), both containing a pentafluorophenyl (PFP)
activated ester, were synthesized. In a RAFT polymerization using the functionalized chain transfer agent (PFPCTA),
methyl methacrylate (MMA), diethylene glycol monomethyl ether methacrylate (DEGMA), poly(ethylene
glycol) monomethyl ether methacrylate (PEGMA), and lauryl methacrylate (LMA) could successfully be
polymerized into homopolymers and diblock copolymers with good control over molecular weight, very high
conversions, and narrow molecular weight distributions. Polymers derived from the PFP-CTA possessed an
activated ester at the R-end of the polymer chain, which could be reacted with amines with high conversions.
The terminal É-dithioester group of each polymer chain could quantitatively be removed by treating the polymer
with an excess of AIBN, leaving the R-PFP ester functionality intact. Accordingly, the pentafluorophenyl ester
diazo compound could successfully be employed to functionalize RAFT polymers with a PFP ester at their É-end.
As a consequence, functionalization of both end groups was possible and led to telechelic polymers, exhibiting
an active ester at both ends of the polymer chain. As an example, a high molecular weight PMMA was prepared
by polycondensation with ethylenediamine
Quek JY, Zhu Y, Roth PJ, Davis TP, Lowe AB (2013) RAFT Synthesis and Aqueous Solution Behavior of Novel pH- and Thermo-Responsive (Co)Polymers Derived from Reactive Poly(2-vinyl-4,4-dimethylazlactone) Scaffolds, MACROMOLECULES 46 (18) pp. 7290-7302 AMER CHEMICAL SOC
Roth PJ, Theato P (2008) Versatile synthesis of functional gold nanoparticles: Grafting polymers from and onto, CHEMISTRY OF MATERIALS 20 (4) pp. 1614-1621 AMER CHEMICAL SOC
Functionalized gold nanoparticles have been prepared in an organic solvent by a two-phase reduction method in ethyl acetate and water using bis(6-hydroxyhexyl) disul?de bis(2-bromoisobutyl) ester, bis(6-acetyloxyhexyl) disul?de, and bis(5-carboxypentyl) disul?de bis(penta?uorophenyl) ester as stabilizing ligands. This procedure features the advantages that no phase transfer agent was necessary during the preparation of the gold nanoparticles and that the reducing conditions were mild enough to utilize functional disul?de ligands. The obtained gold nanoparticles with typical sizes between 2 and 5 nm could be precipitated and redispersed without any irreversible aggregation. Using these nanoparticles the stimuli-responsive polymers poly(N-isopropylacrylamide) and poly(N-cyclopropylacrylamide) could be grafted from the surface. Also, the grafting of polymers onto gold nanoparticles could be demonstrated with nanoparticles featuring penta?uorophenyl ester groups. The reactive character of gold nanoparticles featuring a penta?uorophenyl ester groups on the surface could also be applied in the preparation of multilayers on the basis of covalent bonds between the gold nanoparticles and polyallylamine.
Pei Y, Noy J-M, Roth PJ, Lowe AB (2015) Soft Matter Nanoparticles with Reactive Coronal Pentafluorophenyl Methacrylate Residues via Non-Polar RAFT Dispersion Polymerization and Polymerization-Induced Self-Assembly, JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY 53 (20) pp. 2326-2335 WILEY-BLACKWELL
Roth PJ, Davis TP, Lowe AB (2012) UCST-driven self-assembly and crosslinking of diblock copolymer micelles, POLYMER CHEMISTRY 3 (8) pp. 2228-2235 ROYAL SOC CHEMISTRY
The upper critical solution temperature (UCST) behaviour of poly[oligo(ethylene glycol)
monomethylether methacrylate] (POEGMA) in 1-octanol was exploited to self-assemble and crosslink
micellar aggregates. Four diblock copolymers, POEGMA-block-poly(N-isopropylacrylamide)
(POEGMA-b-PNIPAM), POEGMA-b-poly(N,N-diethylacrylamide) (POEGMA-b-PDEAM), and
two examples of POEGMA-b-[PNIPAM-co-poly(pentafluorophenyl acrylate)] (POEGMA-b-
(PNIPAM-co-PPFPA)), containing different amounts of activated PFP esters, were found to reversibly
self-assemble into well-defined spherical micelles upon cooling in 1-octanol, as evidenced by dynamic
light scattering (DLS) and electron microscopy. Transition temperatures, measured by turbidity and
DLS, were around room temperature and the PNIPAM and PDEAM blocks did not significantly
influence the critical temperature of the POEGMA block compared to homo POEGMA. The
aggregates exhibited an inverted morphology compared to PNIPAM core?POEGMA shell micelles
accessible through a thermally triggered self-assembly in water exploiting the lower critical solution
temperature (LCST) behaviour of PNIPAM. Inverted micelles with PNIPAM-co-PPFPA coronae in
1-octanol were shell crosslinked using a diamine and subsequently transferred into water. This procedure
yielded cage-like structures with swollen POEGMA cores and crosslinked PNIPAM shells. The shells
reversibly collapsed onto the cores when heated above the LCST of PNIPAM, providing particles with
novel architecture and the potential to host and release guest molecules by a thermal trigger.
