Thermoresponsive hyperbranched polymers via In Situ RAFT copolymerization of peg‐based monomethacrylate and dimethacrylate monomers

Here we report the preparation of PEG‐based thermoresponsive hyperbranched polymers via a facile in situ reversible addition‐fragmentation chain transfer (RAFT) copolymerization using bis(thiobenzoyl) disulphide to form 2‐cyanoprop‐2‐yl dithiobenzoate in situ. This novel one‐pot in situ RAFT approach was studied firstly using methyl methacrylate (MMA) monomer, then was used to prepare thermoresponsive hyperbranched polymers by copolymerization of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA, M_n = 475), poly(propylene glycol) methacrylate (PPGMA, M_n = 375) and up to 30 % of ethylene glycol dimethacrylate (EGDMA) as the branching agent. The resultant PEGMEMA‐PPGMA‐EGDMA copolymers from in situ RAFT were characterized by Gel Permeation Chromatography (GPC) and ¹H‐NMR analysis. The results confirmed the copolymers with multiple methacrylate groups and hyperbranched structure as well as RAFT functional residues. These water‐soluble copolymers with tailored compositions demonstrated tuneable lower critical solution temperature (LCST) from 22 °C to 32 °C. The phase transition temperature can be further altered by post functionalization via aminolysis of RAFT agent residues in polymer chains. Moreover, it was demonstrated by rheological studies and particle size measurements that these copolymers can form either micro‐ or macro photocrosslinked gels at suitable concentrations due to the presence of multiple methacrylate groups. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3751–3761     

Thermoresponsive hydrogel of poly(glycidyl methacrylate‐co‐N‐isopropylacrylamide) as a nanoreactor of gold nanoparticles

The synthesis of a thermoresponsive hydrogel of poly(glycidyl methacrylate‐co‐N‐isopropylacrylamide) (PGMA‐co‐PNIPAM) and its application as a nanoreactor of gold nanoparticles are studied. The thermoresponsive copolymer of PGMA‐co‐PNIPAM is first synthesized by the copolymerization of glycidyl methacrylate and N‐isopropylacrylamide using 2,2′‐azobis(isobutyronitrile) as an initiator in tetrahydrofuran at 70 °C and then crosslinked with diethylenetriamine to form a thermoresponsive hydrogel. The lower critical solution temperature (LCST) of the thermoresponsive hydrogel is about 50 °C. The hydrogel exists as 280‐nm spheres below the LCST. The diameter of the spherical hydrogel gradually decreases to a minimum constant of 113 nm when the temperature increases to 75 °C. The hydrogel can act as a nanoreactor of gold nanoparticles because of the coordination of nitrogen atoms of the crosslinker with gold ions, on which a hydrogel/gold nanocomposite is synthesized. The LCST of the resultant hydrogel/gold nanocomposite is similar to that of the hydrogel. The size of the resultant gold nanoparticles is about 15 nm. The hydrogel/gold nanocomposite can act as a smart and recyclable catalyst. At a temperature below the LCST, the thermoresponsive nanocomposite is a homogeneous and efficient catalyst, whereas at a temperature above the LCST, it becomes a heterogeneous one, and its catalytic activity greatly decreases. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2812–2819, 2007     

Temperature‐sensitive hyperbranched poly(glycidol)s with oligo(ethylene glycol) monoethers

Temperature‐dependent polymers are intelligent materials. In this study, biocompatible and temperature‐dependent hyperbranched poly(glycidol)s (HPGs) were synthesized and characterized. HPGs were succinylated then modified with the oligo(ethylene glycol) monoethers (OEG) for example methoxy di(ethylene glycol), methoxy tri(ethylene glycol), methoxy tetra(ethylene glycol), ethoxy di(ethylene glycol), ethoxy tri(ethylene glycol), and methoxy poly(ethylene glycol)s at different ratios. These polymers exhibited phase transitions at a specific temperature (the cloud point), depending on the composition of OEG. By tuning the composition of OEG in the polymer, thermosensitive polymers with cloud point near body temperature were produced. Endothermic peaks of these polymers were observed in the vicinity of the cloud point. It is suggested that at temperatures below the cloud point the polymers formed hydrophobic shells and became more hydrophobic at temperatures above the cloud point. Because they exhibited no cytotoxicity, these temperature‐sensitive polymers are useful for biomedical applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4047–4054, 2010     

