Samarium enolate on crosslinked polystyrene beads. III. Anionic initiator for well‐defined synthesis of poly(hydroxyethyl methacrylate) on solid support

A solid‐supported samarium enolate successfully initiated the polymerization of 2‐(trimethylsilyloxy)ethyl methacrylate (TMS‐HEMA) through the living anionic process. In addition, the silyl group was readily removed by treatment of the beads with a weak acid to afford the corresponding well‐defined poly(methacrylate) having a hydroxyethyl group in the side chain (PHEMA). The hydroxyl group of the immobilized PHEMA on the beads was successfully acetylated to give poly(2‐acetoxyethyl methacrylate), which could be quantitatively isolated from the beads by trifluoroacetic acid treatment. Moreover, the hydroxyl group of the immobilized PHEMA could be utilized as an initiator for acid promoted ring opening polymerization of lactone to yield the corresponding graft copolymer. In this method, the residual and excess reagents could be removed by filtration, which demonstrated the applicability of the present technique to a novel method for construction of functional polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4417–4423, 2004     

Synthesis and characterization of well‐defined poly(2‐hydroxyethyl methacrylate‐co‐styrene)‐graft‐poly(ε‐caprolactone) by sequential controlled polymerization

A new graft copolymer, poly(2‐hydroxyethyl methacrylate‐co‐styrene) ‐graft‐poly(?‐caprolactone), was prepared by combination of reversible addition‐fragmentation chain transfer polymerization (RAFT) with coordination‐insertion ring‐opening polymerization (ROP). The copolymerization of styrene (St) and 2‐hydroxyethyl methacrylate (HEMA) was carried out at 60 °C in the presence of 2‐phenylprop‐2‐yl dithiobenzoate (PPDTB) using AIBN as initiator. The molecular weight of poly (2‐hydroxyethyl methacrylate‐co‐styrene) [poly(HEMA‐co‐St)] increased with the monomer conversion, and the molecular weight distribution was in the range of 1.09 ～ 1.39. The ring‐opening polymerization (ROP) of ?‐caprolactone was then initiated by the hydroxyl groups of the poly(HEMA‐co‐St) precursors in the presence of stannous octoate (Sn(Oct)₂). GPC and ¹H‐NMR data demonstrated the polymerization courses are under control, and nearly all hydroxyl groups took part in the initiation. The efficiency of grafting was very high. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5523–5529, 2004     

Synthesis of well‐defined amphiphilic graft copolymer bearing poly(2‐acryloyloxyethyl ferrocenecarboxylate) side chains via successive SET‐LRP and ATRP

A series of well‐defined ferrocene‐based amphiphilic graft copolymers, consisting of poly(N‐isopropylacrylamide)‐b‐poly(ethyl acrylate) (PNIPAM‐b‐PEA) backbone and poly(2‐acryloyloxyethyl ferrocenecarboxylate) (PAEFC) side chains, were synthesized by the combination of single‐electron‐transfer living radical polymerization (SET‐LRP) and atom transfer radical polymerization (ATRP). A new ferrocene‐based monomer, 2‐(acryloyloxy)ethyl ferrocenecarboxylate (AEFC), was prepared first and it can be polymerized via ATRP in a controlled way using methyl 2‐bromopropionate as initiator and CuBr/PMDETA as catalytic system in DMF at 40 °C. PNIPAM‐b‐PEA backbone was synthesized by sequential SET‐LRP of NIPAM and HEA at 25 °C using CuCl/Me₆TREN as catalytic system followed by the transformation into the macroinitiator by treating the pendant hydroxyls with α‐bromoisobutyryl bromide. The targeted well‐defined graft copolymers with narrow molecular weight distributions (M_w/M_n < 1.20) were synthesized via ATRP of AEFC initiated by the macroinitiator. The electro‐chemical behaviors of PAEFC homopolymer and PNIPAM‐b‐(PEA‐g‐PAEFC) graft copolymer were studied by cyclic voltammetry. Micellar properties of PNIPAM‐b‐(PEA‐g‐PAEFC) were investigated by transmission electron microscopy and dynamic light scattering. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4346–4357, 2009     

