Graft polymerization of vinyl monomers inside macroporous polyacrylamide gel,cryogel, in aqueous and aqueous‐organic media initiated by diperiodatocuprate(III) complexes

Graft polymerization initiated by diperiodatocuprate(III) complex (Cu(III)) initiator was found to be an effective and convenient method for graft polymerization of vinyl monomers onto macroporous polyacrylamide gels, the so‐called cryogels (pAAm‐cryogels). The effect of time, temperature, monomer and initiator concentration during the graft polymerization in aqueous and aqueous‐organic media was studied. The graft polymerization of water‐soluble monomers as [2‐(methacryloyloxy)ethyl]‐trimethylammonium chloride, 2‐hydroxyethyl methacrylate, N‐isopropylacrylamide, and N,N‐dimethylacrylamide proceeds with higher grafting yield in aqueous medium, as compared with that in aqueous‐organic media. Graft polymerization in aqueous‐organic media such as water–DMSO solutions allows grafting of water‐insoluble monomers such as glycidyl methacrylate and N‐tert‐butylacrylamide with high grafting degrees of 100 and 410%, respectively. It was found that the deposition of initiator on the pore surface of cryogels promoted graft polymerization by facilitating the formation of the redox couple Cu(III)‐acrylamide group. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1952–1963, 2006     

RAFT cryopolymerizations of N,N‐dimethylacrylamide and N‐isopropylacrylamide in moderately frozen aqueous solution

Aqueous reversible addition‐fragmentation chain transfer (RAFT) cryopolymerizations of N,N‐dimethylacrylamide (DMA) and N‐isopropylacrylamide (NIPAM) with potassium persulfate/sodium ascorbate as redox initiators were performed at ?15 °C. For the homopolymerizations, water‐soluble chain transfer agents (CTAs) of 2‐(1‐carboxy‐1‐methylethyl‐sulfanylthiocarbonylsulfanyl)‐2‐methylpropionic acid and 2‐dodecylsulfanylthiocarbonylsulfanyl‐2‐methylpropionyl‐capped methoxy poly(ethylene glycol) were used. For the sequential block copolymerizations, the obtained trithiocarbonate‐functionalized polymers were used as macro‐CTAs. Although well‐defined homo and block polymers of DMA and NIPAM were synthesized and these RAFT cryopolymerizations were well controlled, their behavior depended on the monomers and CTAs. The polymerization kinetic and polymer structure were studied by proton nuclear magnetic resonance analysis and gel permeation chromatography measurement. Poly(N,N‐dimethylacrylamide)‐based cryogels crosslinked with reductively cleavable disulfide‐containing diacrylamide, N,N′‐bisacryloylcystamine, were synthesized via RAFT cryopolymerization. Scanning electron microscopy observation revealed that the porous structure of cryogels depended on the CTA used. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

Microwave‐assisted nitroxide‐mediated polymerization for water‐soluble homopolymers and block copolymers synthesis in homogeneous aqueous solution

We performed a critical reinvestigation of microwave enhancement of nitroxide‐mediated polymerization (NMP) of acrylamide (AM) in aqueous media in the dynamic (DYN) mode with a combination of a conventional hydrosoluble radical initiator and a β‐phosphonylated nitroxide (SG1). Based on the results of our previous work, a complementary series of polymerization reactions was carried out between 130 and 160 °C using only the DYN mode to ascertain the existence of a microwave effect. The polymer conversion (p), molar masses, polydispersity index, and viscosity of each sample were measured. The temperature was monitored inside and outside of the vessel using an optical fiber sensor and an IR sensor, respectively. Microwave enhancement of polymerization, temperature control and viscosity of the reaction media were closely related. We also furthered the field of hydrophilic AB diblock copolymer synthesis using a tertiary SG1‐based macroalkoxyamine and directly synthesized both poly(acrylamide‐b‐sodium 2‐acrylamido‐2‐methylpropanesulfonate), a neutral‐b‐anionic diblock copolymer, and poly(acrylamide‐b‐3‐dimethyl(methacrylamidopropyl)ammonium propanesulfonate), a neutral‐b‐zwitterionic diblock copolymer, in homogeneous aqueous media. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Room‐temperature RAFT copolymerization of 2‐chloroallyl azide with methyl acrylate and versatile applications of the azide copolymers