Temperature responsive copolymers of N‐vinylcaprolactam and di(ethylene glycol) methyl ether methacrylate and their interactions with drugs

Poly(N‐vinylcaprolactam) (PVCL) and poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) are well known for their thermoresponsive behavior in aqueous solutions. Indeed, they display lower critical solution temperatures (LCST) in the physiological range, which makes them interesting for biomedical devices and use in drug delivery systems. Homopolymers of N‐vinylcaprolactam and di(ethylene glycol) methyl ether methacrylate as well as copolymers thereof were synthesized by solution and direct miniemulsion polymerizations. The cloud points of the copolymers in aqueous solution were investigated as a function of temperature, comonomer ratio, and in the presence of model pharmaceutical ingredients. By variation of the comonomer ratio, it was possible to control the cloud point temperature between 26 and 35 °C, which was found to be beneficial to attenuate the effect of the drugs that also altered the cloud points. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3308–3313     

Tuning amphiphilicity/temperature‐induced self‐assembly and in‐situ disulfide crosslinking of reduction‐responsive block copolymers

New poly(ethylene oxide)‐based block copolymers (ssBCs) with a random copolymer block consisting of a reduction‐responsive disulfide‐labeled methacrylate (HMssEt) and a thermoresponsive di(ethylene glycol)‐containing methacrylate (MEO₂MA) units were synthesized. The ratio of HMssEt/MEO₂MA units in the random P(MEO₂MA‐co‐HMssEt) copolymer block enables the characteristics of well‐defined ssBCs to be amphiphilic or thermoresponsive and double hydrophilic. Their amphiphilicity or temperature‐induced self‐assembly results in nanoaggregates with hydrophobic cores having different densities of pendant disulfide linkages. The effect of disulfide crosslinking density on morphological variation of disulfide‐crosslinked nanogels is investigated. In response to reductive reactions, the partial cleavage of pendant disulfide linkages in the hydrophobic cores converts the physically associated aggregates to disulfide‐crosslinked nanogels. The occurrence of in‐situ disulfide crosslinks provides colloidal stability upon dilution. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2057–2067     

Hierarchically organized micellization of thermoresponsive rod‐coil copolymers based on poly[oligo(ethylene glycol) methacrylate] and poly(ε‐caprolactone)

A series of amphiphilic triblock copolymers, poly[oligo(ethylene glycol) methacrylate]_x‐block‐poly(ε‐caprolactone)‐block‐poly[oligo(ethylene glycol) methacrylate]_x, POEGMA_Co(x), were synthesized. Formation of hydrophobic domains as cores of the micelles was studied by fluorescence spectroscopy. The critical micelle concentrations in aqueous solution were found to be in the range of circa 10^?6 M. A novel methodology by modulated temperature differential scanning calorimetry was developed to determine critical micelle temperature. A significant concentration dependence of cmt was found. Dynamic light scattering measurements showed a bidispersed size distribution. The micelles showed reversible dispersion/aggregation in response to temperature cycles with lower critical solution temperature between 75 and 85 °C. The interplay of the two hydrophobic and one thermoresponsive macromolecular chains offers the chance to more complex morphologies. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Biodegradable poly(carbonate‐ether)s with thermoresponsive feature at body temperature

Novel biodegradable poly(carbonate‐ether)s (PCEs) with lower critical solution temperature (LCST) at body temperature were synthesized by copolymerization of CO₂ and ethylene oxide (EO) under double metal cyanide (DMC) catalyst. The PCEs showed carbonate unit (CU) content of 1.0–42.4 mol % and molecular weight of 2.7–247 kg/mol, which exhibited reversible thermoresponsive feature in deionized water with LCST in a broad window from 21.5 to 84.1 °C. The LCST was highly sensitive to the CU content and the molecular weight of PCEs, and it showed a linear relation with CU content for PCEs with similar molecular weight. In particular, aqueous solution of PCE with a 26.0 mol % of CU showed an LCST around 36.1 °C, which was very close to the body temperature. Interestingly, it was found that the phase transition behavior changed with PCE concentration. For PCE with M_n of 2.7 kg/mol and CU content of 30.0 mol %, the LCST increased from 21.5 to 36.7 °C when the PCE concentration changed from 10 to 1 g/L. Dynamic light scattering indicated that the phase transition was possibly due to a coil‐to‐globule transition. The thermoresponsive biodegradable PCE with LCST at body temperature is promising for biomedical applications, especially for in vivo applications. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis and characterization of novel thermoresponsive‐co‐biodegradable hydrogels composed of N‐isopropylacrylamide,poly(L‐lactic acid), and dextran

