Polymer brushes on multiwalled carbon nanotubes by activators regenerated by electron transfer for atom transfer radical polymerization

The synthesis and characterization of multiwalled carbon nanotube (MWCNT) polymer brushes produced by activators regenerated by electron transfer (ARGET) in atom‐transfer radical polymerization (ATRP) was discussed. The polymer brushes were synthesized by esterification of the MWCNT carboxylic acid groups with hydroxyethyl‐2‐bromoisobutyrate and subsequently used in ARGET ATRP. This created a well defined living polymer brush carbon nanotube of comparatively low polydispersity and a polymer layer 10 nm thick. As, ARGET ATRP uses only minute concentrations of copper (II) catalyst, and is less sensitive to air compared to other living polymerization techniques, this process is a more industry‐compatible route for the commercialization of such materials. The structural and chemical properties were explored by a range of techniques including high resolution transmission electron microscopy, gel permeation chromatography, elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. In addition, the polymer brush nanotubes were explored for their potential use in films and as fillers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Atom transfer radical polymerization with activators regenerated by electron transfer of acrylonitrile from silica nanoparticles,and adsorption properties of the resin for Hg2+ after amidoximation with hydroxylamine

Polyacrylonitrile (PAN) was grafted from surfaces of chloro‐modified silica‐gel with their surface chlorines as initiation sites, using an iron (III)‐mediated surface‐initiated atom transfer radical polymerization (ATRP) with activators regenerated by electron transfer (SI‐ARGET ATRP) method. The graft reaction exhibits first‐order kinetics with respect to the polymerization time in the low‐monomer‐conversion stage. The conversion of monomer (C%) and the percentage of grafting (PG%) increased with increasing of the polymerizing time and reached 23 and 730% after a polymerizing time of 24 hr, respectively. Hydroxylamine (NH₂OH·HCl) was used to modify the cyano groups of SG‐g‐PAN to obtain amidoxime (AO) groups. The AO SG‐g‐PAN was used to remove Hg²⁺. The adsorption kinetics indicated that the pseudo‐second‐order model was more suitable to describe the adsorption kinetics of AO SG‐g‐PAN for Hg²⁺. The adsorption isotherms demonstrated that Langmuir model was much better than Freundlich model to describe the isothermal process. Copyright © 2010 John Wiley & Sons, Ltd.     

通过原子转移自由基聚合合成可光交联的聚苯乙烯接枝共聚物

聚苯乙烯(PS)在氯化锌(ZnCl_2)做催化剂下,通过氯甲基甲基醚氯甲基化反应,合成了氯甲基化聚苯乙烯(CMPS).在氯化亚铜/联二吡啶(CuCl/bpy)催化下,以CMPS为大分子引发剂引发甲基丙烯酸甲酯(MMA)、甲基丙烯酸酯化查尔酮(MSPK)进行原子转移自由基聚合,成功合成了侧链含有查尔酮结构的光敏聚苯乙烯接枝共聚物(PSMM),所得聚合物结构经过红外光谱(FT-IR)、核磁共振氢谱(~1H NMR)得到确认,通过热重分析(TG)、示差扫描量热法(DSC)测试了该聚合物的热学性能.结果表明,该接枝共聚物具有较好的热学性能及良好的光敏性.     

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     

Growth of poly(methyl methacrylate) brushes on silicon surfaces by atom transfer radical polymerization

Poly(methyl methacrylate) (PMMA) brushes are grown by surface‐initiated atom transfer radical polymerization on silicon surfaces at various polymerization temperatures. Kinetic studies show that the layer thickness scales linearly with the degree of polymerization of the polymers under some conditions, indicating a constant graft density of the surface‐attached chains. At high temperatures, the layer growth is a controlled process only for short reaction times, and after a rapid increase, the film growth levels off, and a constant thickness is obtained. At lower reaction temperatures, polymers with a lower polydispersity are obtained, but at the expense of a much slower growth rate. Accordingly, intermediate temperatures yield the highest film thickness on experimentally feasible timescales. The reinitiation of these surface‐grafted PMMA chains at room temperature to either extend the chains or grow a chemically different polyglycidylmethacrylate block demonstrates the presence of active ends and the living nature of the surface‐grafted PMMA chains. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1758–1769, 2006     

A novel approach to modify poly(vinylidene fluoride) via iron‐mediated atom transfer radical polymerization using activators generated by electron transfer

