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Hyperbranched poly(glycidyl methacrylate) (PGMA) and poly(GMA-co-styrene) have been synthesized by the self-condensing vinyl polymerization of GMA and the copolymerization of GMA and St. Cp₂Ti(III)Cl catalyzed the epoxy groups to produce initiating radicals and Cu(II)X₂ (X = Br or Cl) was used for control of the polymerization. The resultant polymers were characterized by GPC and ¹H NMR, and the molecular weights, the molecular weight distribution and the degree of branching were determined. The branching structure of the polymers was further confirmed by a hydrolysis test. Hyperbranched star polymers with HPGMA as the core and PSt as the arms were synthesized by the atom transfer radical polymerization of St using HPGMA as a macroinitiator. The resultant products were analyzed by GPC and ¹H NMR. Their morphology in solution was investigated by TEM. The hyperbranched polymers were modified by various acids and amines, and the variation in solution properties was investigated.

Heteroarm H-shaped terpolymers, [(poly(L-lactide))(polystyrene)]poly(ethylene oxide)[(polystyrene)(poly(L-lactide))], [(PLLA)(PS)]PEO[(PS)(PLLA)], in which PEO acts as a main chain and PS and PLLA as side arms, have been successfully prepared via combination of reversible addition–fragmentation transfer (RAFT) polymerization and ring-opening polymerization (ROP). The first step is the synthesis of the PEO capped with one terminal dithiobenzoate group and one hydroxyl group at every chain end, [(HOCH₂)(PhC(S)S)]PEO[(S(S)CPh)(CH₂OH)] from the reaction of carboxylic acid with ethylene oxide. Then, the RAFT polymerization of styrene (St) was carried out using [(HOCH₂)(PhC(S)S)]PEO[(S(S)CPh)(CH₂OH)] as RAFT agent and AIBN as initiator, and the triblock copolymer, [(HOCH₂)(PS)]PEO[(PS)(CH₂OH)], was formed. Finally, the heteroarm H-shaped terpolymers, [(PLLA)(PS)]PEO[(PS)(PLLA)], were produced by ROP of LLA, using triblock copolymer, [(HOCH₂)(PS)]PEO[(PS)(CH₂OH)], as macroinitiator and Sn(Oct)₂ as catalyst. The target products and intermediates were characterized by ¹H NMR spectroscopy and gel permeation chromatography. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 789–799, 2007

Poly(ethylene oxide) (PEO) star microgels with a cross-linked polystyrene core were successfully prepared by reversible addition-fragmentation transfer polymerization of styrene (St) and divinylbenzene (DVB) with dithiobenzoate-terminated PEO monomethyl ether (DTB-MPEO) as macro chain transfer agent in mixtures of ethanol and tetrahydrofuran (THF). The formation of star polymers was affected by polymerization time, solvents and St:DVB:DTB-MPEO molar ratios. Narrow polydispersed star microgels with high molecular weight were obtained under appropriate polymerization conditions. Transmission electron micrographs suggest that PEO star polymers could form nano-size spherical micelles in mixtures of water and THF, which further demonstrates the amphiphilic nature of the star polymers. Copyright © 2006 Society of Chemical Industry

Polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) was synthesized by two steps of reversible addition-fragmentation transfer (RAFT) polymerization of styrene (St) and 4-vinylpyridine (4VP) successively. After P4VP block was quaternized with CH₃I, PS-b-quaternized P4VP/montmorillonite (PS-b-QP4VP/MMT) nanocomposites were prepared by cationic exchange reactions of quaternary ammonium ion in the PS-b-QP4VP with ions in MMT. The results obtained from X-ray diffraction (XRD) and transmission electron microscopy (TEM) images demonstrate that the block copolymer/MMT nanocomposites are of intercalated and exfoliated structures, and also a small amount of silicates' layers remained in the original structure; differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) results show that the nanocomposites displayed higher glass transition temperature (T_g) and higher thermal stability than that of the corresponding copolymers. The blending of PS-b-QP4VP/MMT with commercial PS makes MMT to be further separated, and the MMT was homogeneously dispersed in the polymer matrix. The enhancement of thermal stability of PS/PS-b-QP4VP/MMT is about 20°C in comparison with commercial PS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:1950–1958, 2006