Roth PJ, Theato P (2010) End group functionalization of RAFT polymers using thiol-alkyl methanethiosulfonate click-like chemistry, Polymer Preprints 51 pp. 746-747 American Chemical Society
Zhu Y, Lowe AB, Roth PJ (2014) Postpolymerization synthesis of (bis)amide (co)polymers: Thermoresponsive behavior and self-association, POLYMER 55 (17) pp. 4425-4431 ELSEVIER SCI LTD
Roth PJ, Jochum FD, Zentel R, Theato P (2009) Synthesis of Hetero-Telechelic alpha,omega Bio-Functionalized Polymers, BIOMACROMOLECULES 11 (1) pp. 238-244 AMER CHEMICAL SOC
Reversible addition-fragmentation chain transfer (RAFT) polymerization was used to synthesize poly[diethylene
glycol monomethylether methacrylate] (PDEGMA) (Mn ) 6250 g/mol, PDI ) 1.14) with a pentafluorophenyl
(PFP) activated ester and a dithioester end group. The hormone thyroxin (T4) was quantitatively attached to the
PFP activated ester R end group via its amino group. The É-terminal dithioester was not harmed by this reaction
and was subsequently aminolyzed in the presence of N-biotinylaminoethyl methanethiosulfonate, yielding a polymer
with a thyroxin and a biotin end group with very high heterotelechelic functionality. The polymer was characterized
by 1
H, 13C, and 19F NMR, UV-vis, and IR spectroscopy and gel permeation chromatography. The thyroxin
transport protein prealbumin with two thyroxin binding sites and streptavidin, which has four biotin binding sites,
was conjugated using the biotarget labeled polymer, resulting in the formation of a protein-polymer network,
confirming the heterotelechelic nature of the polymer. Polymer-protein microgel formation was observed with
dynamic light scattering. To realize a directed protein assembly, prealbumin was immobilized onto a surface,
exposing one of its two thyroxin binding groups and thus allowing the conjugation with the thyroxin R end group
of the heterotelechelic polymer. The biotin É end group of the attached polymer layer enabled the subsequent
immobilization of streptavidin, yielding a defined multilayer system of two proteins connected with the synthetic
polymer (efficiency of streptavidin immobilization 81% based on prealbumin). Without the polymer, no streptavidin
immobilization occurred. The layer depositions were monitored by surface plasmon resonance. The synthetic
approach of combining PFP activated esters with functional MTS reagents presents a powerful method for obtaining
well-defined heterotelechelic (bio-) functionalized polymers.
Jochum FD, Roth PJ, Kessler D, Theato P (2010) Double Thermoresponsive Block Copolymers Featuring a Biotin End Group, BIOMACROMOLECULES 11 (9) pp. 2432-2439 AMER CHEMICAL SOC
A poly(oligo(ethylene glycol) monomethyl ether methacrylate)-block-poly(N-isopropyl methacrylamide) (POEGMAb-PNIPMAM)
block copolymer with a biotin end group on the PNIPMAM block as a biotarget was synthesized
as a model system for temperature-controlled polymer immobilization. The synthesis was based on RAFT
polymerization followed by postpolymerization modification of an activated ester precursor block and an exchange
of the dithioester end group within one step. NMR, differential scanning calorimetry (DSC), dynamic light scattering
(DLS), and turbidimetry measurements were performed to investigate the stimulus-responsive properties. The
double thermoresponsive POEGMA-b-PNIPMAM with biotin end group showed a temperature-dependent
multistage assembly behavior as it was completely soluble in water at temperatures below the LCST of both
blocks, formed micellar structures above the LCST of PNIPMAM but below the LCST of POEGMA, or precipitated
from solution above the LCST of both blocks. At room temperature, the polymer could be immobilized onto
a streptavidin surface via its biotin end group, as shown in surface plasmon resonance (SPR) experiments. At
50 °C, at which the block copolymer formed micelles trapping the biotin target within the PNIPMAM core, no
immobilization was observed, showing that the biological binding ability of the model could be controlled via
external stimuli.
