Efficient synthesis of monodisperse,highly crosslinked,and “living” functional polymer microspheres by the ambient temperature iniferter‐induced “living” radical precipitation polymerization

The facile and efficient one‐pot synthesis of monodisperse, highly crosslinked, and “living” functional copolymer microspheres by the ambient temperature iniferter‐induced “living” radical precipitation polymerization (ILRPP) is described for the first time. The simple introduction of iniferter‐induced “living” radical polymerization (ILRP) mechanism into precipitation polymerization system, together with the use of ethanol solvent, allows the direct generation of such uniform functional copolymer microspheres. The polymerization parameters (including monomer loading, iniferter concentration, molar ratio of crosslinker to monovinyl comonomer, and polymerization time and scale) showed much influence on the morphologies of the resulting copolymer microspheres, thus permitting the convenient tailoring of the particle sizes by easily tuning the reaction conditions. In particular, monodisperse poly(4‐vinylpyridine‐co‐ethylene glycol dimethacrylate) microspheres were prepared by the ambient temperature ILRPP even at a high monomer loading of 18 vol %. The general applicability of the ambient temperature ILRPP was confirmed by the preparation of uniform copolymer microspheres with incorporated glycidyl methacrylate. Moreover, the “livingness” of the resulting polymer microspheres was verified by their direct grafting of hydrophilic polymer brushes via surface‐initiated ILRP. Furthermore, a “grafting from” particle growth mechanism was proposed for ILRPP, which is considerably different from the “grafting to” particle growth mechanism in the traditional precipitation polymerization. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Surface‐initiated atom transfer radical polymerization grafting of poly(2,2,2‐trifluoroethyl methacrylate) from flat silicon wafer surfaces

Poly(2,2,2‐trifluoroethyl methacrylate) (PTFEMA), a partially fluorinated polymer, was directly grafted from silicon wafer surfaces by a surface‐initiated atom‐transfer radical polymerization (ATRP). The polymer layer thickness increased linearly with monomer conversion and molecular weight of free polymers in solution. The thickness was mainly determined by the experimental conditions such as activator/deactivator ratio, monomer/catalyst ratio, and monomer concentration. PTFEMA layers of more than 100‐nm thick were obtained. The grafted PTFEMA chains were “living” and allowed the extension of a second block of PMMA. X‐ray photoelectron spectroscopy study showed that the chemical compositions at the surfaces agreed well with their theoretical values. A novel surface‐attachable difunctional initiator was also synthesized and applied to the grafting of PTFEMA. The grafting density was doubled using this difunctional initiator, from 0.48 to 0.86 chains/nm². © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1252–1262, 2006     

Regenerable‐Catalyst‐Aided,Opened to Air and Sunlight‐Driven “CuAAC&ATRP” Concurrent Reaction for Sequence‐Controlled Copolymer

An ideal stimuli‐responsive controlled/living radical polymerization should have the ability to manipulate the reaction through spatiotemporal “on/off” controls, achieving the polymerization under fully open conditions and allowing for precise control over macromolecular architecture with defined molecular weights and monomer sequence. In this contribution, the photo (sunlight)‐induced electron transfer atom transfer radical‐polymerization (PET‐ATRP) can be realized to be reversibly activated and deactivated under fully open conditions utilizing one‐component copper(II) thioxanthone carboxylate as multifunctional photocatalyst and oxygen scavenger. The polymerization behaviors are investigated, presenting controlled features with first‐order kinetics and linear relationships between molecular weights and monomer conversions. More importantly, “CuAAC&ATRP” concurrent reaction combining PET‐ATRP, photodriven deoxygenation, and photoactivated CuAAC click reaction is successfully employed to synthesize the sequence‐defined multiblock functional copolymers, in which the iterative monomer additions can be easily manipulated under fully open conditions.     

Controlled grafting from poly(vinylidene fluoride) films by surface‐initiated reversible addition–fragmentation chain transfer polymerization

A reversible addition–fragmentation chain transfer (RAFT) polymerization technique was applied to graft polymerize brushes of poly(methyl methacrylate) (PMMA) and poly(poly(ethylene glycol) monomethacrylate) (PPEGMA) from poly(vinylidene fluoride) (PVDF) surfaces. PVDF surfaces were exposed to aqueous LiOH, followed by successive reductions with NaBH₄ and DIBAL‐H to obtain hydroxyl functionality. Azo‐functionalities, as surface initiators for grafting, were immobilized on the PVDF surfaces by esterification of 4,4′‐azobis(4‐cyanopentanoic acid) and the surface hydroxyl groups. The chemical composition and surface topography of the graft‐functionalized PVDF surfaces were characterized by X‐ray photoelectron spectroscopy, attenuated total reflectance‐FTIR spectroscopy, and atomic force microscopy. Kinetics studies revealed a linear increase in the graft concentration of PMMA and PPEGMA with the reaction time, indicating that the chain growth from the surface was consistent with a “controlled” or “living” process. The living chain ends were used as the macroinitiator for the synthesis of diblock copolymer brushes. Water contact angles on PVDF films were reduced by surface grafting of PEGMA and MMA. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3071–3082, 2006     