Synthesis of well‐defined AB20‐type star polymers with cyclodextrin‐core by combination of NMP and ATRP

The synthesis of an AB₂₀‐type heteroarm star polymer consisting of a polystyrene arm and 20‐arms of poly(methyl methacrylate) or poly(tert‐butyl acrylate) was carried out using the combination of nitroxide‐mediated polymerization (NMP) and atom transfer radical polymerization (ATRP). The NMP of styrene was carried out using mono‐6‐[4‐(1′‐(2″,2″,6″,6″‐tetramethyl‐1″‐piperidinyloxy)‐ethyl)benzamido]‐β‐cyclodextrin peracetate ( 1 ) to afford end‐functionalized polystyrene with an acetylated β‐cyclodextrin (β‐CyD) unit (prepolymer 2 ) with a number‐average molecular weight (M_n) of 11700 and a polydispersity (M_w/M_n) of 1.17. After deacetylation of prepolymer 2 , the resulting polymer was reacted with 2‐bromoisobutyric anhydride to give end‐functionalized polystyrene with 20(2‐bromoisobutyrol)s β‐CyD, macroinitiator 4 . The copper (I)‐mediated ATRP of methyl methacrylate (MMA) and tert‐butyl acrylate (tBA) was carried out using macroinitiator 4 . The resulting polymers were isolated by SEC fractionation to produce AB₂₀‐type star polymers with a β‐CyD‐core, 5 . The well‐defined structure of 5 with weight‐average molecular weight (M_w)s of 13,500–65,300 and M_w/M_n's of 1.26–1.28 was demonstrated by SEC and light scattering measurements. The arm polymers were separated from 5 by destruction with 28 wt % sodium methoxide in order to analyze the details of their characteristic structure. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4271–4279, 2005     

RAFT‐mediated synthesis and temperature‐induced responsive properties of poly(2‐(2‐methoxyethoxy)ethyl methacrylate) brushes

Well‐defined, high‐density poly(2‐(2‐methoxyethoxy)ethyl methacrylate) [poly(MEO₂MA)] brushes were fabricated through a reliable strategy by the combination of self‐assembly of a monolayer of 3‐aminopropyltrimethoxy silane on silicon surface to immobilize 4‐cyano‐4‐(dodecylsulfanylthiocarbonyl)sulfanyl pentanoic acid chain transfer agent and reversible addition‐fragmentation chain transfer‐mediated polymerization of MEO₂MA. The whole fabrication process of the poly(MEO₂MA) brushes was followed by water contact angle, grazing angle‐Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and atomic force microscopy. Characterization of the poly(MEO₂MA) brushes, such as molecular weight and thickness determination, were measured by gel permeation chromatography and ellipsometry, and the grafting density was estimated. The temperature‐responsive property of the poly(MEO₂MA) brushes was further investigated and the result verified the brush‐to‐mushroom phase transition of the poly(MEO₂MA) chains from low to high temperature. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis of poly(p‐phenylene)‐poly(4‐diphenylaminostyrene) bipolar block copolymers with a well‐controlled and defined polymer chain structure

A poly(p‐phenylene) (PPP)‐poly(4‐diphenylaminostyrene) (PDAS) bipolar block copolymer was synthesized for the first time. A prerequisite prepolymer, poly(1,3‐cyclohexadiene) (PCHD)‐PDAS binary block copolymer, in which the PCHD block consisted solely of 1,4‐cyclohexadiene (1,4‐CHD) units, was synthesized by living anionic block copolymerization of 1,3‐cyclohexadiene and 4‐diphenylaminostyrene. To obtain the PPP‐PDAS bipolar block copolymer, the dehydrogenation of this prepolymer with quinones was examined, and tetrachloro‐1,2‐(o)‐benzoquinone was found to be an appropriate dehydrogenation reagent. This dehydrogenation reaction was remarkably accelerated by ultrasonic irradiation, effectively yielding the target PPP‐PDAS bipolar block copolymer. The hole and electron drift mobilities for PPP‐PDAS bipolar block copolymer were both on the order of 10^?3 to 10^?4 cm²/V·s, with a negative slope when plotted against the square root of the applied field. Therefore, this bipolar block copolymer was found to act as a bipolar semi‐conducting copolymer. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Atom transfer radical polymerization of methyl methacrylate by copper(I)‐pyridine‐2‐carboximidate catalysts