Roth PJ, Theato P (2013) Thiol?Thiosulfonate Chemistry in Polymer Science: Simple Functionalization of Polymers via Disulfide Linkages, In: Lowe AB, Bowman CN (eds.), Thiol-X Chemistries in Polymer and Materials Science 4 pp. 76-94 Royal Society of Chemistry
Wiss KT, zur Borg L, Roth PJ, Theato P (2010) Combining RAFT polymerization and activated ester chemistry to a versatile tool for polymer conjugation, Polymer Preprints 51 pp. 318-318 American Chemical Society
Roth PJ, Kim K-S, Bae SH, Sohn B-H, Theato P, Zentel R (2009) Hetero-Telechelic Dye-Labeled Polymer for Nanoparticle Decoration, MACROMOLECULAR RAPID COMMUNICATIONS 30 (14) pp. 1274-1278 WILEY-V C H VERLAG GMBH
Woodfield PA, Zhu Y, Pei Y, Roth PJ (2014) Hydrophobically Modified Sulfobetaine Copolymers with Tunable Aqueous UCST through Postpolymerization Modification of Poly(pentafluorophenyl acrylate), MACROMOLECULES 47 (2) pp. 750-762 AMER CHEMICAL SOC
Roth PJ, Davis TP, Lowe AB (2012) Comparison between the LCST and UCST Transitions of Double Thermoresponsive Diblock Copolymers: Insights into the Behavior of POEGMA in Alcohols, MACROMOLECULES 45 (7) pp. 3221-3230 AMER CHEMICAL SOC
Doubly thermoresponsive polymers consisting
of a poly[oligo(ethylene glycol) methyl ether methacrylate]
(POEGMA) block displaying UCST behavior in alcohols and
a block of poly(N-isopropylacrylamide) (PNIPAM) or poly-
(N,N-diethylacrylamide) (PDEAM), each of which has an
LCST in water, were synthesized using RAFT polymerization
followed by simultaneous activated ester/amine and nucleophilic
thiol?ene postpolymerization conversions. Upon
heating aqueous solutions of POEGMA-b-PNIPAM, 1
NMR spectroscopy confirmed a sudden decrease of the
PNIPAM signals at the LCST, indicating dehydration and chain collapse. Dynamic light scattering (DLS) and turbidity
measurements observed the macroscopic phase separation of the PNIPAM block at the same temperature. In 2-propanol, 1
NMR spectroscopy showed a gradual decrease of the POEGMA signals over a range of more than 30 °C during its UCST
transition, indicating early stages of chain crumpling up to 20 °C above the macroscopic phase separation. The OEG side chains
were found to collapse onto the backbone starting at the ester linkages, indicating the most unfavorable enthalpic polymer?
solvent interactions occur adjacent to the ester group. Although the diblock copolymers displayed a strong concentrationdependent
cloud point, 1
H NMR spectroscopy revealed a concentration-independent desolvation, indicating the potential for
applications that are not based on phase separation but on changes of polymer conformation. The phase separation occurred
within a narrow temperature range of POEGMA-b-PDEAM into micellar structures with POEGMA cores in 1-octanol. Cooling to point was necessary to produce compact structures. Upon heating, the aggregates remained compact until redissolving entirely
within a range of 1 °C, making the UCST of POEGMA in alcohols a valuable tool for reversible self-assembly applications.