Syntheses and characterization of block copolymers of poly(aliphatic ester) with clickable polyphosphoester

We report a series of biocompatible and biodegradable block copolymers of poly(ε‐caprolactone) with “clickable” polyphosphoester (PPE). The block copolymers are synthesized through controlled ring‐opening polymerization of five‐membered cyclic phosphoester monomer, propargyl ethylene phosphate (PAEP), initiated with poly(ε‐caprolactone) macroinitiator. The polymerization followed first‐order kinetics with living polymerization characteristics, thus the molecular weight and composition of copolymers are tunable by adjusting the feed ratio of PAEP monomer to macroinitiator. Azide‐functionalized poly(ethylene glycol) has been grafted to the copolymer to demonstrate the reactive feasibility by Cu(I)‐catalyzed “click” chemistry of azides and alkynes, generating “brush‐coil” polymers. The mild conditions associated with the click reaction are shown to be compatible with poly(ε‐caprolactone) and PPE backbones, rendering the click reaction a generally useful method for grafting numerous types of functionality onto the block copolymers. The block copolymers also show good biocompatibility to cells, suggesting their suitability for a range of biomaterial applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and characterization of star graft copolymers with asymmetric mixed “V‐shaped” side chains via “click” chemistry on a hyperbranched polyglycerol core

The star graft copolymers composed of hyperbranched polyglycerol (HPG) as core and well defined asymmetric mixed “V‐shaped” identical polystyrene (PS) and poly(tert‐butyl acrylate) as side chains were synthesized via the “click” chemistry. The V‐shaped side chain bearing a “clickable” alkyne group at the conjunction point of two blocks was first prepared through the combination of anionic polymerization of styrene (St) and atom transfer radical polymerization of tert‐butyl acrylate (tBA) monomer, and then “click” chemistry was conducted between the alkyne groups on the side chains and azide groups on HPG core. The obtained star graft copolymers and intermediates were characterized by gel permeation chromatography (GPC), GPC equipped with a multiangle laser‐light scattering detector (GPC‐MALLS), nuclear magnetic resonance spectroscopy and fourier transform infrared. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1308–1316, 2009     

Combining renewable gum rosin and lignin: Towards hydrophobic polymer composites by controlled polymerization

Rosin polymer–grafted lignin composites were prepared via “grafting from” atom transfer radical polymerization (ATRP) with the aid of 2‐bromoisobutyryl ester‐modified lignin as macroinitiators. Three different monomers derived from dehydroabietic acid (DA) were used for execution of grafting from ATRP, while DA was separately attached onto lignin by a simple esterification reaction. Kinetic studies indicated controlled and “living” characteristics of all monomer polymerizations. Thermal studies indicated that rosin polymer–grafted lignin composites exhibited glass transition temperatures in a broad temperature range from ～20 to 100°C. The grafting of both DA and rosin polymers significantly enhanced hydrophobicity of lignin. Static contact angle measurement of water droplets showed ～90° for all these rosin modified lignin composites. X‐ray photoelectron spectroscopy demonstrated that the surface of rosin–lignin composites was dominated with chemical compositions originating from the hydrocarbon rich rosin moiety. The impartation of hydrophobicity of rosin into lignin provided excellent water resistance of this class of renewable polymers, as all rosin‐modified lignin composites showed water uptake below 1.0 wt %. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

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     

Atom transfer radical polymerization of n‐butyl acrylate from silica nanoparticles

This article reports the synthesis of atom transfer radical polymerization (ATRP) of active initiators from well‐defined silica nanoparticles and the use of these ATRP initiators in the grafting of poly(n‐butyl acrylate) from the silica particle surface. ATRP does not require difficult synthetic conditions, and the process can be carried out in standard solvents in which the nanoparticles are suspended. This “grafting from” method ensures the covalent binding of all polymer chains to the nanoparticles because polymerization is initiated from moieties previously bound to the surface. Model reactions were first carried out to account for possible polymerization in diluted conditions as it was required to ensure the suspension stability. The use of n‐butyl acrylate as the monomer permits one to obtain nanocomposites with a hard core and a soft shell where film formation is facilitated. Characterization of the polymer‐grafted silica was done from NMR and Fourier transform infrared spectroscopies, dynamic light scattering, and DSC. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4294–4301, 2001     