Iron‐mediated atom transfer radical polymerization using activators generated by electron transfer directly from the secondary fluorine atoms on the poly(vinylidene fluoride) (PVDF) backbone, using methyl methacrylate (MMA) and poly (ethylene glycol) methyl ether methacrylate (PEGMA) as the monomers, FeCl₃·6H₂O as the catalyst, PPh₃ as the ligand, and vitamin C as the reducing agent, was demonstrated in the presence of limited amounts of air. The successful syntheses of the corresponding graft copolymers PVDF‐g‐PMMA and PVDF‐g‐PPEGMA were characterized by nuclear magnetic resonance, Fourier transform infrared and X‐ray photoelectron spectroscopy, respectively. The graft copolymers PVDF‐g‐PPEGMA can be readily cast into porous hydrophilic microfiltration membranes by phase inversion in an aqueous medium. The morphologies were characterized by scanning electron microscopy. The surface and bulk hydrophilicity were evaluated on the basis of static water contact angle and the steady adsorption of bovine serum albumin. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

PMMA‐grafted dextran glycopolymers by atom transfer radical polymerization

The four‐step synthesis of amphiphilic glycopolymers associating dextran as backbone and poly(methyl methacrylate) (PMMA) as grafts is reported, using the “grafting from” strategy. In the first step, the dextran OH functions were partially acetylated. The second step consisted in linking initiator groups by reaction of 2‐bromoisobutyryl bromide (BⁱBB) with the unprotected OH functions. Third, the atom transfer radical polymerization (ATRP) of methyl methacrylate was carried out in DMSO from the resulting dextran derivative used as a macroinitiator. Finally, the cleavage of the acetate groups led to the expected glycopolymers. Careful attention was given both to the copolymer structure and the control of polymerization. PMMA grafts were analyzed by SEC‐MALLS after their deliberate cleavage from the backbone to evidence a controlled polymerization. Moreover, the mildness of the final deprotection conditions was proved to ensure acetate cleavage without either degrading dextran backbone and PMMA grafts or cleaving grafts from dextran backbone. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7606–7620, 2008     

Attapulgite grafted with polystyrene via a simultaneous reverse and normal initiation atom transfer radical polymerization

The surface grafting of attapulgite (ATP) with polystyrene (PS) was established via a simultaneous reverse and normal initiation atom transfer radical polymerization (SR&NIATRP). 4‐(chloromethyl)phenyltrimethoxysilane (CMPTMS) chemical bounded on the surface of ATP (ATP‐Cl, Cl‐I) was prepared via one‐step self‐assembly. SR&NI ATRP of styrene was conducted using CuCl₂ complex tris(2‐(dimethylamino)ethyl)amine (Me₆‐TREN) as the catalytic system, initiated by 2,2‐azobis(isobutyronitrile) (AIBN) and ATP‐Cl. FT‐IR, XRD, XPS, TGA and TEM data were consistent with the grafting of benzyl chloride groups and PS chains on ATP surface. The controllability of polymerization was investigated by the kinetics behavior under different molar ratio of AIBN and CuCl₂. The obtained polymer possessed a uniform distribution of molecular weights with a lower polydispersity index of 1.2～1.4. The relationship between polymerization on the surface of ATP and in solution was discussed in detail based on TGA data of hybrid particles and GPC trace of free polymer in solution. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1508–1516     

Atom transfer radical polymerization using activators regenerated by electron transfer of acrylonitrile in 1‐(1‐ethoxycarbonylethyl)‐3‐methylimidazolium hexafluorophospate

Atom transfer radical polymerization using activators regenerated by electron transfer (ARGET ATRP) of acrylonitrile (AN) was first approached with 1‐(1‐ethoxycarbonylethyl)‐3‐methylimidazolium tetrafluoroborate ([ecemim][BF₄]) as reaction medium and tin(II) bis(2‐ethylhexanoate) (Sn(EH)₂) as reducing agent in the presence of air. When compared with in bulk, an obvious increase of polymer isotacticity was observed for ARGET ATRP of AN in 1‐(1‐ethoxycarbonylethyl)‐3‐methylimidazolium hexafluorophospate ([ecemim][PF₆]), the reaction rate of ARGET ATRP of AN in [ecemim][PF₆] was higher and the polymerization process was better controlled. The block copolymer polyacrylonitrile‐block‐poly(methyl methacrylate) with molecular weight at 69,750, distribution at 1.34, and isotacticity at 0.36 was successfully obtained in [ecemim][PF₆]. [Ecemim][PF₆] and the catalyst system were recycled and reused and had no effect on the living nature of polymerization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Polymer coating of graphene oxide via reversible addition–fragmentation chain transfer mediated emulsion polymerization