Roth PJ, Kessler D, Zentel R, Theato P (2009) Versatile omega-End Group Functionalization of RAFT Polymers Using Functional Methane Thiosulfonates, JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY 47 (12) pp. 3118-3130 JOHN WILEY & SONS INC
Wiss KT, Krishna OD, Roth PJ, Kiick KL, Theato P (2009) A Versatile Grafting-to Approach for the Bioconjugation of Polymers to Collagen-like Peptides Using an Activated Ester Chain Transfer Agent, MACROMOLECULES 42 (12) pp. 3860-3863 AMER CHEMICAL SOC
Roth PJ, Jochum FD, Theato P (2011) UCST-type behavior of poly[oligo(ethylene glycol) methyl ether methacrylate] (POEGMA) in aliphatic alcohols: solvent, co-solvent, molecular weight, and end group dependences, SOFT MATTER 7 (6) pp. 2484-2492 ROYAL SOC CHEMISTRY
Poly[oligo(ethylene glycol) methyl ether methacrylate] (POEGMA) is shown to possess insoluble?
soluble transitions (UCST-type phase behavior) in a large variety of aliphatic alcohols. Samples of
different molecular weights ranging from 5 kg mol1 to 23 kg mol1 prepared by the RAFT process and
featuring different end groups at each end were analyzed by cloud point measurements. Transitions
occurred sharply and were fully reversible. The UCST was found to increase with an increasing
molecular weight. Hydrophobic (alkyl chain) end groups were found to lower the critical temperature
in isopropanol, while rigid aromatic end groups raised the transition temperature. In ternary mixtures
of isopropanol/chloroform/POEGMA, the UCST decreased with an increasing chloroform
concentration, with 10 vol% of chloroform accounting for a 30 C drop. In mixtures of isopropanol/
hexane/POEGMA, the cloud point increased significantly only with hexane concentrations above 30
vol%, at which level a 2 C transition temperature increase was found. Addition of water to isopropanol
solutions had a strong effect, with 1 vol% of water causing a decrease of the transition temperature of
12.5 C. With an increasing chain length of the solvent, the cloud point increased, while a branching of
the hydrocarbon chains lowered the cloud point. Samples of 23 kg mol1 POEGMA were for instance
found to have cloud points of 22.0 C in ethanol, 35.7 C in isopentanol, and 75.4 C in dodecanol.
Roth PJ, Haase M, Basche T, Theato P, Zentel R (2010) Synthesis of Heterotelechelic alpha,omega Dye-Functionalized Polymer by the RAFT Process and Energy Transfer between the End Groups, MACROMOLECULES 43 (2) pp. 895-902 AMER CHEMICAL SOC
The synthesis of a vinyl polymer with two different fluorescent dye end groups using reversible
addition-fragmentation chain transfer (RAFT) polymerization is described. Use of a pentafluorophenyl
(PFP) activated ester chain transfer agent (CTA) provided a polymer with an R end group that was reactive
toward amines and a dithioester É end group. The R PFP ester was amidated with Oregon Green Cadaverin.
This did not harm the É dithioester, which was subsequently aminolyzed with an excess of n-propylamine in
the presence of Texas Red-2-sulfonamidoethyl methanethiosulfonate, resulting in a disulfide bond connecting
the second dye to the polymer chain. Excess dyes and side products were removed by thin layer
chromatography (TLC). Gel permeation chromatography (GPC) using a UV-vis detector could verify the
presence of each dye on the polymer chain and the absence of free dyes. The synthesis of the polymer by a
living radical technique and the mild complementary conjugation methods conducted after polymerization at
each end group allowed to introduce complex dye residues possessing high brightness and photostability. In
particular, fluorescent dyes capable of acting as donor and acceptor for electronic excitation energy transfer
were chosen. Time-resolved fluorescence measurements were used to determine the time constant of energy
transfer between the end groups of isolated polymer chains. Assuming a Forster-type process, an average end- ¬
to-end distance of 4.5 nm was calculated, which was in reasonable agreement with data obtained from light
Zhu Y, Quek JY, Lowe AB, Roth PJ (2013) Thermoresponsive (Co)polymers through Postpolymerization Modification of Poly(2-vinyl-4,4-dimethylaziactone), MACROMOLECULES 46 (16) pp. 6475-6484 AMER CHEMICAL SOC
Pei Y, Jarrett K, Garces LG, Saunders M, Croue J-P, Roth PJ, Buckley CE, Lowe AB (2016) Synthesis and characterisation of non-ionic AB-diblock nanoparticles prepared by RAFT dispersion polymerization with polymerization-induced self-assembly, RSC ADVANCES 6 (33) pp. 28130-28139 ROYAL SOC CHEMISTRY
Roth PJ (2014) Composing Well- Defi ned Stimulus- Responsive Materials Through Postpolymerization Modifi cation Reactions, MACROMOLECULAR CHEMISTRY AND PHYSICS 215 (9) pp. 825-838 WILEY-V C H VERLAG GMBH
Roth PJ, Wiss KT, Theato P (2012) Post-Polymerization Modification, In: Matyjaszewski K, Moller M (eds.), Polymer Science: A Comprehensive Reference 5; Polycondensation 12 pp. 247-267 Elsevier
The synthesis of functional polymers has been enriched dramatically by post-polymerization modifications. Even though it represents a synthetically very appealing approach, different synthetic concepts of organic reactions are utilized in polymer science for the synthesis of architecturally well-defined multifunctional polymers. The different classes of reactions that provide the synthetic polymer chemist with tools of unprecedented precision, thereby opening the doors for materials synthesis in an interdisciplinary world, will be summarized.