Hydrobromination of residual vinyl groups on divinylbenzene polymer particles followed by atom transfer radical surface graft polymerization

Rigid and monodisperse spherical polymer particles with 2.36 ± 0.18 μm diameter containing residual surface vinyl groups were prepared by photoinitiated precipitation polymerization of divinylbenzene. Anti‐Markovnikov addition of HBr to the surface vinyl groups yielded a 2‐bromoethyl functionality that was used as macroinitiator for atom transfer radical polymerization (ATRP), providing the possibility for further functionalization by controlled “grafting from” processes. This was demonstrated by grafting of glycidyl methacrylate brushes from the particle surface, using an ATRP system based on CuBr and pentamethyl diethylenetriamine. Existence of a methacrylic overlayer was verified by FTIR and XPS measurements, and the grafted particles were easily dispersed in water, confirming conversion of the particle surface from hydrophobic to hydrophilic. Hydrobromination of residual vinyl groups yields a macroinitiator that can be used for grafting of glycidyl methacrylate by ATRP. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1259–1265, 2009     

Degradable star polymers with high “click” functionality

Degradable polyester‐based star polymers with a high level of functionality in the arms were synthesized via the “arms first” approach using an acetylene‐functional block copolymer macroinitiator. This was achieved by using 2‐hydroxyethyl 2′‐methyl‐2′‐bromopropionate to initiate the ring‐opening polymerization (ROP) of caprolactone monomer followed by an atom transfer radical polymerization (ATRP) of a protected acetylene monomer, (trimethylsilyl)propargyl methacrylate. The hydroxyl end‐group of the resulting block copolymer macroinitiator was subsequently crosslinked under ROP conditions using a bislactone monomer, 4,4′‐bioxepanyl‐7,7′‐dione, to generate a degradable core crosslinked star (CCS) polymer with protected acetylene groups in the corona. The trimethylsilyl‐protecting groups were removed to generate a CCS polymer with an average of 1850 pendent acetylene groups located in the outer block segment of the arms. The increased functionality of this CCS polymer was demonstrated by attaching azide‐functionalized linear polystyrene via a copper (I)‐catalyzed cycloaddition reaction between the azide and acetylene groups. This resulted in a CCS polymer with “brush‐like” arm structures, the grafted segment of which could be liberated via hydrolysis of the polyester star structure to generate molecular brushes. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1485–1498, 2009     

Grafting of polymers onto and/or from silica surface during the polymerization of vinyl monomers in the presence of γ‐ray‐irradiated silica

The effects of radicals on silica surface, which were formed by γ‐ray irradiation, on the polymerization of vinyl monomers were investigated. It was found that the polymerization of styrene was remarkably retarded in the presence of γ‐ray‐irradiated silica above 60 °C, at which thermal polymerization of styrene is readily initiated. During the polymerization, a part of polystyrene formed was grafted onto the silica surface but percentage of grafting was very small. On the other hand, no retardation of the polymerization of styrene was observed in the presence of γ‐ray‐irradiated silica below 50 °C; the polymerization tends to accelerate and polystyrene was grafted onto the silica surface. Poly(vinyl acetate) and poly(methyl methacrylate) (MMA) were also grafted onto the surface during the polymerization in the presence of γ‐ray‐irradiated silica. The grafting of polymers onto the silica surface was confirmed by thermal decomposition GC‐MS. It was considered that at lower temperature, the grafting based on the propagation of polystyrene from surface radical (“grafting from” mechanism) preferentially proceeded. On the contrary, at higher temperature, the coupling reaction of propagating polymer radicals with surface radicals (“grafting onto” mechanism) proceeded to give relatively higher molecular weight polymer‐grafted silica. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2972–2979, 2006     

Synthesis of random polyampholyte brushes by atom transfer radical polymerization