Pyridine‐2‐carboximidates [methyl ( 1a ), ethyl ( 1b ), isopropyl ( 1c ), cyclopentyl ( 1d ), cyclohexyl ( 1e ), n‐octyl ( 1f ), and benzyl ( 1g )] were prepared from the reaction of 2‐cyanopyridine with the corresponding alcohols. Cyclopentyl‐substituted 1d was found to be a highly effective ligand for copper‐catalyzed atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA). For example, the observed rate constant for a CuBr/ 1d catalytic system was found to be nearly twice as high as the cyclohexyl‐substituted CuBr/ 1e catalytic system [k_obs = (1.19 vs 0.56) × 10^?4 s^?1). The effects of the solvents, temperature, catalyst/initiator, and solvent/monomer ratio on the ATRP of MMA were studied systematically for the CuBr/ 1d catalytic system. The optimum condition for the ATRP of MMA was found to be a 1:2:1:400 [CuBr]_o/[ 1d ]_o/[ethyl 2‐bromoisobutyrate]_o/[MMA]_o ratio at 60 °C in veratrole solution, which yielded well‐defined poly(MMA) with a narrow molecular weight distribution of 1.14. The catalytically active copper complex 2d was isolated from the reaction of CuBr with 1d . Narrow molecular weight distributions as low as 1.06 were achieved for the CuBr/ 1d catalytic system by employing 10% of the deactivator CuBr₂. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2747–2755, 2004     

Synthesis of well‐defined photoresist materials by SET‐LRP

Single electron transfer‐living radical polymerization (SET‐LRP) provides an excellent tool for the straightforward synthesis of well‐defined macromolecules. Heterogeneous Cu(0)‐ catalysis is employed to synthesize a novel photoresist material with high control over the molecular architecture. Poly(γ‐butyrolactone methacrylate)‐co‐(methyladamantly methacrylate) was synthesized. Kinetic experiments were conducted demonstrating that both monomers, γ‐butyrolactone methacrylate (GBLMA) and methyl adamantly methacrylate (MAMA), are successfully homopolymerized. In both cases polymerization kinetic is of first order and the molecular weights increase linearly with conversion. The choice of a proper solvent was decisive for the SET‐LRP process and organic solvent mixtures were found to be most suitable. Also, the kinetic of the copolymerization of GBLMA and MAMA was investigated. Following first order kinetics in overall monomer consumption and exhibiting a linear relationship between molecular weights and conversion a “living” process was established. This allowed for the straightforward synthesis of well‐defined photoresist polymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2251–2255, 2010     

Synthesis of well‐defined multigraft copolymers by a two‐step living radical polymerization with nitroxyl‐functionalized poly(methyl methacrylate)