A series of novel multifunctional hydrogels that combined the merits of both thermoresponsive and biodegradable polymeric materials were designed, synthesized, and characterized. The hydrogels were copolymeric networks composed of N‐isopropylacrylamide (NIPAAM) as a thermoresponsive component, poly(L‐lactic acid) (PLLA) as a hydrolytically degradable and hydrophobic component, and dextran as an enzymatically degradable and hydrophilic component. The chemical structures of the hydrogels were characterized by an attenuated total reflection–Fourier transform infrared spectroscopy (ATR–FTIR) technique. The hydrogels were thermoresponsive, showing a lower critical solution temperature (LCST) at approximately 32 °C, and their swelling properties strongly depended on temperature changes, the balance of the hydrophilic/hydrophobic components, and the degradation of the PLLA component. The degradation of the hydrogels caused by hydrolytic cleavage of ester bonds in the PLLA component was faster at 25 °C below the LCST than at 37 °C above the LCST, determined by the ATR–FTIR technique. Due to their multifunctional properties, the designed hydrogels show great potential for biomedical applications, including drug delivery and tissue engineering. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5054–5066, 2004     

Alternating copolymers with degradability and quantitatively controlled thermosensitivity

To combine temperature responsivity and degradability, novel alternating copolymers with polyester backbone and oligo(ethylene glycol) side chain were designed and prepared by alternating ring‐opening copolymerization of succinic anhydride (SA) and functional epoxide monomer(s). The epoxide monomer containing one ethylene glycol unit, 2‐((2‐methoxyethoxy)methyl)oxirane (MEMO), has displayed similar copolymerization activity to that containing two ethylene glycol units, 2‐((2‐(2‐methoxyethoxy)ethoxy)methyl)oxirane (ME₂MO), when copolymerized with SA. This feature led to the formation of alternating copolymers with statistical random distribution of MEMO/ME₂MO units along the backbone when mixed MEMO/ME₂MO comonomers were fed. These polyesters possess degradability and quantitatively controlled lower critical solution temperature (LCST; 18–50 °C) and T_g (?40 to ?31 °C) both in linear relations with MEMO/ME₂MO feed ratio. Fine control of LCST near body temperature is thus realized for the reported degradable and thermoresponsive polyesters, which have promising applications in biomedical fields. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Thermosensitive polymer brush‐supported 4‐N,N‐dialkylaminopyridine on silica particles as catalyst for hydrolysis of an activated ester in aqueous buffers: Comparison of activity with linear polymer‐supported version and effect of LCST transition

We report on the synthesis of a thermosensitive polymer brush‐supported 4‐N,N‐dialkylaminopyridine catalyst and the comparison of its catalytic activity with the corresponding linear polymer‐supported version in the hydrolysis of p‐nitrophenyl acetate (NPA) as well as the effect of lower critical solution temperature (LCST) transition on catalytic activity. The polymer brushes were synthesized from initiator‐functionalized silica particles by surface‐initiated atom transfer radical polymerization of methoxytri(ethylene glycol) methacrylate and 2‐(N‐methyl‐N‐(4‐pyridyl)amino)ethyl methacrylate in the presence of a free initiator. Dynamic light scattering studies showed that the onset temperatures of the LCST transition of polymer brushes in pH 7.52 and 7.82 buffers were 42 and 38 °C, respectively. Under the same reaction conditions, the net initial rate of the hydrolysis of NPA catalyzed by hairy particles was 70–80% of that catalyzed by the free copolymer at the temperature below the LCST of polymer brushes. With further increasing the temperature above the LCST, the plot of logarithm of net initial rate versus inverse temperature exhibited a shift for the reactions catalyzed by hairy particles and leveled off or decreased slightly in the case of using the free copolymer as catalyst, presumably because the structures of the aggregates of hairy particles and free copolymer chains were different. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2853–2870, 2009     

The effect of structure on the thermoresponsive nature of well‐defined poly(oligo(ethylene oxide) methacrylates) synthesized by ATRP