We report the synthesis of random polyampholyte brushes containing 2‐(dimethylamino)ethyl methacrylate (DMAEMA) and methacrylic acid (MAA). The preparation of polyampholyte brushes is performed by the “grafting from” strategy using surface‐initiated atom transfer radical polymerization (ATRP). The first step consists in the formation of the self‐assembled monolayer of the ATRP initiator. Secondly, the chains are grown from the surface by controlled/“living” radical polymerization. The random copolymer brushes and the corresponding homopolymers brushes containing 2‐(dimethylamino)ethyl methacrylate and tert‐butyl methacrylate (^tBuMA) are prepared. The last step is the deprotection of the ^tBuMA form to the MAA segment by in situ hydrolysis reaction. The annealed DMAEMA group can also be converted to the quenched form by in situ quaternization reaction. This results in the formation of “annealed” and “semiannealed” polyampholyte brushes. The “annealed” polyampholyte corresponds to the random copolymer that contains only annealed units, weak acid and weak base. The “semiannealed” polyampholyte consists of the mixture of annealed (weak acid) and quenched (quaternized segment) units. Polyampholyte brushes with various grafting densities are synthesized and carefully characterized using surface techniques such as ellipsometry and FTIR‐ATR. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4305–4319, 2008     

Facile synthesis of well‐defined pH‐liable Schiff‐base‐type photosensitive polymers via visible‐light‐activated ambient temperature RAFT polymerization

Inspired by the structure character and photosensitive molecular mechanism of natural rhodopsin or bacteriorhodopsin, a novel pH‐liable photosensitive polymer whose chromophores directly bind with Schiff base linkages was designed. Accordingly, 2‐((3‐phenylallylidene)amino)ethyl methacrylate (PAAEMA), 2‐((3‐(4‐fluorophenyl)allylidene)amino)ethyl methacrylate (FPAAEMA), and 2‐((3‐(4‐methoxyphenyl)allylidene)amino)ethyl methacrylate (MPAAEMA) monomers were synthesized. These monomers were polymerized upon irradiating with mild visible light at ambient temperature. The results indicate that Schiff base linkages of these monomers are stable under such mild polymerizing conditions, and the weak absorption of dithioester functionalities in the visible wave range leads to a rapid and well‐controlled RAFT polymerization. The polymerization rate slows down but initialization period significantly shortens on increasing the feed molar ratio of monomer. The pendant electron‐withdrawing‐group‐substituted chromophore improves the reactivity of monomer, but electron‐donating‐group‐substituted chromophore significantly inactivates monomer. Glycidyl methacrylate (GMA) may well incorporate in this polymer via RAFT random copolymerization of PAAEMA and GMA monomers due to the comparable reactivity ratios of this monomer pair. PolyMPAAEMA exhibits reversible fluorescence emitting or quenching upon deprotonating or protonating the Schiff base linkages. This fluorescence behavior may be of interest in the fabrication of pH‐responsive photosensors, light modulators, or actuators. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6668–6681, 2009     

SET‐RAFT of MMA mediated by ascorbic acid‐activated copper oxide

In this work, cupric oxide (CuO) or cuprous oxide (Cu₂O) was used as the catalyst for the single electron transfer‐reversible addition‐fragmentation chain transfer (SET‐RAFT) polymerization of methyl methacrylate in the presence of ascorbic acid at 25 °C. 2‐Cyanoprop‐2‐yl‐1‐dithionaphthalate (CPDN) was used as the RAFT agent. The polymerization occurred smoothly after an induction period arising from the slow activation of CuO (or Cu₂O) and the “initialization” process in RAFT polymerization. The polymerizations conveyed features of “living”/controlled radical polymerizations: linear evolution of number‐average molecular weight with monomer conversion, narrow molecular weight distribution, and high retention of chain end fidelity. From the polymerization profile, it was deduced that the polymerization proceeded via a conjunct mechanism of single electron transfer‐living radical polymerization (SET‐LRP) and RAFT polymerization, wherein CPDN acting as the initiator for SET‐LRP and chain transfer agent for RAFT polymerization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and characterization of fluorescently labeled core cross‐linked star polymers

A series of fluorescently labeled core cross‐linked star (CCS) polymers were synthesized via the “arm‐first” approach, employing atom transfer radical polymerization (ATRP) to control the resulting architecture. The initiator p‐toluenesulfonyl chloride (TsCl) was used to synthesize “living” poly(methyl methacrylate) (PMMA) macroinitiator, which was subsequently cross‐linked to generate the CCS polymers. Divinylbenzene (DVB) was used as the cross‐linker and 7‐[4‐(trifluoromethyl)coumarin] methacrylamide ( F₁ , λ_ex = 343 nm) was added as a fluorescent labeling monomer. A range of PMMA/DVB/ F₁ based CCS polymers were synthesized with the core domain made selectively fluorescent by using varying amounts of monomer F₁ . The core functionalized stars were characterized using gel permeation chromatography (GPC) equipped with multi‐angle laser light scattering (MALLS), refractive index (RI), and UV–visible detectors. The fluorescence quantum yield (Φ_F) and the amount of fluorescent monomer incorporated into the core were quantified by UV–visible and fluorescence spectrophotometry. It was recognized that the overall molecular weights of the stars produced, along with their core molecular weight, decreased as the mol % of monomer F₁ was increased relative to cross‐linker. Visual confirmation of F₁ incorporation was obtained by fluorescence microscopy of thin polymer films cast on glass substrates. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2422–2432, 2008     