A new vinyl azide monomer, 2‐chlorallyl azide (CAA), has been synthesized from commercially available reagent in one step. The reversible addition fragmentation chain transfer (RAFT) copolymerization of CAA with methyl acrylate (MA) was carried out at room temperature using a redox initiator, benzoyl peroxide (BPO)/N,N‐dimethylaniline (DMA), in the presence of benzyl 1H‐imidazole‐1‐carbodithioate (BICDT). The polymerization results showed that the process bears the characteristics of controlled/living radical polymerizations, such as the molecular weight increasing linearly with the monomer conversion, the molecular weight distribution being narrow, and a linear relationship existing between ln([M]₀/[M]) and the polymerization time. Chain extension polymerization was performed successfully to prepare block copolymer. Furthermore, the azide copolymers were functionalized by Cu^I‐catalyzed “click” reaction with alkyne‐containing poly(ethylene glycol) (PEG) to yield graft copolymers with hydrophilic PEG side chains. Surface modification of the glass sheet was successfully achieved via the crosslinking reaction of the azide copolymer under UV irradiation at ambient temperature. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1348–1356, 2010     

High molecular weight polyacrylamides by atom transfer radical polymerization: Enabling advancements in water‐based applications

Through the use of copper (I) chloride (CuCl) and tris(2‐dimethylaminoethyl)amine (Me₆‐TREN) as a metal/ligand pair, conditions for the robust, fast, and controlled radical polymerization of high molecular weight N‐hydroxyethylacrylamide (HEAm),N‐isopropylacrylamide (NIPAm), N,N′‐dimethylacrylamide (DMAm), and acrylamide (Am) at ambient temperature are reported. Linear evolution of molecular weight and narrow molecular weight distribution was observed for all monomers with degrees of polymerization ranging from 50 to 5000. Random copolymers of several acrylamide‐based monomers are also reported with excellent control over molecular weight and polydispersity. Characterization of high molecular weight poly (NIPAm) demonstrated large changes in the lower critical solution temperature observed on heating and cooling, and this hysteresis was exploited for the controlled release of doxorubicin from poly(NIPAm) spheres. This study represents the first example of preparation of high molecular weight acrylamide polymers by a metal‐mediated controlled radical polymerization technique. Access to these materials, as well as to NIPAm polymers in particular, opens new doors for interesting applications in a variety of fields including tissue engineering, drug delivery, and controlled solution viscosity. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Aqueous MADIX/RAFT polymerization of diallyldimethylammonium chloride: Extension to the synthesis of poly(DADMAC)‐based double hydrophilic block copolymers

Macromolecular design by interchange of xanthates/reversible addition fragmentation chain transfer polymerization (MADIX/RAFT) of diallyldimethylammonium chloride (DADMAC) using the hydrophobic O‐ethyl‐S‐(1‐methoxycarbonyl) ethyl dithiocarbonate MADIX/RAFT mediating agent, Rhodixan A1, was investigated. Attempts to obtain an efficient control of DADMAC polymerization in a water/ethanol mixture failed because of significant chain transfer to ethanol. The use of a water‐soluble Rhodixan A1‐terminated acrylamide oligomer as the MADIX/RAFT agent enabled the controlled polymerization of DADMAC in water at 50 °C using the cationic azo initiator V‐50. An excellent agreement was found between experimental and theoretical M_n values throughout polymerization and over a broad range of initial concentration of xanthate. Polydispersity indexes (PDIs) at the end of the polymerization were abnormally high for a process showing a linear increase of M_n with monomer conversion (1.8 < PDI < 2.0). This feature was explained by the measurement of a high transfer constant to xanthate (C_x = 18.8 ± 1.6) but a low interchange transfer constant (C_ex = 1.5). Nevertheless, poly(acrylamide)–poly(DADMAC) double hydrophilic block copolymers (DHBCs) of controlled M_n and composition could be successfully synthesized for the first time. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Novel thermoresponsive fluorinated double‐hydrophilic poly{[N‐(2,2‐difluoroethyl)acrylamide]‐b‐[N‐(2‐fluoroethyl)acrylamide]} block copolymers