Novel multigraft copolymers of poly(methyl methacrylate‐graft‐polystyrene) (PMMA‐g‐PS) in which the number of graft PS side chains was varied were prepared by a subsequent two‐step living radical copolymerization approach. A polymerizable 4‐vinylbezenyl 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO) monomer (STEMPO), which functioned as both a monomer and a radical trapper, was placed in a low‐temperature atom transfer radical polymerization (60°C) process of methyl methacrylate with ethyl 2‐bromopronionate (EPNBr) as an initiator to gain ethyl pronionate‐capped prepolymers with TEMPO moieties, PMMA‐STEMPOs. The number of TEMPO moieties grafted on the PMMA backbone could be designed by varying STEMPO/EPNBr, for example, the ratios of 1/2, 2/3, or 3/4 gained one, two, or three graft TEMPO moieties, respectively. The resulting prepolymers either as a macromolecular initiator or a trapper copolymerized with styrene in the control of stable free‐radical polymerization at an elevated temperature (120 °C), producing the corresponding multigraft copolymers, PMMA‐g‐PSs. The nitroxyl‐functionalized PMMA prepolymers produced a relatively high initiation efficiency (>0.8) as a result of the stereohindrance and slow diffusion of TEMPO moieties connected on the long PMMA backbone. The polymerization kinetics in two processes showed a living radical polymerization characteristic. The molecular structures of these prepolymers and graft copolymers were well characterized by combining Fourier transform infrared spectroscopy, gel permeation chromatography, chemical element analysis, and ¹H NMR. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1876–1884, 2002     

Synthesis of well‐defined cyclodextrin‐core star polymers

The synthesis of 21‐arm methyl methacrylate (MMA) and styrene star polymers is reported. The copper (I)‐mediated living radical polymerization of MMA was carried out with a cyclodextrin‐core‐based initiator with 21 independent discrete initiation sites: heptakis[2,3,6‐tri‐O‐(2‐bromo‐2‐methylpropionyl]‐β‐cyclodextrin. Living polymerization occurred, providing well‐defined 21‐arm star polymers with predicted molecular weights calculated from the initiator concentration and the consumed monomer as well as low polydispersities [e.g., poly(methyl methacrylate) (PMMA), number‐average molecular weight (M_n) = 55,700, polydispersity index (PDI) = 1.07; M_n = 118,000, PDI = 1.06; polystyrene, M_n = 37,100, PDI = 1.15]. Functional methacrylate monomers containing poly(ethylene glycol), a glucose residue, and a tert‐amine group in the side chain were also polymerized in a similar fashion, leading to hydrophilic star polymers, again with good control over the molecular weight and polydispersity (M_n = 15,000, PDI = 1.03; M_n = 36,500, PDI = 1.14; and M_n = 139,000, PDI = 1.09, respectively). When styrene was used as the monomer, it was difficult to obtain well‐defined polystyrene stars at high molecular weights. This was due to the increased occurrence of side reactions such as star–star coupling and thermal (spontaneous) polymerization; however, low‐polydispersity polymers were achieved at relatively low conversions. Furthermore, a star block copolymer consisting of PMMA and poly(butyl methacrylate) was successfully synthesized with a star PMMA as a macroinitiator (M_n = 104,000, PDI = 1.05). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2206–2214, 2001     

Synthesis of well‐defined syndiotactic poly(methyl methacrylate) with low‐temperature atom transfer radical polymerization in fluoroalcohol

The copper‐mediated atom transfer radical polymerization of methyl methacrylate (MMA) in 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) was studied to simultaneously control the molecular weight and tacticity. The polymerization using tris[2‐(dimethylamino)ethyl]amine (Me₆TREN) as a ligand was performed even at ?78°C with a number‐average molecular weight (M_n) of 13,400 and a polydispersity (weight‐average molecular weight/number‐average molecular weight) of 1.31, although the measured M_n's were much higher than the theoretical ones. The addition of copper(II) bromide (CuBr₂) apparently affected the early stage of the polymerization; that is, the polymerization could proceed in a controlled manner under the condition of [MMA]₀/[methyl α‐bromoisobutyrate]₀/[CuBr]₀/[CuBr₂]₀/[Me₆TREN]₀ = 200/1/1/0.2/1.2 at ?20°C with an MMA/HFIP ratio of 1/4 (v/v). For the field desorption mass spectrum of Cu^IBr/Me₆TREN in HFIP, there were [Cu(Me₆TREN)Br]⁺ and [Cu(Me₆TREN)OCH(CF₃)₂]⁺, indicating that HFIP should coordinate to the Cu^I/Me₆TREN complex. The syndiotacticity of the obtained poly(methyl methacrylate)s increased with the decreasing polymerization temperature; the racemo content was 84% for ?78°C, 77% for ?30°C, 75% for ?20°C, and 63% for 30°C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1436–1446, 2006     