This work describes a versatile method to encapsulate graphene oxide (GO) with polymers using reversible addition‐fragmentation chain transfer (RAFT) mediated emulsion polymerization. A living low molecular weight anionic macro‐RAFT statistical copolymer of sodium styrene sulfonate, acrylic acid, and butyl acrylate (BA) was synthesized using 2‐{[(butylsulfanyl)carbonothioyl] sulfanyl} propanoic acid as the chain transfer agent. GO was dispersed in water by pretreating the surface with poly(allylamine hydrochloride) (PAH), before being stabilized by the addition of the anionic macro‐RAFT copolymer. PAH was used to facilitate the adsorption of the macro‐RAFT copolymer to the GO surface via electrostatic attraction between opposite charges. The dispersed GO sheets were encapsulated with polymer by the free radical emulsion polymerization of methyl methacrylate and BA under starved fed conditions. The polymer shells encapsulating the GO sheets were formed by the chain extension of the adsorbed living macro‐RAFT copolymer. TEM, SEM, FTIR, and AFM were used to confirm the presence of the polymer layer on the surface of the GO. The thickness of the polymer coating can be adjusted by controlling the amount of monomer fed into the system. Partial polymer coatings of the GO could be achieved by varying the amount of PAH. The encapsulated GO was found to be easily dispersed in both aqueous and organic solvents over a range of polarities. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1413–1421     

Synthesis of well‐defined hairy polymer microspheres by precipitation polymerization and surface‐initiated atom transfer radical polymerization

A variety of polymer microspheres were successfully synthesized by the surface‐initiated atom transfer radical polymerization (SI‐ATRP) of monomers by using monodisperse polymer microsphere having benzyl halide moiety as a multifunctional polymeric initiator. First, a series of monodisperse polymer microsphere having benzyl chloride with variable monomer ratio (P(St‐DVB‐VBC)) were synthesized by the precipitation polymerization of styrene (St), divinylbenzene (DVB), and 4‐vinylbenzyl chloride (VBC). Next, hairy polymer microspheres were synthesized by the surface‐initiated ATRP of various monomers with P(St‐DVB‐VBC) microsphere as a multifunctional polymeric initiator. The hair length determined by the SEC analysis of free polymer was increased with the increase of M/I. These hairy polymer microspheres were characterized by SEM, FT‐IR, and Cl content measurements. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1296–1304     

Synthesis of PNIPAM polymer brushes on reduced graphene oxide based on click chemistry and RAFT polymerization

Preparation and characterization of poly(N‐isopropylacrylamide) (PNIPAM) polymer brushes on the surfaces of reduced graphene oxide (RGO) sheets based on click chemistry and reversible addition‐fragmentation chain transfer (RAFT) polymerization was reported. RGO sheets prepared by thermal reduction were modified by diazonium salt of propargyl p‐aminobenzoate, and alkyne‐functionalized RGO sheets were obtained. RAFT chain transfer agent (CTA) was grafted to the surfaces of RGO sheets by click reaction. PNIPAM on RGO sheets was prepared by RAFT polymerization. Fourier transform‐infrared spectroscopy, thermogravimetric analysis, X‐ray photoelectron spectroscopy, and transmission electron microscopy (TEM) results all demonstrated that RAFT CTA and PNIPAM were successfully produced on the surfaces of RGO sheets. Nanosized PNIPAM domains on RGO sheets were observed on TEM. Micro‐DSC result indicated that in aqueous solution PNIPAM on RGO sheets presented a lower critical solution temperature at 33.2 °C. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Graft polymerization of polysilsesquioxane containing chloromethylphenyl groups by atom transfer radical polymerization

Polysilsesquioxane with phenyl and chloromethylphenyl groups (PCPSQ) was prepared readily from phenyltrimethoxysilane and [2‐(chloromethylphenyl)ethyl]trimethoxysilane under acidic conditions. Polymerization with chloromethylphenyl groups on PCPSQ with methyl methacrylate (MMA) was conducted in the presence of a catalytic amount of copper(I) bromide and (−)‐sparteine. Atom transfer radical polymerization yielded a graft polymer (PCPSQ‐g‐MMA) efficiently, and no gelation was observed. The process was also applied to the preparation of graft block copolymers on PCPSQ with several methacrylate monomers. An advantage of the graft hybrid polymers was shown in improved thermal behavior. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4212–4221, 2004     