Chua GBH, Roth PJ, Duong HTT, Davis TP, Lowe AB (2012) Synthesis and Thermoresponsive Solution Properties of Poly[oligo(ethylene glycol) (meth)acrylamide]s: Biocompatible PEG Analogues, MACROMOLECULES 45 (3) pp. 1362-1374 AMER CHEMICAL SOC
A library of (meth)acrylamido (co)polymers
was prepared by reacting poly(pentafluorophenyl (meth)-
acrylate) with ±-amino, É-methoxy functionalized di(ethylene
glycol), tri(ethylene glycol), and poly(ethylene glycol) (PEG)-
350, PEG-750, and PEG-5k, in combination with hexylamine
or thyroxine. The resulting copolymers showed an improved
solubility in water (higher or absent LCST values) and in
alcohols (lower or absent UCST values) than the analogous
common series of poly[oligo(ethylene glycol) methyl ether
(meth)acrylates]. The polyacrylamido species showed a better
solubility than the corresponding polymethacrylamido derivatives of similar molecular weight with all polyacrylamides
investigated being water-soluble at temperatures exceeding 90.0 °C. Tunable thermosensitive behavior could be effected by the
incorporation of the hydrophobic hexylamide comonomer. Similarly, an acrylamido backbone with grafted oligo(propylene glycol
600) amides exhibited a sharp LCST-type transition around 22.0 °C. The UCST-type transitions of the (meth)acrylamido
homopolymers were evaluated in 2-propanol and 1-octanol and were found to increase with an increasing ethylene glycol side
chain length, but were essentially independent of the alcohol chain length with polymers exhibiting higher UCST transitions in
2-propanol vs 1-octanol. Cytotoxicity tests on MRC5 fibroblast cells of the di- and tri(ethylene glycol) methyl ether acrylamido
homopolymers revealed no toxicity up to concentrations of 10.0 g/L. By employing mixtures of di(ethylene glycol) methyl ether
amine and the prohormone thyroxine (T4), water-soluble copolymers containing varying amounts of T4 could be easily
synthesized. Because of enhanced solubility, low toxicity, and higher hydrolytic stability of amides versus ester linkages, activated
ester polymers in combination with amino-functionalized ethylene glycol based side chains are presented as a versatile platform
for highly soluble, biocompatible, bioconjugated materials.
Kristanti A, Batchelor R, Albuszis M, Yap J, Roth PJ (2015) Temperature-heavy metal- and temperature-anion/molecule-responsive systems based on PEG acrylate copolymers containing dipyridyl ligands, EUROPEAN POLYMER JOURNAL 69 pp. 499-509 PERGAMON-ELSEVIER SCIENCE LTD
Albuszis M, Roth PJ, Pauer W, Moritz H (2016) Two in One: Use of Azide Functionality for Controlled Photo-crosslinking and Click-modification of Polymer Microspheres, Polymer Chemistry 7 (34) pp. 5414-5425 Royal Society of Chemistry
Spherical, micrometer-sized, azide-functional particles were produced through dispersion copolymerization of styrene and vinylbenzyl azide (VBA, 1?100 wt-% of monomer feed) in ethanol in the presence of stabilizers. The obtained microspheres were characterized by SEM, disc centrifuge, FT-IR and NMR spectroscopy, elemental analysis, DSC, and TGA, had measured azide loadings of up to 5.58 mmol/g, and average diameters that decreased with increasing azide content from 2.8 to 0.8 ¼m. Microspheres were irradiated at a wavelength of 254 nm resulting in crosslinking based on azide-to-nitrene decomposition and subsequent C?H insertion and C=C addition reactions. The conversion of azide functionality was monitored by FT-IR spectroscopy, elemental analysis, and DSC and was found to roughly follow first-order kinetics with increased rates found for microspheres with lower azide contents. Photocrosslinking preserved shapes and size distributions and, above a crosslinking degree of 10%, prevented microsphere dissolution in good solvents. By controlling the irradiation time, the amount of azide consumed for photo-crosslinking could be precisely adjusted. Residual azide groups spared during the irradiation were shown to be amenable to highly efficient CuAAC click modification with a fluorescent dye, Rhodamine B propargyl ester. Given the demand for functional crosslinked microspheres and the inherent difficulties associated with common synthetic strategies in producing such materials, this methodology based on two orthogonal chemistries of the azide functionality provides simple access to well-defined microspheres with customizable degrees of crosslinking and functional group densities.