Synthesis of well‐defined,soluble poly(3‐alkyl‐4‐benzamide) by chain‐growth condensation polymerization

Well‐defined poly(3‐alkyl‐4‐benzamide) was synthesized by means of chain‐growth condensation polymerization of phenyl 3‐octyl‐4‐(4‐octyloxybenzyl(OOB)amino)benzoate ( 1c ) from initiator 2 , followed by removal of the OOB groups on amide nitrogen of poly 1c . Polymerization of 1c with phenyl 4‐(trifluoromethyl)benzoate ( 2b ) in the presence of 1,1,1,3,3,3‐hexamethyldisilazide (LiHMDS) and LiCl in THF at ?10 °C gave poly 1c with a narrow molecular weight distribution (M_w/M_n ≤ 1.08) and a well‐defined molecular weight (M_n = 4480–12,700) determined by the feed ratio of monomer to initiator (from 10 to 30). The OOB groups of poly 1c were removed with H₂SO₄ to give the corresponding N‐unsubstituted poly(p‐benzamide) (poly 1c′ ) with low polydispersity. The solublity of poly 1c′ in polar organic solvents was dramatically higher than that of poly(p‐benzamide), demonstrating that introduction of an alkyl group on the aromatic ring is very effective for improving the solubility of poly(p‐benzamide). © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 360–365     

Syntheses and micellar properties of well‐defined amphiphilic AB2 and A2B Y‐shaped miktoarm star copolymers of ε‐caprolactone and 2‐(dimethylamino)ethyl methacrylate

Well‐defined amphiphilic PCL‐b‐(PDMA)₂ and (PCL)₂‐b‐PDMA Y‐shaped miktoarm star copolymers and PCL‐b‐PDMA linear diblock copolymer were synthesized via a combination of ring‐opening polymerization (ROP) and atom transfer radical polymerization (ATRP), where PCL is poly (ε‐caprolactone) and PDMA is poly(2‐(dimethylamino)ethyl methacrylate). All of these three types of copolymers have comparable PCL contents and overall molecular weights. The PCL block is hydrophobic while the PDMA block is hydrophilic, and they behave like polymeric surfactants and self‐assemble into PCL‐core micelles in aqueous media. The chain architectural effects on the micellization properties, including the aggregation number, size, polydispersity, and micelle densities of (PCL₂₉)₂‐b‐PDMA₄₅, PCL₆₁‐b‐(PDMA₂₄)₂, and PCL₅₆‐b‐PDMA₄₉ in dilute aqueous solution, were then explored by dynamic and static laser light scattering (LLS). The intensity–average hydrodynamic radius, 〈R_h〉, the aggregation number per micelle, N_agg, and the core radius, R_core, of the PCL‐core micelles all increased in the order PCL₆₁‐b‐(PDMA₂₄)₂ < (PCL₂₉)₂‐b‐PDMA₄₅ < PCL₅₆‐b‐PDMA₄₉. The surface area occupied per soluble PDMA block at the core/corona interface increased in the order PCL₆₁‐b‐(PDMA₂₄)₂ < PCL₅₆‐b‐PDMA₄₉ < (PCL₂₉)₂‐b‐PDMA₄₅. PCL₆₁‐b‐(PDMA₂₄)₂ micelles had the largest overall micelle density, possibly because of that the presence of two soluble PDMA arms at the junction point favors the bending of the core–corona interface and thus the formation of densely‐packed core‐shell nanostructures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1446–1462, 2007     

Poly(methyl methacrylate‐co‐pentaerythritol tetraacrylate‐co‐butyl methacrylate)‐g‐polystyrene: Synthesis and high oil‐absorption property