Summary: A double comb-shaped water soluble copolymer, poly[poly(ethylene oxide) methyl ether methacrylate]-block-poly(N-isopropylacrylamide)-block-poly[poly (ethylene oxide) methyl ether methacrylate], abbreviated as [P(MA-MPEO)-block-PNIPAM-block-P(MA-MPEO)], with a controlled molecular weight and narrow polydispersity was successively synthesized using a macromonomer technique. The ⁶⁰Co γ irradiation polymerization of MA-MPEO in the presence of dibenzyl trithiocarbonate (DBTTC) at room temperature afforded a polymer, P(MA-MPEO)-SC(S)S-P(MA-MPEO), which was subsequently used as a macro RAFT agent in the RAFT polymerization of N-isopropylacrylamide, and water soluble double comb-shaped copolymers, P(MA-MPEO)-block-PNIPAM-block-P(MA-MPEO), were successfully obtained.

Summary: Stable micelles with polystyrene (PS) as a shell and cross-linked poly[(acrylic acid)-co-(ethylene glycol diacrylate)] as a core have been successfully prepared by reversible addition fragmentation chain transfer (RAFT) copolymerization of acrylic acid and ethylene glycol diacrylate in a selective solvent with PS-SC(S)Ph as a RAFT agent. For the preparation of stable micelles, the RAFT polymerizations are carried out in different solvents: benzene, cyclohexane, and mixtures of tetrahydrofuran and cyclohexane. The monomer/PS-SC(S)Ph molar ratio and molecular weight of the macro-RAFT agent, PS-SC(S)Ph, influence the RAFT polymerization and the formation of micelles.

A well-defined branched copolymer with PLLA-b-PS₂ branches was prepared by combination of reversible addition-fragmentation transfer (RAFT) polymerization, ring-opening polymerization (ROP), and atom transfer radical polymerization (ATRP). The RAFT copolymerization of methyl acrylate (MA) and hydroxyethyl acrylate (HEA) yielded poly(MA-co-HEA), which was used as macro initiator in the successive ROP polymerization of LLA. After divergent reaction of poly(MA-co-HEA)-g-PLLAOH with divergent agent, the macro initiator, poly(MA-co-HEA)-g-PLLABr₂ was formed in high conversion. The following ATRP of styrene (St) produced the target polymer, poly(MA-co-HEA)-g-(PLLA-b-PS₂). The structures, molecular weight, and molecular weight distribution of the intermediates and the target polymers obtained from every step were confirmed by their ¹H NMR and GPC measurements. DSC results show one T = 3 °C for the poly(MA-co-HEA), T = −5 °C, T= 122 °C, and T = 157 °C for the branched copolymers (poly(MA-co-HEA)-g-PLLA), and T = 51 °C, T = 116 °C, and T = 162 °C for poly(MA-co-HEA)-g-(PLLA-b-PS₂). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 549–560, 2006

Novel hyperbranched poly(amido amine)s containing tertiary amines on the backbones and acryl or secondary amines as the surface groups were successfully synthesized via the Michael addition polymerizations of a triacrylamide [1,3,5-triacryloylhexahydro-1,3,5-triazine (TT)] and a difunctional amine [n-butylamine (BA)] NMR techniques were used to clarify the structures of hyperbranched polymers and polymerization mechanism. The reactivity of the secondary amine formed in situ was much lower than that of the primary amines in BA. When the feed molar ratio was 1:1 TT/BA, the secondary amine formed in situ was almost kept out of the reaction before the BA (AA′) and TT (B₃) monomers were consumed, and this led to the formation of A′B₂ intermediates containing one secondary amine group and two acryl groups. The self-polymerization of the A′B₂ intermediates produced hyperbranched polymers bearing acryl as surface groups. For the polymerization with the feed molar ratio of 1:2 TT/BA, A′₂B intermediates containing one acryl group and two secondary amine groups were accumulated until self-polymerization started; the self-polymerization of the intermediates formed hyperbranched polymers with secondary amines as their surface groups. Modifications of surface functional groups were studied to form new hyperbranched polymers. The hyperbranched poly(amido amine)s were amorphous. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6226–6242, 2006