Novel thermoresponsive double‐hydrophilic fluorinated block copolymers were successfully synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization. Poly[N‐(2,2‐difluoroethyl)acrylamide] (P2F) was synthesized via RAFT polymerization of N‐(2,2‐difluoroethyl)acrylamide (M2F) using 2‐dodecylsulfanylthiocarbonylsulfanyl‐2‐methylpropionic acid (DMP) as the chain transfer agent (CTA) and 2,2′‐azobisisobutyronitrile (AIBN) as the initiator. The resulting P2F macroCTA was further chain extended with N‐(2‐fluoroethyl)acrylamide (M1F) to yield poly{[N‐(2,2‐difluoroethyl)acrylamide]‐b‐[N‐(2‐fluoroethyl)acrylamide]} (P2F‐b‐P1F) block copolymers with different lengths of the P1F block. Molecular weight and molecular weight distribution were determined by gel permeation chromatography. The average molecular weight (M_n) of the resulting polymers ranged from 2.9 × 10⁴ to 5.8 × 10⁴ depending on the length of the P1F block. The molecular weight distribution was low (M_w/M_n = 1.11–1.19). Turbidimetry by UV‐Visble (UV‐Vis) spectroscopy, dynamic light scattering, and in situ temperature‐dependent ¹H NMR measurements demonstrated that the P2F block underwent a thermal transition from hydrophilic to hydrophobic, which in turn induced self‐assembly from unimers to aggregates. Transmission electron microscopy studies demonstrated that polymeric aggregates formed from an aqueous solution of P2F‐b‐P1F at 60 °C were disrupted by cooling down to 20 °C and regenerated by heating to 60 °C. Temperature‐triggered release of a model hydrophobic drug, coumarin 102, was also demonstrated. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

“On–off” switching of dynamically controllable self‐assembly formation of double‐responsive block copolymers with tunable LCSTs

We report here a reversible self‐assembly formation system using block copolymers with thermo‐tunable properties. A series of double‐responsive block copolymers, poly(N‐isopropylacrylamide (NIPAAm))‐block‐poly(NIPAAm‐co‐N‐(isobutoxymethyl)acrylamide (BMAAm)) with two lower critical solution temperatures were synthesized by one‐pot atom transfer radical polymerization via sequential monomer addition. When dissolved in aqueous solution at room temperature, the block copolymers remained unimeric. Upon heating above room temperature, the block copolymers self‐assembled into micellar structures. The micelle formation temperature and the resulting diameter were controlled by varying the BMAAm content. ¹H Nuclear Magnetic Resonance, dynamic light scattering, field‐emission scanning electron microscopy, and fluorescence spectra revealed the presence of a monodisperse nanoassembly, and demonstrated the assembly formation/inversion process was fully reversible. Moreover, a model hydrophobic molecule, pyrene, was successfully loaded into the micelle core by including pyrene in the original polymer solution. Further heating resulted in mesoscopic micelle aggregation and precipitation. This dual micelle and aggregation system will find utility in drug delivery applications as a thermal trigger permits both aqueous loading of hydrophobic drugs and their subsequent release. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

A combining signal amplification of atom transfer radical polymerization and redox polymerization for visual biomolecules detection

A novel combination of atom transfer radical polymerization (ATRP) and redox polymerization is here used to allow instrument‐free visualization of special biomolecules for which dynamic polymer growth is used in signal amplification. In this method, the convenient and mild redox polymerization‐assisted amplification with cerium ammonium (IV) nitrate as oxidant at the second stage was achieved by directly using the hydroxyl groups from poly(hydroxyethyl methacrylate) (PHEMA) synthesized via ATRP at the first stage. The brushed polymers poly(hydroxylethyl methacrylate)‐branched‐poly (acrylamide) (PHEMA‐branched‐PAM) prepared by successive ATRP and redox polymerization in situ drastically grew up at the detected biomolecules spot to improve the visibility of biomolecule and simplify the detection procedure. With the proposed strategy, the signal amplification of streptavidin (SA) as model detected biomolecule was investigated on two different substrates such as silicon wafer and gold, respectively. As a result, detection limit of SA was demonstrated on the gold substrates where binding of 1.0 ng/mL SA was differentiable from the background using ellipsometry. Moreover, binding of 0.5 nmol/L DNA led to visually distinguishable spots on the gold surface under mild condition. The proposed method exhibited an efficient amplification performance for molecules detection, and paved a new way for visual diagnosis of biomolecules. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2791–2799     

Facile synthesis of N‐vinylimidazole‐based hydrogels via frontal polymerization and investigation of their performance on adsorption of copper ions