Well‐defined high oil‐absorption resin was successfully prepared via living radical polymerization on surface of polystyrene resin‐supported N‐chlorosulfonamide group utilizing methyl methacrylate and butyl methacrylate as monomers, ferric trichloride/iminodiacetic acid (FeCl₃/IDA) as catalyst system, pentaerythritol tetraacrylate as crosslinker, and L ‐ascorbic acid as reducing agent. The polymerization proceeded in a “living” polymerization manner as indicated by linearity kinetic plot of the polymerization. Effects of crosslinker, catalyst, macroinitiator, reducing agent on polymerization and absorption property were discussed in detail. The chemical structure of sorbent was determined by FTIR spectrometry. The oil‐absorption resin shows a toluene absorption capacity of 21 g g^?1. The adsorption of oil behaves as pseudo‐first‐order kinetic model rather than pseudo‐second‐order kinetic model. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis of poly(2‐hydroxyethyl methacrylate) in protic media through atom transfer radical polymerization using activators generated by electron transfer

Atom transfer radical polymerization (ATRP) using activators generated by electron transfer (AGET) was investigated for the controlled polymerization of 2‐hydroxyethyl methacrylate (HEMA) in a protic solvent, a 3/2 (v/v) mixture of methyl ethyl ketone and methanol. The AGET process enabled ATRP to be started with an air‐stable Cu(II) complex that was reduced in situ by tin(II) 2‐ethylhexanoate. The reaction temperature, Cu catalysts with different ligands, and variation of the initial concentration ratio of HEMA to the initiator were examined for the synthesis of well‐controlled poly(2‐hydroxyethyl methacrylate) and a poly(methyl methacrylate)‐b‐poly(2‐hydroxyethyl methacrylate) block copolymer. The level of control in AGET ATRP was similar to that in normal ATRP in protic solvents, and this resulted in a linear increase in the molecular weight with the conversion and a narrow molecular weight distribution (weight‐average molecular weight/number‐average molecular weight < 1.3). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3787–3796, 2006     

β‐Hydrogen transfer from poly(methyl methacrylate) propagating radicals to the nitroxide SG1: Analysis of the chain‐end and determination of the rate constant

Methyl methacrylate (MMA) was polymerized in bulk at 70 °C in the presence of an alkoxyamine initiator with low dissociation temperature (the so‐called BlocBuilder?) and increasing amounts of free N‐tert‐butyl‐N‐(1‐diethylphosphono‐2,2‐dimethylpropyl) nitroxide (SG1). Low final monomer conversions were reached, indicating a loss in radical activity due to side reactions such as irreversible homoterminations between the propagating radicals and β‐hydrogen transfer (also called disproportionation) from a propagating radical to a free‐SG1 nitroxide. Proton NMR and MALDI‐TOF mass spectrometry were used to analyze the polymer chain‐ends and to clearly identify the main mechanism of irreversible termination. In particular, it was shown that all polymer chains were terminated by an alkene function in the presence of a large excess of free SG1, meaning that β‐hydrogen transfer from PMMA propagating radicals to the nitroxide SG1 was the major chain‐stopping event. On the other hand, for a low excess of free SG1, the two termination modes coexisted. Kinetic modeling was then performed using the PREDICI software, and the rate constant of β‐hydrogen transfer, k_βHtr, was estimated to be 1.69 × 10³ L mol^?1 s^?1 at 70 °C. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6333–6345, 2008     

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     

Gel formation in atom transfer radical polymerization of 2‐(N,N‐dimethylamino)ethyl methacrylate and ethylene glycol dimethacrylate