Summary: Bio-affinitive, nanosized polymeric micelles with glucosamine in their corona have a specific interaction with Concanavalin A. They are prepared by a substitution reaction of p-nitrophenol groups in the poly(p-nitrophenyl acrylate) (PNPA) corona of stable micelles with glucosamine. The nanosized, stable, and reactive micelles are formed by self-assembly of the diblock copolymer, poly(p-nitrophenyl acrylate)-block-polystyrene (PNPA-b-PSt) in nitromethane, followed by a shell cross-linking reaction. This method may be useful in the preparation of targeted drugs.

Summary: The fabrication of organic crystals into useful forms might play an important role in future electronics technology. A method for fabricating organic crystal rings has been developed. The self-assembly of six-armed poly(methyl methacrylate) with a triphenylene core leads to the formation of pores homogeneously distributed in the polymer film. Because the solubility of this polymer in tetrahydrofuran (THF) is lower than that of 2,3,6,7,10,11-hexamethacrylate triphenylene (HMTP), the holes initially formed and distributed in the polymer film are filled with a THF solution of HMTP. Crystallization nucleation occurs at the edge of holes and HMPT crystals grow at the contact line to form organic crystal rings.

Summary: The mechanisms of the Michael addition polymerization of N-aminoethyl piperazine (AEPZ) with divinyl sulfone (DVS) were clarified based on the reactivity sequence of three different amines in AEPZ: 2° amine in piperazine ring > 1° amine ≫ 2° amine formed in situ. When the feed molar ratio of DVS to AEPZ was 1:1, the polymerization of AB intermediate formed proceeded, and the linear poly(sulfone amine) containing secondary and tertiary amines in the backbones were produced. The linear structure of the product was confirmed by NMR spectra, and the molecular weights, molecular weight distribution, and properties of poly(sulfone amine)s were characterized by GPC, DSC, and TGA.

Novel hyperbranched poly(amido amine)s containing tertiary amines in the backbones and acryl as terminal groups were synthesized via the Michael addition polymerizations of trifunctional amines with twofold molar diacrylamide. The hyperbranched structures of these poly(amido amine)s were verified by ¹³C NMR (INVGATE). The polymerization mechanisms were clarified by following the polymerization process with NMR method, and the results show that the reactivity of secondary amine formed in situ is much lower than that of the secondary amine in 1-(2-aminoethyl) piperazine (AEPZ) ring and the primary amine. The secondary amine formed in situ was almost kept out of the reaction before the primary and secondary amines in AEPZ were consumed, leading to the formation of the AB2 intermediate, and the further reaction of the AB2 yielded the hyperbranched polymers. The molecular weights and properties of poly(amindo amine)s obtained were characterized by GPC, DSC, and TGA, respectively. Based on the reaction of active acryl groups in the polymers obtained with glucosamine, hyperbranched polymers containing sugar were formed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5127–5137, 2005

A new reversible addition-fragmentation chain transfer (RAFT) agent, dendritic polyester with 16 dithiobenzoate terminal groups, was prepared and used in the RAFT polymerization of styrene (St) to produce star polystyrene (PSt) with a dendrimer core. It was found that this polymerization was of living characters, the molecular weight of the dendrimer-star polymers could be controlled and the polydispersities were narrow. The dendrimer-star block copolymers of St and methyl acrylate (MA) were also prepared by the successive RAFT polymerization using the dendrimer-star PSt as macro chain transfer agent. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6379–6393, 2005

Summary: Diblock copolymers, poly(trimethylene oxide)-block-poly(styrene)s abbreviated as poly(TMO)-block-poly(St), and triblock copolymers, poly(TMO)-block-poly(St)-block-poly(MMA)s (MMA = methyl methacrylate), with controlled molecular weight and narrow polydispersity have been successively synthesized by a combination of atom transfer radical polymerization (ATRP) and cationic ring-opening polymerization using the bifunctional initiator, 2-hydroxylethyl α-bromoisobutyrate, without intermediate function transformation. The gel permeation chromatography (GPC) and NMR analyses confirmed the structures of di- and triblock copolymers obtained.