We report a new facile strategy for quickly synthesizing pH sensitive poly(VI‐co‐HEA) hydrogels (VI = N‐vinylimidazole; HEA = 2‐hydroxyethyl acrylate) by frontal polymerization. The appropriate amounts of VI, HEA, and ammonium persulfate (APS)/N,N,N′,N′‐tetramethylethylenediamine (TMEDA) couple redox initiator were mixed together at ambient temperature in the presence of glycerol as the solvent medium. Frontal polymerization (FP) was initiated by heating the upper side of the mixture with a soldering iron. Once initiated, no further energy was required for the polymerization to occur. The dependence of the front velocity and front temperature on the VI/HEA weight ratios were investigated. The pH sensitive behavior, morphology, and heavy metal removal study of poly(VI‐co‐HEA) hydrogels prepared via FP were comparatively investigated on the basis of swelling measurements, scanning electron microscopy, and inductively coupling plasma spectrometer. Results show that the poly(VI‐co‐HEA) hydrogels prepared via FP exhibit good pH sensitivity and adsorption capacity. The FP can be exploited as an alternative means for synthesis of pH sensitive hydrogels in a fast and efficient way. The as‐prepared hydrogels can be applied to remove heavy metals. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4005–4012, 2010     

Redox initiated cationic polymerization: Silane‐N‐aryl heteroaromatic onium salt redox couples

In this article, a new route for the synthesis of N‐aryl heteroaromatic onium salts by the direct copper catalyzed arylation of pyridine, substituted pyridines, isoquinoline, and acridine with diaryliodonium salts is described. It was demonstrated that these N‐aryl heteroaromatic onium salts undergo facile platinum or rhodium‐catalyzed reduction by silanes bearing Si? H groups. The reduction of N‐aryl heteroaromatic onium salts generates Brønsted acids. When this redox reaction was carried out in situ in the presence of an appropriate monomer, cationic polymerization was observed. Using this approach, the cationic polymerizations of epoxides, oxetanes, 1,3,5‐trioxane, styrene, and vinyl ethers were carried out. The use of optical pyrometry to monitor the redox initiated cationic polymerizations of some representative multifunctional monomers is described. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis of comb‐branched polyacrylamide with cationic poly[(2‐dimethylamino)ethyl methacrylate dimethylsulfate] quat

Comb‐branched polyelectrolytes with polyacrylamide backbones and poly[(2‐dimethylamino)ethyl methacrylate methylsulfate] (polyDMAEMA‐DMS) side chains were prepared by free‐radical macromonomer polymerization. PolyDMAEMA‐DMS macromonomers bearing terminal styrenic moieties were synthesized by living anionic polymerization with lithium 4‐vinylbenzylamide (LiVBA) and lithium N‐isopropyl‐4‐vinylbenzylamide (LiPVBA) as initiators. In the presence of LiCl, LiPVBA initiated a living polymerization of 2‐(dimethylamino)ethyl methacrylate (DMAEMA) and produced polymers with well‐controlled molecular weights and low polydispersities. LiVBA could not directly initiate DMAEMA polymerization. After being capped with two units of dimethylacrylamide, DMAEMA polymerized with an initiator efficiency of 63%. The quaternization of the poly[(2‐dimethylamino)ethyl methacrylate] macromonomer with dimethyl sulfate yielded the cationic polyDMAEMA‐DMS macromonomer. The polyDMAEMA‐DMS macromonomer had a much higher reactivity than acrylamide in free‐radical polymerization. This might have been due to the formation of polyDMAEMA‐DMS micelles in the polymerization system. The high macromonomer reactivity caused composition drift in a batch process. A semibatch method with a constant polyDMAEMA‐DMS feed rate was used to control the copolymer composition. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2394–2405, 2002     

Syntheses and polymerizations of novel chiral poly(acrylamide) macromonomers and their chiral recognition abilities

Chiral poly(acrylamide) macromonomers (PMB‐1, PMB‐2, PPAE‐1, and PPAE‐2) were synthesized from 2‐methacryloyloxyethyl isocyanate and prepolymers, that is, poly[(S)‐methylbenzyl acrylamide] or poly(L ‐phenylalanine ethylester acrylamide with a terminal carboxylic acid or hydroxy group. Radical homopolymerizations of poly(acrylamide) macromonomers were carried out under several conditions to obtain the corresponding optically active polymers. A strong temperature dependence on the specific optical rotation was observed for poly(PPAE‐2) in comparison with that for the corresponding prepolymer. This might have resulted from a change in the conformation caused by hydrogen bonds between polymer‐graft branches in the polymacromonomer. Radical copolymerizations of poly(acrylamide) macromonomers with styrene and methyl methacrylate were performed with azobisisobutyronitrile in tetrahydrofuran at 60 °C. Chiroptical properties of the copolymers were slightly influenced by comonomer units. Chiral stationary phases were prepared by the radical polymerization of poly(acrylamide) macromonomers in the presence of silica gel containing vinyl groups on the surface. Some racemic compounds such as menthol and mandelic acid were resolved on the chiral stationary phases for high‐performance liquid chromatography. The conformation based on hydrogen bonds between polymer‐graft branches in the polymacromonomers may play an important role in chiral discrimination. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1726–1741, 2002     