Synthesis of well‐defined polymer brushes on the surface of zinc antimonate nanoparticles through surface‐initiated atom transfer radical polymerization

Zinc antimonate nanoparticles consisting of antimony and zinc oxide were surface modified in a methanol solvent medium using triethoxysilane‐based atom transfer radical polymerization (ATRP) initiating group (i.e.,) 6‐(2‐bromo‐2‐methyl) propionyloxy hexyl triethoxysilane. Successful grafting of ATRP initiator on the surface of nanoparticles was confirmed by thermogravimetric analysis that shows a significant weight loss at around 250–410 °C. Grafting of ATRP initiator onto the surface was further corroborated using Fourier transform Infrared spectroscopy (FT‐IR) and X‐ray photoelectron spectroscopy (XPS). The surface‐initiated ATRP of methyl methacrylate (MMA) mediated by a copper complex was carried out with the initiator‐fixed zinc antimonate nanoparticles in the presence of a sacrificial (free) initiator. The polymerization was preceded in a living manner in all examined cases; producing nanoparticles coated with well defined poly(methyl methacrylate) (PMMA) brushes with molecular weight in the range of 35–48K. Furthermore, PMMA‐grafted zinc antimonate nanoparticles were characterized using Thermogravimetric analysis (TGA) that exhibit significant weight loss in the temperature range of 300–410 °C confirming the formation of polymer brushes on the surface with the graft density as high as 0.26–0.27 chains/nm². The improvement in the dispersibility of PMMA‐grafted zinc antimonate nanoparticles was verified using ultraviolet‐visible spectroscopy and transmission electron microscopy. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis of miktoarm star and miktoarm star block copolymers via a combination of atom transfer radical polymerization and stable free‐radical polymerization

A trifunctional initiator, 2‐phenyl‐2‐[(2,2,6,6‐tetramethyl)‐1‐piperidinyloxy] ethyl 2,2‐bis[methyl(2‐bromopropionato)] propionate, was synthesized and used for the synthesis of miktoarm star AB₂ and miktoarm star block AB₂C₂ copolymers via a combination of stable free‐radical polymerization (SFRP) and atom transfer radical polymerization (ATRP) in a two‐step or three‐step reaction sequence, respectively. In the first step, a polystyrene (PSt) macroinitiator with dual ω‐bromo functionality was obtained by SFRP of styrene (St) in bulk at 125 °C. Next, this PSt precursor was used as a macroinitiator for ATRP of tert‐butyl acrylate (tBA) in the presence of Cu(I)Br and pentamethyldiethylenetriamine at 80 °C, affording miktoarm star (PSt)(PtBA)₂ [where PtBA is poly(tert‐butyl acrylate)]. In the third step, the obtained St(tBA)₂ macroinitiator with two terminal bromine groups was further polymerized with methyl methacrylate by ATRP, and this resulted in (PSt)(PtBA)₂(PMMA)₂‐type miktoarm star block copolymer [where PMMA is poly(methyl methacrylate)] with a controlled molecular weight and a moderate polydispersity (weight‐average molecular weight/number‐average molecular weight < 1.38). All polymers were characterized by gel permeation chromatography and ¹H NMR. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2542–2548, 2003     

Generation of core/shell iron oxide magnetic nanoparticles with polystyrene brushes by atom transfer radical polymerization

The functionalization of nanoparticle surfaces is required to improve the dispersion of an inorganic material inside an organic matrix. In this work, polystyrene (PS) brushes were grown on the surface of iron oxide magnetic nanoparticles with atom transfer radical polymerization and a grafting‐from approach. After polymerization, the magnetic nanoparticles had a graft density of 0.9 PS chains/nm². A sacrificial initiator was used to obtain a satisfactory result for the control of the polymerization, as its addition had to generate a sufficient concentration of persistent radicals (deactivator). A variety of techniques, such as Fourier transform infrared spectroscopy, thermogravimetric analysis, gel permeation chromatography, water contact‐angle measurements, and atomic force microscopy, were used to characterize the nanoparticles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4744–4750, 2007     

Functionalization of iron oxide magnetic nanoparticles with poly(methyl methacrylate) brushes via grafting‐from atom transfer radical polymerization