Amphiphilic block comb-shaped copolymers, poly[poly(ethylene oxide) methyl ether acrylate]-block-polystyrene [P(A-MPEO)-block-PSt] with PSt as a handle, were successfully synthesized via a macromonomer technique. The reaction of MPEO with acryloyl chloride yielded a macromonomer, A-MPEO. The macroinitiator PSt capped with the dithiobenzoate group (PSt-SC(S)Ph) was prepared by reversible addition–fragmentation transfer (RAFT) polymerization of styrene in the presence of benzyl dithiobenzoate, and used as macroinitiator in the controlled radical block copolymerization of A-MPEO at room temperature under ⁶⁰Co irradiation. After the unreacted macromonomer A-MPEO had been removed by washing with hot saturated saline water, block comb-shaped copolymers were obtained. Their structure was characterized by ¹H NMR spectroscopy and gel permeation chromatography. The phase transition and self-assembling behaviour were investigated by atomic force microscope and differential scanning calorimetry. Copyright © 2004 Society of Chemical Industry

Poly(p-nitrophenyl acrylate)s (PNPAs) with different molecular mass and narrow polydispersity were successfully synthesized for the first time by reversible addition–fragmentation transfer (RAFT) polymerization with azobisisobutyronitrile (AIBN) as an initiator and [1-(ethoxy carbonyl) prop-1-yl dithiobenzoate] as the chain-transfer agent. Although the molecular mass of PNPAs can be controlled by the molar ratio of NPA to RAFT agent and the conversion, a trace of homo-PNPA was found, especially at the early stage of polymerization. The dithiobenzoyl-terminated PNPA obtained was used as a macro chain-transfer agent in the successive RAFT block copolymerization of styrene (St) with AIBN as the initiator. After purification by two washings with cyclohexane and nitromethane to remove homo-PSt and homo-PNPA, the pure diblock copolymers, PNPA-b-PSt's, with narrow molecular weight distribution were obtained. The structural analysis of polymerization products by ¹H NMR and GPC verified the formation of diblock copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4862–4872, 2004

Well-defined diblock and triblock copolymers composed of poly(N-isopropylacrylamide) (PNIPAM) and poly(ethylene oxide) (PEO) were successfully synthesized through the reversible addition–fragmentation chain transfer polymerization of N-isopropylacrylamide (NIPAM) with PEO capped with one or two dithiobenzoyl groups as a macrotransfer agent. ¹H NMR, Fourier transform infrared, and gel permeation chromatography instruments were used to characterize the block copolymers obtained. The results showed that the diblock and triblock copolymers had well-defined structures and narrow molecular weight distributions (weight-average molecular weight/number-average molecular weight < 1.2), and the molecular weight of the PNIPAM block in the diblock and triblock copolymers could be controlled by the initial molar ratio of NIPAM to dithiobenzoate-terminated PEO and the NIPAM conversion. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4873–4881, 2004

The six-armed polystyrenes and poly(methyl methacrylate)s with a triphenylene core showed different self-assembling patterns, isolated cylinders for polySt on mica and highly ordered cylindrical pores for polyMMA on a silicon wafer. With a decrease of polymer concentration in tetrahydrofuran (THF), the size and height of cylinders decreased for polySt, but for polyMMA, the size and depth of the cylindrical pores increased. Slow evaporation of the solvent and a low molecular weight favored the formation of regular patterns.

The copolymerization of styrene with maleic anhydride (MAh) in the presence of 1-(ethoxycarbonyl)prop-1-yl dithiobenzoate was carried out under UV irradiation at room temperature, and showed ‘living’ polymerization nature which was evidenced by: linear evolution of molecular weight with conversion; and narrow molecular weight distribution (M_w/M_n = 1.08–1.20). The compositional analysis and the sequence structural information of the copolymer obtained from Distortionless Enhancement by Polarization Transfer (DEPT) NMR experiments demonstrated that the copolymers obtained possess strictly alternating structure.