Semi‐interpenetrating polymer networks based on crosslinked poly(N‐isopropyl acrylamide) and methylcellulose prepared by frontal polymerization

In this work, semi‐interpenetrating gels of poly(N‐isopropyl acrylamide) and methylcellulose were successfully synthesized by using the Frontal Polymerization (FP) technique. The gels were obtained in the presence of dimethyl sulfoxide and trihexyltetradecylphosphonium persulfate, as polymerization solvent and radical initiator, respectively, hence avoiding the formation of bubbles during polymerization. Then, some of the gels containing dimethyl sulfoxide were thoroughly washed with water, hence obtaining the corresponding hydrogels. The effects of the ratio between poly(N‐isopropyl acrylamide) and methylcellulose, the amount of crosslinker and solvent medium (i.e., dimethyl sulfoxide and water) were thoroughly studied, assessing the influence of temperature and velocity of FP fronts on the glass transition temperature values (dried samples), on the swelling behavior and on the dynamic‐mechanical properties (gels swollen both in water and dimethyl sulfoxide). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 437–443     

Preparation of carboxyl‐end‐group polyacrylamide with low polydispersity by ATRP initiated with chloroacetic acid

Atom transfer radical polymerization (ATRP) of acrylamide was successfully carried out with chloroacetic acid as initiator and CuCl/N,N,N′,N′‐tetramethylethylenediamine (TMEDA) as catalyst either in water at 80 °C or in glycerol–water (1:1 v/v) medium at 130 °C. In both cases, carboxyl‐end‐group polyacrylamide was obtained with lower polydispersity ranging from 1.03 to 1.44 depending on the polymerization condition. Polymerization kinetics showed that the polymerizations proceeded with a living/controlled nature and accelerated at a higher temperature. The effect of pH in the reaction system on the polymerizations was further studied, revealing that chloroacetic acid not only served as a functional initiator for the ATRP of acrylamde but also provided the acidic polymerization condition, which effectively protected the ATRP of acrylamide from the unexpected complexation and cyclization side‐reactions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3956–3965, 2007     

One‐step synthesis of poly(N‐vinylpyrrolidone)‐b‐poly(l‐lactide) block copolymers using a dual initiator for RAFT polymerization and ROP

Amphiphilic, biocompatible poly(N‐vinylpyrrolidone)‐b‐poly(l ‐lactide) (PVP‐b‐PLLA) block polymers were synthesized at 60 °C using a hydroxyl‐functionalized N,N‐diphenyldithiocarbamate reversible addition–fragmentation chain transfer (RAFT) agent, 2‐hydroxyethyl 2‐(N,N‐diphenylcarbamothioylthio)propanoate (HDPCP), as a dual initiator for RAFT polymerization and ring‐opening polymerization (ROP) in a one‐step procedure. 4‐Dimethylamino pyridine was used as the ROP catalyst for l ‐lactide. The two polymerization reactions proceeded in a controlled manner, but their polymerization rates were affected by the other polymerization process. This one‐step procedure is believed to be the most convenient method for synthesizing PVP‐b‐PLLA block copolymers. HDPCP can also be used for the one‐step synthesis of poly(N‐vinylcarbazole)‐b‐PLLA block copolymers. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1607–1613     

Macromolecular brushes synthesized by “grafting from” approach based on “click chemistry” and RAFT polymerization

Well‐defined macromolecular brushes with poly(N‐isopropyl acrylamide) (PNIPAM) side chains on random copolymer backbones were synthesized by “grafting from” approach based on click chemistry and reversible addition‐fragmentation chain transfer (RAFT) polymerization. To prepare macromolecular brushes, two linear random copolymers of 2‐(trimethylsilyloxy)ethyl methacrylate (HEMA‐TMS) and methyl methacrylate (MMA) (poly(MMA‐co‐HEMA‐TMS)) were synthesized by atom transfer radical polymerization and were subsequently derivated to azide‐containing polymers. Novel alkyne‐terminated RAFT chain transfer agent (CTA) was grafted to polymer backbones by copper‐catalyzed 1,3‐dipolar cycloaddition (azide‐alkyne click chemistry), and macro‐RAFT CTAs were obtained. PNIPAM side chains were prepared by RAFT polymerization. The macromolecular brushes have well‐defined structures, controlled molecular weights, and molecular weight distributions (M_w/M_n ≦ 1.23). The RAFT polymerization of NIPAM exhibited pseudo‐first‐order kinetics and a linear molecular weight dependence on monomer conversion, and no detectable termination was observed in the polymerization. The macromolecular brushes can self‐assemble into micelles in aqueous solution. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 443–453, 2010     