Statistical copolymers of di(ethylene glycol) methyl ether methacrylate (MEO₂MA) and tri(ethylene glycol) methyl ether methacrylate (MEO₃MA) were synthesized by atom transfer radical polymerization (ATRP) providing copolymers with controlled composition and molecular weights ranging from M_n = 8,300–56,500 with polydispersity indexes (M_w/M_n) between 1.19 and 1.28. The lower critical solution temperature (LCST) of the copolymers increased with the mole fraction of MEO₃MA in the copolymer over the range from 26 to 52 °C. The average hydrodynamic diameter, measured by dynamic light scattering, varied with temperature above the LCST. These two monomers were also block copolymerized by ATRP to form polymers with molecular weight of M_n = 30,000 and M_w/M_n from 1.12 to 1.21. The LCST of the block copolymers shifted toward the LCST of the major segment, as compared to the value measured for the statistical copolymers at the same composition. As temperature increased, micelles, consisting of aggregated PMEO₂MA cores and PMEO₃MA shell, were formed. The micelles aggregated upon further heating to precipitate as larger particles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 194–202, 2008     

Thermosensitive water‐soluble poly(ethylene glycol)‐based polythiophene graft copolymers

Diethyleneglycol methylethermethacrylate(MeO₂MA) and oligoethylene glycol methylethermethacrylate(OEGMA) are polymerized on polythiophene(PT) backbone to produce water‐soluble PT‐g‐PMeO₂MA(PTD) and PT‐g‐P(MeO₂MA‐co‐OEGMA)(PTDO) using atom transfer radical polymerization. They are characterized by ¹H NMR and GPC techniques. TEM micrographs indicate that PT‐chains self‐organize as nanospheres, and atomic force micrographs suggest that aggregated PT‐chains are present at the centre surrounded by dispersed PMeO₂MA fibers producing miceller‐type aggregates. Dynamic light scattering study indicates an initial decrease followed by sharp increase of Z‐average particle size of PTD with temperature for attaining lower critical solution temperature (LCST) at 20 °C. The LCST increases with OEGMA concentration in PTDO. The temperature dependent PL emission of PTD shows a minimum at 19 °C, followed by a sharp increase till 21 °C, and in the cooling cycle, it shows a complete reversibility. In the PTDO copolymers, the PL intensity shows the hike at progressively higher temperatures due to the increase of LCST with increasing OEGMA concentration. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Star‐shaped polymers having side chain poss groups for solid polymer electrolytes; synthesis,thermal behavior,dimensional stability,and ionic conductivity

A series of organic/inorganic hybrid star‐shaped polymers were synthesized by atom transfer radical polymerization using 3‐(3,5,7,9,11,13,15‐heptacyclohexyl‐pentacyclo[9.5.1.1^3,9.1^5,15.1^7,13]‐octasiloxane‐1‐yl)propyl methacrylate (MA‐POSS) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) as monomers and octakis(2‐bromo‐2‐methylpropionoxypropyldimethylsiloxy)octasilsesquioxane as an initiator. Star‐shaped polymers with methyl methacrylate (MMA) and PEGMA moieties were also prepared for comparison purposes. Dimensionally stable freestanding film could be obtained from the hybrid star‐shaped polymer containing 26 wt % of MA‐POSS moieties although its glass transition temperature is very low, ?60.9 °C. As a result, the hybrid star‐shaped polymer electrolyte containing lithium bis(trifluoromethanesulfonyl)imide showed ionic conductivities (1.75 × 10^?5 S/cm at 30 °C), which were two orders of magnitude higher than those of the star‐shaped polymer electrolyte with MMA moieties. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

One‐step synthesis of hyperbranched polyethylene macroinitiator and its block copolymers with methyl methacrylate or styrene via ATRP

Block copolymers of hyperbranched polyethylene (PE) and linear polystyrene (PS) or poly(methyl methacrylate) (PMMA) were synthesized via atom transfer radical polymerization (ATRP) with hyperbranched PE macroinitiators. The PE macroinitiators were synthesized through a “living” polymerization of ethylene catalyzed with a Pd‐diimine catalyst and end‐capped with 4‐chloromethyl styrene as a chain quenching agent in one step. The macroinitiator and block copolymer samples were characterized by gel permeation chromatography, ¹H and ¹³C NMR, and differential scanning calorimetry. The hyperbranched PE chains had narrow molecular weight distribution and contained a single terminal benzyl chloride per chain. Both hyperbranched PE and linear PS or PMMA blocks had well‐controlled molecular weights. Slow initiation was observed in ATRP because of steric effect of hyperbranched structures, resulting in slightly broad polydispersity index in the block copolymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3024–3032, 2010     