© 2003 Society of Chemical Industry

Cationic polymerization of styrene initiated by the CO⁺ClO group on the surface of expanded graphite (EG) was carried out for modifying the surface properties of graphite. The initiating sites were achieved by the reaction of EG with SOCl₂ and followed by AgClO₄. Subsequently, the cationic polymerization of styrene was conducted to afford polystyrene brush on EG. The influence factors, such as polymerization time and temperature, on the polymerization including the grafting ratio and efficiency were investigated. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2715–2721, 2003

The miktoarm ABC star copolymer with three different branches, polystyrene (PS), poly(1,3-dioxepane) (PDOP), and poly(methyl methacrylate) (PMMA), was successfully prepared. PS with two transfer groups, hydroxyl and dithiobenzoate groups [PS-HECA-SC(S)Ph], was synthesized by the reaction of a dithiobenzoate group at the end of PS with hydroxyethylene cinnamate (HECA) in tetrahydrofuran solution. Then, the cationic ring-opening polymerization of 1,3-dioxepane was initiated by triflic acid in the presence of PS-HECA-SC(S)Ph and diblock copolymer, PS-PDOP, was formed. Finally, the diblock copolymer with the dithiobenzoate group situated between the two blocks was used in the reversible addition–fragmentation transfer (RAFT) process of methyl methacrylate (MMA). The miktoarm ABC star copolymer S(PS)(PDOP)(PMMA) was characterized by ¹H NMR spectroscopy and gel permeation chromatography. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1243–1250, 2003

A new polymerization strategy, consisting of nucleophilic substitution reaction between CS₃^2-, immobilized on a polymeric support, and dimethyl α,α′-dibromoalkylanedioate in solution, leads to the formation of polytrithiocarbonates. When n = 0, 1 in CH₃OOCCHBr(CH₂)_nCHBrCOOCH₃ (α,α′-dibromoalkylanedioate), only five- or six-membered cyclic trithiocarbonates were obtained; n ≥ 2 resulted in the formation of polytrithiocarbonates.

Polymer microspheres were prepared by dispersion copolymerization of styrene with poly(oxyethylene) (peo) macromonomer. A dispersion terpolymerization of styrene, PEO macromonomer and acrylic acid was also conducted to prepare polymer microspheres with both surface carboxyl groups and PEO polymer chains. The microspheres thus obtained were characterized with TEM, IR, and X-ray photoelectron spectroscopy analyses. Palladium nanoparticles were then formed on the surface of these copolymer microspheres forming polymer/metal nanocomposites which were then studied by TEM and X-ray diffraction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2732–2736, 2002

Comb-shaped graft copolymers with poly(methyl methacrylate) as a handle were synthesized by the macromonomer technique in two steps. First, polytetrahydrofuran acrylate (A-PTHF), prepared by the living cationic ring-opening polymerization of tetrahydrofuran, underwent homopolymerization with 1-(ethoxycarbonyl)prop-1-yl dithiobenzoate as an initiator under ⁶⁰Co γ irradiation at room temperature; Second, the handle of the comb-shaped copolymers was prepared by the block copolymerization of methyl methacrylate with P(A-PTHF) as a macroinitiator under ⁶⁰Co γ irradiation. The two-step polymerizations were proved to be controlled with the following evidence: the straight line of ln[M]₀/[M] versus the polymerization time, the linear increase in the number-average molecular weight with the conversion, and the relatively narrow molecular weight distribution. The structures of the P(A-PTHF) and final comb-shaped copolymers were characterized by ¹H NMR spectroscopy and gel permeation chromatography. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3367–3378, 2002

The free-radical polymerization of vinyl monomers in the presence of dibenzyl trithiocarbonate (DBTTC) and under ⁶⁰Co γ-irradiation is of living character. Under ⁶⁰Co irradiation, the bonds between benzyl group and sulfur were cleaved, benzyl radicals initiate the polymerization. The propagating radical together with trithiocarbonate radicals form a dormant polymer chain. The fast equilibrium between propagation radical and dormant polymer chain controls the polymerization.