A key problem with nanomaterials is the difficulty of controlling the dispersion of nanoparticles inside an organic medium. To overcome this problem, functionalization of the nanoparticle surface is required. Poly(methyl methacrylate) (PMMA) brushes were grown on the surface of iron oxide magnetic nanoparticles with atom transfer radical polymerization and a grafting‐from approach. Modified magnetic nanoparticles with a graft density of 0.1 PMMA chains/nm² were obtained. Cu(II), used as a deactivating complex, allowed good control of the polymerization along with a narrow polydispersity of the polymer chains. The functionalized magnetic nanoparticles were characterized with Fourier transform infrared spectroscopy, thermogravimetric analysis, gel permeation chromatography, and atomic force microscopy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 925–932, 2007     

Stimuli‐responsive diblock copolymer brushes via combination of “click chemistry” and living radical polymerization

pH‐ and temperature‐responsive poly(N‐isopropylacrylamide‐block?4‐vinylbenzoic acid) (poly(NIPAAm‐b‐VBA)) diblock copolymer brushes on silicon wafers have been successfully prepared by combining click reaction, single‐electron transfer‐living radical polymerization (SET‐LRP), and reversible addition‐fragmentation chain‐transfer (RAFT) polymerization. Azide‐terminated poly(NIPAAm) brushes were obtained by SET‐LRP followed by reaction with sodium azide. A click reaction was utilized to exchange the azide end group of a poly(NIPAAm) brushes to form a surface‐immobilized macro‐RAFT agent, which was successfully chain extended via RAFT polymerization to produce poly(NIPAAm‐b‐VBA) brushes. The addition of sacrificial initiator and/or chain‐transfer agent permitted the formation of well‐defined diblock copolymer brushes and free polymer chains in solution. The free polymer chains were isolated and used to estimate the molecular weights and polydispersity index of chains attached to the surface. Ellipsometry, contact angle measurements, grazing angle‐Fourier transform infrared spectroscopy, and X‐ray photoelectron spectroscopy were used to characterize the immobilization of initiator on the silicon wafer, poly(NIPAAm) brush formation via SET‐LRP, click reaction, and poly(NIPAAm‐b‐VBA) brush formation via RAFT polymerization. The poly(NIPAAm‐b‐VBA) brushes demonstrate stimuli‐responsive behavior with respect to pH and temperature. The swollen brush thickness of poly(NIPAAm‐b‐VBA) brush increases with increasing pH, and decreases with increasing temperature. These results can provide guidance for the design of smart materials based on copolymer brushes. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2677–2685     

Coupled atom transfer radical coupling and atom transfer radical polymerization approach for controlled grafting from poly(vinylidene fluoride) backbone

A new “grafting from” strategy for grafting of different monomers (methacrylates, acrylates, and acrylamide) on poly(vinylidene fluoride) (PVDF) backbone is designed using atom transfer radical coupling (ATRC) and atom transfer radical polymerization (ATRP). 4‐Hydroxy TEMPO moieties are anchored on PVDF backbone by ATRC followed by attachment of ATRP initiating sites chosen according to the reactivity of different monomers. High graft conversion is achieved and grafting of poly(methyl methacrylate) (PMMA) exhibits high degree of polymerization (DPn = 770) with a very low graft density (0.18 per hundred VDF units) which has been increased to 0.44 by regenerating the active catalyst with the addition of Cu(0). A significant impact on thermal and stress–strain property of graft copolymers on the graft density and graft length is noted. Higher tensile strain and toughness are observed for PVDF‐g‐PMMA produced from model initiator but graft copolymer from pure PVDF exhibits higher tensile strength and Young's modulus. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 995–1008     

Preparation of polymer‐grafted carbon black nanoparticles by surface‐initiated atom transfer radical polymerization

Pristine carbon black was oxidized with nitric acid to produce carboxyl group, and then the carboxyl group was consecutively treated with thionyl chloride and glycol to introduce hydroxyl group. The hydroxyl group on the carbon black surface was reacted with 2‐bromo‐2‐methylpropionyl bromide to anchor atom transfer radical polymerization (ATRP) initiator. The ATRP initiator on carbon black surface was verified by TGA, FTIR, EDS, and elemental analysis. Then, poly (methyl methacrylate) and polystyrene chains were respectively, grown from carbon black surface by surface‐initiated atom transfer radical polymerization (SI‐ATRP) using CuCl/2,2‐dipyridyl (bpy) as the catalyst/ligand combination at 110 °C in anisole. ¹H NMR, TGA, TEM, AFM, DSC, and DLS were used to systemically characterize the polymer‐grafted carbon black nanoparticles. Dispersion experiments showed that the grafted carbon black nanoparticles had good solubilities in organic solvents such as THF, chloroform, dichloromethane, DMF, etc. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3451–3459, 2007