Synthesis of 4μ‐PS2PEO2, 4μ‐PS2PCL2, 4μ‐PI2PEO2, and 4μ‐PI2PCL2 star‐shaped copolymers by the combination of glaser coupling with living anionic polymerization and ring‐opening polymerization

4μ‐A₂B₂ star‐shaped copolymers contained polystyrene (PS), poly(isoprene) (PI), poly(ethylene oxide) (PEO) or poly(ε‐caprolactone) (PCL) arms were synthesized by a combination of Glaser coupling with living anionic polymerization (LAP) and ring‐opening polymerization (ROP). Firstly, the functionalized PS or PI with an alkyne group and a protected hydroxyl group at the same end were synthesized by LAP and then modified by propargyl bromide. Subsequently, the macro‐initiator PS or PI with two active hydroxyl groups at the junction point were synthesized by Glaser coupling in the presence of pyridine/CuBr/N,N,N ′,N ″,N ″‐penta‐methyl diethylenetri‐amine (PMDETA) system and followed by hydrolysis of protected hydroxyl groups. Finally, the ROP of EO and ε‐CL monomers was carried out using diphenylmethyl potassium (DPMK) and tin(II)‐bis(2‐ethylhexanoate) (Sn(Oct)₂) as catalyst for target star‐shaped copolymers, respectively. These copolymers and their intermediates were well characterized by SEC, ¹H NMR, MALDI‐TOF mass spectra and FT‐IR in details. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Atypical transition temperature dependence of poly(N‐isopropylacrylamide) and poly(N‐isopropylacrylamide‐co‐acrylamide) nanocomposites on the content of exfoliated montmorillonites

Exfoliated montmorillonite (MMT)/poly(N‐isopropylacrylamide) (PNIPAAm) and MMT/poly(N‐isopropylacrylamide‐co‐acrylamide) [P(NIPAAm‐co‐AAm)] nanocomposites were fabricated by soap‐free emulsion polymerization. Interestingly, as the content of MMT was increased from 0 to 10 wt %, the glass transition temperature of MMT/PNIPAAm was decreased from 145 to 122 °C, whereas that of the MMT/P(NIPAAm‐co‐AAm) increased from 95 to 153 °C. Although the lower critical solution temperature (LCST) of 32 °C for the MMT/PNIPAAm nanocomposites in aqueous solutions was slightly increased with the content of MMT, that of the MMT/P(NIPAAm‐co‐AAm) was decreased from 70 to 65 °C. A mechanism that the hydrogen bonds between the amide groups of PNIPAAm were interfered by the exfoliated MMT nano‐platelets for the MMT/PNIPAAm nanocomposites and the preferred absorption of acrylamide units to the MMT nanoplatelets rather than N‐isopropylacrylamide in the MMT/P(NIPAAm‐co‐AAm) nanocomposites was suggested to interpret these unusual transition behavior. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 524–530, 2009     

Preparation and characterization of crosslinked poly(N,N‐diethylacrylamide‐co‐2‐hydroxyethyl methacrylate) resins and their application as support in solid‐phase peptide synthesis

Novel hydrophilic and thermosensitive poly(N,N‐diethylacrylamide‐co‐2‐hydroxyethyl methacrylate) resins were prepared by inverse suspension polymerization with N,N′‐methylenebis(acrylamide) as a crosslinker. The effects of chemical composition and degree of crosslinking on the polymerization were investigated. The polymer resins were characterized by elemental analysis, infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy. The thermosensitivity of the crosslinked resins was demonstrated by their lower critical swelling temperatures. The swelling and deswelling volume of the beads in water varied depending on the molar fraction of the N,N‐diethylacrylamide. These beads swelled extensively in a variety of common solvents. They had high loadings of functional hydroxyl groups and were used as supports in the solid‐phase synthesis of an oligopeptide. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1681–1690, 2003