Synthesis,self‐assembly,and thermosensitivity of amphiphilic POEGMA‐PDMS‐POEGMA triblock copolymers

In this article, the synthesis and self‐assembly of a novel well‐defined biocompatible amphiphilic POEGMA‐PDMS‐POEGMA triblock copolymer were studied. The copolymer was synthesized by atom transfer radical polymerization of oligo(ethylene glycol) methyl ether methacrylate (OEGMA) using α,ω‐dibromo polydimethylsiloxane macroinitiator (Br‐PDMS‐Br). Br‐PDMS‐Br was synthesized through the esterification of α,ω‐hydroxypropyl polydimethylsiloxane and 2‐bromoisobutyryl bromide. The structures of the copolymers were confirmed by proton nuclear magnetic resonance spectroscopy, and gel permeation chromatography. The copolymers showed reversible aggregation in response to temperature cycles with a lower critical solution temperature (LCST) between 61 and 66 °C, as determined by ultraviolet‐visible spectrophotometry and dynamic light scattering. The LCST values increased in proportion to the length of the hydrophilic block and were lower than that of the POEGMA homopolymer. The self‐assembly behavior of the copolymers in aqueous solution was investigated by fluorescence spectroscopy and transmission electron microscopy. The critical micelle concentration value (1.08–0.26 10^?6 mol L^?1) decreased as the length of the POEGMA chain increased. The POEGMA‐PDMS‐POEGMA copolymers can easily self‐assemble into spherical micelles in aqueous solution. Such biocompatible block copolymers may be attractive candidates as ‘‘smart'' thermo‐responsive drug delivery systems. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2684‐2691     

Synthesis,self‐assembly,fluorescence, and thermosensitive properties of star‐shaped amphiphilic copolymers with porphyrin core

Star‐shaped amphiphilic poly(ε‐caprolactone)‐block‐poly(oligo(ethylene glycol) methyl ether methacrylate) with porphyrin core (SPPCL‐b‐POEGMA) was synthesized by combination of ring‐opening polymerization (ROP) and atom transfer radical polymerization (ATRP). Star‐shaped PCL with porphyrin core (SPPCL) was prepared by bulk polymerization of ε‐caprolactone (CL) with tetrahydroxyethyl‐terminated porphyrin initiator and tin 2‐ethylexanote (Sn(Oct)₂) catalyst. SPPCL was converted into SPPCLBr macroinitiator with 2‐bromoisobutyryl bromide. Star‐shaped SPPCL‐b‐POEGMA was obtained via ATRP of oligo(ethylene glycol) methyl ether methacrylate (OEGMA). SPPCL‐b‐POEGMA can easily self‐assemble into micelles in aqueous solution via dialysis method. The formation of micellar aggregates were confirmed by critical micelle formation concentration, dynamic light scattering, and transmission electron microscopy. The micelles also exhibit property of temperature‐induced drug release and the lower critical solution temperature (LCST) was 60.6 °C. Furthermore, SPPCL‐b‐POEGMA micelles can reversibly swell and shrink in response to external temperature. In addition, SPPCL‐b‐POEGMA can present obvious fluorescence. Finally, the controlled drug release of copolymer micelles can be achieved by the change of temperatures. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Design and synthesis of fluorescent core–shell nanoparticles with tunable lower critical solution temperature behavior and metal‐enhanced fluorescence

In this article, the preparation of fluorescent nanohybrids with core–shell structure and metal‐enhanced fluorescence (MEF) effect was presented. The fluorescent core–shell nanohybrids were prepared using silver nanoparticles (AgNPs) as cores and fluorophore tethered thermoresponsive copolymers with tunable lower critical solution temperature (LCST) from 15 to 90 °C as shells. These thermoresponsive copolymers were synthesized by the random copolymerization of oligo(ethylene oxide) acrylate and di(ethylene oxide) ethyl ether acrylate using reversible addition–fragmentation chain transfer polymerization and grafted on to AgNPs surface via Ag–S coordination interaction. By thermal manipulation of polymer spacer between AgNPs and fluorophores, the tunable MEF was achieved. It was also revealed that the fluorescent nanohybrids would exhibit maximal MEF when the polymerization degree was tuned to 350. The manipulation of the solution temperatures below and above LCST resulted in switchable MEF behavior. In addition, the phase transition process of the thermoresponsive copolymer was also studied by MEF effect using this fluorescent core–shell nanohybrid design. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 87–95     