Surface grafting onto SiC nanoparticles with glycidyl methacrylate in emulsion

To improve the tribological performance of nano‐SiC particles filled epoxy composites, surface modification of the fillers is necessary. By means of soapless emulsion polymerization method, graft polymerization of glycidyl methacrylate (GMA) onto the surface of alkyl nano‐SiC was carried out, resulting in composite particles with SiC core and polymeric shell in which polyglycidyl methacrylate (PGMA) is chemically attached to the nanoparticles by the double bonds introduced during the pretreatment with a coupling agent. By analyzing the reaction mechanism, the emulsion polymerization loci were found to be situated at the SiC surface. Also, the factors affecting the grafting yielding of PGMA on the particles were investigated, including monomer concentration, initiator consumption, reaction temperature, reaction time, etc. Accordingly, an optimum grafting reaction condition was determined. It was shown that the grafted nanoparticles exhibit greatly improved dispersibility in good solvent for the grafting polymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3842–3852, 2004     

Polyiodized‐PCL as multisite transfer agent: Towards an enlarged library of degradable graft copolymers

Poly(ε‐caprolactone)‐based graft copolymers were prepared via a “grafting from” technique derived from iodine transfer polymerization. This copolymerization was done thanks to a poly(ε‐caprolactone‐co‐α‐iodo‐ε‐caprolactone) (PCL‐I), which was used as a multisite transfer agent. Styrene (Sty) and n‐butyl acrylate (n‐BuA) were firstly used as model monomers to establish the feasibility of using PCL‐I as multisite transfer agent, and investigate some general properties of the polymerization. The formation of PCL‐g‐PSty and PCL‐g‐P(n‐BuA) copolymers was confirmed by SEC and NMR analyzes of the copolymers before and after degradation of the PCL backbone. This method was extended to an acrylamide monomer, namely (N,N‐dimethyl) acrylamide (DMA), to prepare original amphiphilic copolymers with PCL as hydrophobic backbone and amido‐functionalized hydrophilic grafted chains. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5006–5016, 2009     

AGET ATRP of water‐soluble PEGMA: Fast living radical polymerization mediated by iron catalyst

In this work, living radical polymerizations of a water‐soluble monomer poly(ethylene glycol) monomethyl ether methacylate (PEGMA) in bulk with low‐toxic iron catalyst system, including iron chloride hexahydrate and triphenylphosphine, were carried out successfully. Effect of reaction temperature and catalyst concentration on the polymerization of PEGMA was investigated. The polymerization kinetics showed the features of “living”/controlled radical polymerization. For example, M_n,GPC values of the resultant polymers increased linearly with monomer conversion. A faster polymerization of PEGMA could be obtained in the presence of a reducing agent Fe(0) wire or ascorbic acid. In the case of Fe(0) wire as the reducing agent, a monomer conversion of 80% was obtained in 80 min of reaction time at 90 °C, yielding a water‐soluble poly(PEGMA) with M_n = 65,500 g mol^?1 and M_w/M_n = 1.39. The features of “living”/controlled radical polymerization of PEGMA were verified by analysis of chain‐end and chain‐extension experiments. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Aqueous RAFT polymerization of 2‐aminoethyl methacrylate to produce well‐defined,primary amine functional homo‐ and copolymers

We report the direct homopolymerization and block copolymerization of 2‐aminoethyl methacrylate (AEMA) via aqueous reversible addition‐fragmentation chain transfer (RAFT) polymerization. The controlled “living” polymerization of AEMA was carried out directly in aqueous buffer using 4‐cyanopentanoic acid dithiobenzoate (CTP) as the chain transfer agent (CTA), and 2,2′‐azobis(2‐imidazolinylpropane) dihydrochloride (VA‐044) as the initiator at 50 °C. The controlled “living” character of the polymerization was verified with pseudo‐first order kinetic plots, a linear increase of the molecular weight with conversion, and low polydispersities (PDIs) (<1.2). In addition, well‐defined copolymers of poly(AEMA‐b‐HPMA) have been prepared through chain extension of poly(AEMA) macroCTA with N‐(2‐hydroxypropyl)methacrylamide (HPMA) in water. It is shown that the macroCTA can be extended in a controlled fashion resulting in near monodisperse block copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5405–5415, 2009