Cationic ring-opening polymerization of 3,3-dimethyloxetane using C(CH₂OCH₂CH₂CO⁺ClO₄^–)₄ as initiator was examined. The results from ¹H NMR, FTIR and GPC measurements show that a star-shaped poly(3,3-dimethyloxetane) was obtained, and cyclo-oligomers were negligible. The polymerization process was followed by ¹H NMR. Polymerization kinetics were investigated, and the mechanism of the polymerization was discussed.

Triblock copolymers were prepared under ⁶⁰Co γ-irradiation in the presence of a trithiocarbonate macroinitiator. The triblock copolymers, PSt-PMA-PSt and PMA-PSt-PMA have well-defined structures, controlled molecular weight and narrow molecular weight distribution. The mechanism of block copolymerization is discussed.

The controlled free radical polymerization of (2,2-dimethyl-1,3-dioxolan-4-yl)methyl acrylate (DMDMA) was achieved by atom transfer radical polymerization (ATRP) in tetrahydrofuran (THF, 50%, v/v) solution at 90°C with the discotic six-functional initiator, 2,3,6,7,10,11-hexakis(2-bromobutyryloxy) triphenylene (HBTP). The 6-armed polyDMDMA with low polydispersity index (M̄_w/M̄_n = 1.52–1.32) was obtained. The copolymerization of DMDMA with styrene (St) using 6-armed polySt-Br as macroinitiator was carried out, and the GPC traces of the copolymers obtained were unimodal and symmetrical, indicating complete conversion of the macroinitiator into block copolymer. The star-shaped block copolymers with different segment compositions and narrower polydispersity (1.21–1.24) were synthesized, and subsequent hydrolysis of the acetal-protecting group in 1 N HCl THF solution produced poly[St-b-(2,3-dihydroxypropyl)acrylate] [poly(St-b-DHPA)], which was verified by IR and NMR spectroscopy.

A new tetrafunctional initiator, di(hydroxyethyl)-2,9-dibromosebacate (DHEDBS) [HOCH₂CH₂OOCCHBr(CH₂)₆CHBrCOOCH₂CH₂OH], was synthesized and used in preparation of A₂B₂ miktoarm star copolymers, (polystyrene)₂/ [poly(1,3-dioxepane)]₂ [S-(PSt)₂(PDOP)₂], by transformation of atom transfer radical polymerization (ATRP) to cationic ring-opening polymerization (CROP). First, two-armed PSt with two primary hydroxyl groups sited at the center of macromolecule [(PStBr)₂(OH)₂] was obtained by ATRP of St with the initiation system of DHEDBS/CuBr/bpy, and used as a chain-transfer agent in the CROP of DOP with triflic acid as the initiator. Therefore, A₂B₂ miktoarm star copolymer S-(PSt)₂(PDOP)₂ was formed. Its structure was confirmed by the ¹H NMR spectrum. Gel permeation chromatography (GPC) curves show that the polymers obtained have a relatively narrow molecular weight distribution. The hydrolysis product of S-(PSt)₂(PDOP)₂ was also characterized by ¹H NMR and GPC. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 437–445, 2001

A novel hexafunctional discotic initiator, 2,3,6,7,11,12-hexakis(2-bromobutyryloxy)triphenylene (HBTP), was synthesized by the esterification of 2,3,6,7,11,12-hexahydroxytriphenylene with 2-bromobutyryl chloride. Atom transfer radical polymerizations of styrene, methyl acrylate, and n-butyl acrylate were carried out in 50 vol % tetrahydrofuran with HBTP/copper(I) bromide/2,2′-bipyridyl as an initiation system. The polymers produced had well-controlled molecular weights and narrow molecular weight distributions (<1.2). On the basis of ¹H NMR spectra of the star polymer and its hydrolyzed products, we can conclude that the initiator quantitatively initiated the polymerization of vinyl monomers and that a star polymer with a discotic core was obtained. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2233–2243, 2001