Temperature‐induced phase transition of poly(N‐n‐propylacrylamide‐co‐butyl methacrylate‐co‐N,N‐diethylaminoethyl methacrylate)

Terpolymers composed of N‐n‐propylacrylamide (NPAAm), butyl methacrylate (BMA), and N,N‐diethylaminoethyl methacrylate (DEAEMA) were prepared in an attempt to investigate the temperature‐induced phase transition and its mechanism. Poly(NPAAm) showed the lower critical solution temperature (LCST) around 24°C in water. With the incorporation of DEAEMA with NPAAm, the LCST change was characterized by an initial increase. However, the LCST was shifted to the lower temperature at the later stage. This might be explained in terms of hydrophilic/hydrophobic contribution of DEAEMA to the LCST. The swelling behavior of copolymer gel in the various solvents and spin‐lattice relaxation time (T₁) study by NMR strongly suggested the hydrophilic/hydrophobic contribution of DEAEMA to the LCST depending on the local environment. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1407–1411, 1999     

Amphiphilic conetworks. III. Poly(2,3‐dihydroxypropyl methacrylate)–polyisobutylene and poly(ethylene glycol) methacrylate–polyisobutylene based hydrogels prepared by two‐step polymer procedure

This article describes the synthesis and characterization of new amphiphilic polymer conetworks containing hydrophilic poly(2,3‐dihydroxypropyl methacrylate) or poly(ethylene glycol) methacrylate (PEGMA) and hydrophobic polyisobutylene chains. This conetworks were prepared by a two‐step polymer synthesis. In the first step, a cationic copolymer of isobutylene and 3‐isopropenyl‐α,α‐dimethylbenzyl isocyanate (IDI) was prepared. The isocyanate groups of the IB‐IDI random copolymer were subsequently transformed in situ to methacrylate (MA) groups in reaction with 2‐hydroxyethyl methacrylate (HEMA). In the second step, the resulting MA‐multifunctional PIB‐based crosslinker, PIB(MA)_n, with an average functionality of approximately four per chain, was copolymerized with 2,3‐dihydroxypropyl methacrylate or poly(ethylene glycol) methacrylate by radical mechanism in tetrahydrofuran giving rise to amphiphilic conetworks containing 11–60 mol % of DHPMA or 10–12 mol % of PEGMA. The synthesized conetworks were characterized with solid‐state ¹³C‐NMR spectroscopy and differential scanning calorimetry. The amphiphilic nature of the conetworks was proved by swelling in both water and n‐heptane. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4074–4081, 2007     

Controlled metal‐free polymerization toward well‐defined thermoresponsive polypeptides by polymerization at low temperature

A controlled metal‐free synthetic methodology toward well‐defined thermoresponsive polypeptides by decreasing the reaction temperature to 0 °C has been developed. Good control over the molecular weight in the polymerization of a trithiocarbonate‐functionalized N‐carboxyanhydride (MES‐l ‐Glu‐NCA) monomer was obtained using n‐hexylamine as the initiator at 0 °C. It yielded homopolypeptide macro‐transfer agent (PMESLG) with narrow molecular weight distribution (PDI < 1.3) and controllable chain length. Detailed ¹H NMR and MALDI‐TOF‐MS analysis clearly confirmed that frequently occurring side‐reactions was absent at 0 °C, and the polymerization was controlled. The resultant PMESLG was applied to mediate the reversible addition‐fragmentation chain transfer (RAFT) polymerization of oligo‐ethylene‐glycol acrylate (OEGA) for the metal‐free synthesis of thermoresponsive polypeptides. These thermoresponsive polypeptides have well‐controlled molecular weight, adopted regular α‐helical conformation, and exhibited a lower critical solution temperature between 23 °C and 55 °C. To the best of our knowledge, there are very few reports about the synthesis of well‐defined thermoresponsive graft polypeptides via NCA polymerization and RAFT. Consequently, this provides a new strategy for the synthesis of promising intelligent material for future biomedical applications. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2618–2624