Noy Janina-Miriam, Friedrich Ann-Katrin, Batten Kyle, Bhebhe Mathamsanqa N., Busatto Nicolas Van Luc, Batchelor Rhiannon R., Kristanti Ariella, Pei Yiwen, Roth Peter (2017) Para-Fluoro Postpolymerization Chemistry of Poly(pentafluorobenzyl methacrylate): Modification with Amines, Thiols, and Carbonylthiolates, Macromolecules 50 (18) pp. 7028-7040 American Chemical Society
A methacrylic polymer undergoing highly efficient para-fluoro substitution reactions
is presented. A series of well-defined poly(2,3,4,5,6-pentafluorobenzyl methacrylate) (pPFBMA)
homopolymers with degrees of polymerization from 28 to 132 and Ð d 1.29 was prepared by the
RAFT process. pPFBMA samples were atactic (with triad tacticity apparent in 1H and 19F NMR
spectra) and soluble in most organic solvents. pPFBMA reacted quantitatively through parafluoro
substitution with a range of thiols (typically 1.1 equiv thiol, base, RT, of any observed side reactions. Para-fluoro substitution with different (thio)carbonylthio
reagents was possible and allowed for subsequent one-pot cleavage of dithioester pendent groups
with concurrent thia-Michael side group modification. Reactions with aliphatic amines (typically
2.5 equiv amine, 50?60 °C, overnight) resulted in complete substitution of the para-fluorides
without any observed ester cleavage reactions. However, for primary amines, H2NR, double
substitution reactions yielding tertiary (?C6F4)2NR amine bridges were observed, which were
absent with secondary amine reagents. No reactions were found for attempted modifications of
pPFBMA with bromide, iodide, methanethiosulfonate, or thiourea, indicating a highly selective
reactivity toward nucleophiles. The versatility of this reactive platform is demonstrated through
the synthesis of a pH-responsive polymer and novel thermoresponsive polymers: an
oligo(ethylene glycol)-functional species with an LCST in water and two zwitterionic polymers
with UCSTs in water and aqueous salt solution (NaCl concentration up to 178 mM).
Busatto Nicolas, Van Luc, Stolojan Vlad, Shaw M, Keddie Joseph, Roth Peter (2018) Reactive Polymorphic Nanoparticles: Preparation via Polymerization-induced Self-assembly and Post-synthesis Thiol?para-Fluoro Core Modification, Macromolecular Rapid Communications Wiley-VCH Verlag
The use of 2,3,4,5,6-pentafluorobenzyl methacrylate (PFBMA) as a core-forming monomer in ethanolic RAFT dispersion polymerization formulations is presented. Poly[poly(ethylene glycol) methyl ether methacrylate] (pPEGMA) macromolecular chain transfer agents were chain extended with PFBMA leading to nanoparticle formation via polymerization-induced self-assembly (PISA). pPEGMA-pPFBMA particles exhibited the full range of morphologies (spheres, worms, and vesicles) including pure and mixed phases. Worm phases formed gels that underwent a thermo-reversible degelation and morphological transition to spheres (or spheres and vesicles) upon heating. Post-synthesis, the pPFBMA cores were modified through thiol?para-fluoro substitution reactions in ethanol using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as the base. For monothiols, conversions were 64% (1-octanethiol) and 94% (benzyl mercaptan). Spherical and worm-shaped nano-objects were core cross-linked using 1,8-octanedithiol, which prevented their dissociation in non-selective solvents. For a temperature-responsive worm sample, cross-linking additionally resulted in the loss of the temperature-triggered morphological transition. The use of the reactive monomer PFBMA in PISA formulations presents a simple method to prepare well-defined nano-objects similar to those produced with non-reactive monomers (e.g. benzyl methacrylate) and to retain morphologies independent of solvent and temperature.