The synthesis of A₄B₄ miktoarm star copolymers, where A is polytetrahydrofuran (PTHF) and B is polystyrene (PSt), was accomplished with orthogonal initiators and consecutive cationic ring-opening polymerization (CROP) and atom transfer radical polymerization (ATRP). The compound formed in situ from the reaction of 3-{2,2-bis[2-bromo-2-(chlorocarbonyl) ethoxy] methyl-3-(2-chlorocarbonyl) ethoxy} propoxyl-2-bromopropanoyl chloride [C(CH₂OCH₂CHBrCOCl)₄] with silver perchlorate was used to initiate the CROP of tetrahydrofuran. The obtained polymer contained four secondary bromine groups at the α position to the original initiator sites and was used to initiate the ATRP of styrene with a CuBr/2,2′-bipyridine catalyst to form a C(PTHF)₄(PSt)₄ miktoarm star copolymer. The miktoarm copolymer was characterized by gel permeation chromatography and ¹H NMR. The macroinitiator C(PTHF)₄Br₄ was hydrolyzed to afford PTHF arms. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2134–2142, 2001

The polymers poly[(2,2-dimethyl-1,3-dioxolane-4yl) methyl acrylate] (PDMDMA) and four-armed PDMDMA with well-defined structures were prepared by the polymerization of (2,2-dimethyl-1,3-dioxolane-4yl) methyl acrylate (DMDMA) in the presence of an atom transfer radical polymerization (ATRP) initiator system. The successive hydrolyses of the polymers obtained produced the corresponding water-soluble polymers poly(2,3-dihydroxypropyl acrylate) (PDHPA) and four-armed PDHPA. The controllable features for the ATRP of DMDMA were studied with kinetic measurements, gel permeation chromatography (GPC), and NMR data. With the macroinitiators PDMDMA–Br and four-armed PDMDMA–Br in combination with CuBr and 2,2′-bipyridine, the block polymerizations of methyl acrylate (MA) with PDMDMA were carried out to afford the AB diblock copolymer PDMDMA-b-MA and the four-armed block copolymer S{poly[(2,2-dimethyl-1,3-dioxolane-4yl) methyl acrylate]-block-poly(methyl acrylate)}₄, respectively. The block copolymers were hydrolyzed in an acidic aqueous solution, and the amphiphilic diblock and four-armed block copolymers poly(2,3-dihydroxypropyl acrylate)-block-poly(methyl acrylate) were prepared successfully. The structures of these block copolymers were verified with NMR and GPC measurements. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3062–3072, 2001

The polymerization of acrylic acid (AA) was performed under ⁶⁰Co irradiation in the presence of dibenzyl trithiocarbonate at room temperature, and well-defined poly(acrylic acid) (PAA) with a low polydispersity index was successfully prepared. The gel permeation chromatographic and ¹H NMR data showed that this polymerization displays living free-radical polymerization characteristics: a narrow molecular weight distribution (M_w/M_n = 1.07–1.22), controlled molecular weight, and constant chain-radical concentration during the polymerization. Using PAAS C(S)SPAA as an initiator, the extension reaction of PAA with fresh AA was carried out under ⁶⁰Co irradiation, and the results indicated that this extension polymerization displayed controlled polymerization behavior. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3934–3939, 2001

Polymerizations of methylacrylate, styrene and methyl methacrylate were carried out in the presence dithiobenzoic acid (DTBA). The results exhibit controlled polymerization characters: well-controlled molecular weight, narrow molecular weight distribution (minimal value: 1.08), molecular weight linearly increasing with conversion and first-order kinetics of polymerization. The polymers were characterized by ¹H NMR and GPC. The effect of temperature and molar ratio DTBA/AIBN on polymerization was investigated. A mechanism is proposed to explain the controlled polymerization characters.

© 2000 Society of Chemical Industry

The “living” free radical ring-opening polymerization of 2-methylene-4-phenyl-1,3-dioxolane (MPDO) in the presence of ethyl α-bromobutyrate/CuBr/2,2′-bipyridine at various temperatures has been investigated. In comparison with the conventional ring-opening polymerization of MPDO, a lower content of ring-opened unit in the polymer was found. The results of ln[M]₀/[M]) against polymerization time, (M_n)_th and (M_n)_NMR vs conversion, and GPC of the polymers are strongly indicative of the “living” polymerization process. Initiator efficiency was measured. The mechanism of polymerization, and the effect of pyridine on the polymerization mechanism were discussed.