Copolymers of 2‐(N,N‐dimethylamino)ethyl methacrylate (DMAEMA) and ethylene glycol dimethacrylate (EGDMA) were synthesized via atom transfer radical polymerization using ethyl 2‐bromoisobutyrate as the initiator, Cu(I)Br as the catalyst, and 1,1,4,7,10,10‐hexamethyltriethylene tetramine as the ligand. At low crosslinker levels, the polymerizations followed the first‐order kinetics. However, when the crosslinker level was above 10 mol %, the ln([M]₀/[M]) versus time curves showed deceleration at medium conversions because of the higher reactivity of EGDMA than that of DMAEMA. An acceleration at high conversions was also observed and probably caused by the diffusion limitations of catalyst/ligand complex in the polymer network. The hydrogels were characterized by swelling experiments, and the sol polymers were characterized by the size exclusion chromatographic technique to determine the number‐average molecular weight and polydispersity. The gel data were analyzed and, via a comparison to Flory's gelation theory, found to be more homogeneous than similar hydrogels prepared by conventional free‐radical polymerization methods. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3780–3788, 2001     

Synthesis of fluorescent,dansyl end‐functionalized PMMA and poly(methyl methacrylate‐b‐phenanthren‐1‐yl‐methacrylate) diblock copolymers,at ambient temperature

The polymerization of MMA, at ambient temperature, mediated by dansyl chloride is investigated using controlled radical polymerization methods. The solution ATRP results in reasonably controlled polymerization with PDI < 1.3. The SET‐LRP polymerization is less controlled while SET‐RAFT polymerization is controlled producing poly(methyl methacrylate) (PMMA) with the PDI < 1.3. In all the cases, the polymerization rate followed first order kinetics with respect to monomer conversion and the molecular weight of the polymer increased linearly with conversion. The R group in the CTAs do not appear to play a key role in controlling the propagation rate. SET‐RAFT method appears to be a simpler tool to produce methacrylate polymers, under ambient conditions, in comparison with ATRP and SET‐LRP. Fluorescent diblock copolymers, P(MMA‐b‐PhMA), were synthesized. These were highly fluorescent with two distinguishable emission signatures from the dansyl group and the phenanthren‐1‐yl methacrylate block. The fluorescence emission spectra reveal interesting features such as large red shift when compared to the small molecule. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and characterization of amphiphilic copolymer of linear poly(ethylene oxide) linked with [poly(styrene‐co‐2‐hydroxyethyl methacrylate)‐graft‐poly(ε‐caprolactone)] using sequential controlled polymerization

A well‐defined amphiphilic copolymer of ‐poly(ethylene oxide) (PEO) linked with comb‐shaped [poly(styrene‐co‐2‐hydeoxyethyl methacrylate)‐graft‐poly(ε‐caprolactone)] (PEO‐b‐P(St‐co‐HEMA)‐g‐PCL) was successfully synthesized by combination of reversible addition‐fragmentation chain transfer polymerization (RAFT) with ring‐opening anionic polymerization and coordination–insertion ring‐opening polymerization (ROP). The α‐methoxy poly(ethylene oxide) (mPEO) with ω,3‐benzylsulfanylthiocarbonylsufanylpropionic acid (BSPA) end group (mPEO‐BSPA) was prepared by the reaction of mPEO with 3‐benzylsulfanylthiocarbonylsufanyl propionic acid chloride (BSPAC), and the reaction efficiency was close to 100%; then the mPEO‐BSPA was used as a macro‐RAFT agent for the copolymerization of styrene (St) and 2‐hydroxyethyl methacrylate (HEMA) using 2,2‐azobisisobutyronitrile as initiator. The molecular weight of copolymer PEO‐b‐P(St‐co‐HEMA) increased with the monomer conversion, but the molecular weight distribution was a little wide. The influence of molecular weight of macro‐RAFT agent on the polymerization procedure was discussed. The ROP of ε‐caprolactone was then completed by initiation of hydroxyl groups of the PEO‐b‐P(St‐co‐HEMA) precursors in the presence of stannous octoate (Sn(Oct)₂). Thus, the amphiphilic copolymer of linear PEO linked with comb‐like P(St‐co‐HEMA)‐g‐PCL was obtained. The final and intermediate products were characterized in detail by NMR, GPC, and UV. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 467–476, 2006