Polysulfobutylbetaine (SBB) (co)polymers, zwitterionic species bearing ammonium and sulfonate groups
separated by a butyl spacer in every repeat unit, were prepared through three different synthetic routes
and their aqueous solution behaviour was studied. Postpolymerization quaternization of poly[2-(dimethylamino)ethyl
methacrylate] with 1,4-butanesultone resulted in incomplete modification due to the low
reactivity of this alkylating agent. RAFT radical polymerization of SBB-functional (meth)acrylate monomers
and their copolymerization with a sulfopropylbetaine (SPB) methacrylate yielded well-defined (co)polymers
with low dispersities 1.13 d ?M d 1.23 at monomer conversions of 75?92%. For a series of SBB
methacrylate homopolymers with increasing degrees of polymerization from 66?186 measured upper
critical solution temperature (UCST) cloud points increased from 27?77 °C. Cloud points of statistical
SPB-SBB copolymers with similar degrees of polymerization, but varying molar compositions, increased
linearly with SBB content offering a simple means of UCST tuning. Additionally, novel SBB acrylamide
homo- and copolymers were prepared by postpolymerization modification of poly(pentafluorophenyl
acrylate) with an SBB-functional amine and in mixtures with benzylamine as a hydrophobic modifier. In all
cases, the SBB (co)polymers had significantly higher UCSTs than their more common SPB counterparts,
greatly extending the temperature range of tuneable UCST transitions and making the investigated SBB
(co)polymers advantageous for exploiting their ?smart? behaviour. In this respect, combining SBB functionality
with hydrophobic benzylacrylamide comonomers is presented as a simple means of increasing the
maximum salt concentration at which UCST behaviour (which shows an antipolyelectrolyte effect) can be
observed, enabling UCST transitions in aqueous solutions containing a physiological concentration (9 g
) of NaCl.
Bingham Nathaniel M., Roth Peter J. (2018) Degradable Vinyl Copolymers through Thiocarbonyl Addition?Ring-Opening (TARO) Polymerization, Chemical Communications (55) pp. 55-58 Royal Society of Chemistry
The radical copolymerization of the thionolactone
dibenzo[c,e]oxepane-5-thione with acrylates, acrylonitrile, and
N,N-dimethylacrylamide afforded copolymers containing a
controllable amount of backbone thioesters which could be
selectively cleaved. The process is compatible with RAFT
polymerization and promising for the development of advanced
degradable polymers.
Noy Janina-Miriam, Li Yuman, Smolan Willi, Roth Peter J. (2019) The Azide?para-Fluoro Substitution on Polymers: Multi-purpose Precursors for Efficient Sequential Postpolymerization Modification, Macromolecules 52 (8) pp. 3083-3091 American Chemical Society
The 2,3,4,5,6-pentafluorobenzyl group has become a popular reactive functionality in polymer chemistry because of its high susceptibility to para-fluoro substitution with thiols. Herein, it is demonstrated postpolymerization that the para-fluoride can be substituted using sodium azide and that the resulting 4-azido-2,3,5,6-tetrafluorobenzyl-functional polymers are versatile precursors for a multitude of onward modifications with click-like efficiencies. Quantitative azide?para-fluoro substitution was found for poly(2,3,4,5,6-pentafluorobenzyl methacrylate) and the related Passerini ester?amide (meth)acrylic (co)polymers when heated in DMF with sodium azide to 80 °C for 60?90 min. Conversely, the azidation of poly(2,3,4,5,6-pentafluorostyrene) under similar conditions resulted in ~90% substitution efficiency. Azide-functional (co-)polymers were thermally stable below 100 °C and were subsequently modified with (i) four different alkynes (CuBr, triethylamine, DMF, 55 °C, overnight) to give 1,4-substituted 1,2,3-triazoles in >95% conversions; (ii) potassium thioacetate (DMF, RT, 15 min) with quantitative amidation to the acetanilide derivative; and (iii) DL-dithiothreitol (methanol/DMF, RT, 90 min) resulting in complete reduction of the azides to primary amines, which were subsequently acylated with two different acyl chlorides. Products were characterized by 1H NMR, 19F NMR, and FT-IR spectroscopies, and size exclusion chromatography. Given their adaptability, perfluorophenylazides have large potential as multi-purpose intermediates in polymer and materials chemistry.