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Star-block Copolymers (star-block + copolymer)
Selected AbstractsOne-pot synthesis of star-block copolymers using double click reactionsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2008Hakan Durmaz Abstract 3-Arm star-block copolymers, (polystyrene- b -poly(methyl methacrylate))3, (PS- b -PMMA)3, and (polystyrene- b -poly(ethylene glycol))3, (PS- b -PEG)3, are prepared using double-click reactions: Huisgen and Diels,Alder, with a one-pot technique. PS and PMMA blocks with ,-anthracene-,-azide- and ,-maleimide-end-groups, respectively, are achieved using suitable initiators in ATRP of styrene and MMA, respectively. However, PEG obtained from a commercial source is reacted with 3-acetyl- N -(2-hydroxyethyl)-7-oxabicyclo[2.2.1]hept-5-ene-2-carboxamide (7) to give furan-protected maleimide-end-functionalized PEG. Finally, PS/PMMA and PS/PEG blocks are linked efficiently with trialkyne functional linking agent 1,1,1-tris[4-(2-propynyloxy)phenyl]-ethane 2 in the presence of CuBr/N,N,N,,N,,N, -pentamethyldiethylenetriamine (PMDETA) at 120 °C for 48 h to give two samples of 3-arm star-block copolymers. The results of the peak splitting using a Gaussian deconvolution of the obtained GPC traces for (PS- b -PMMA)3 and (PS- b -PEG)3 displayed that the yields of target 3-arm star-block copolymers were found to be 88 and 82%, respectively. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7091,7100, 2008 [source] Amphiphilic star-block copolymers based on a hyperbranched core: Synthesis and supramolecular self-assemblyJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2005Zhifeng Jia Abstract Novel amphiphilic star-block copolymers, star poly(caprolactone)- block -poly[(2-dimethylamino)ethyl methacrylate] and poly(caprolactone)- block -poly(methacrylic acid), with hyperbranched poly(2-hydroxyethyl methacrylate) (PHEMA,OH) as a core moiety were synthesized and characterized. The star-block copolymers were prepared by a combination of ring-opening polymerization and atom transfer radical polymerization (ATRP). First, hyperbranched PHEMA,OH with 18 hydroxyl end groups on average was used as an initiator for the ring-opening polymerization of ,-caprolactone to produce PHEMA,PCL star homopolymers [PHEMA = poly(2-hydroxyethyl methacrylate); PCL = poly(caprolactone)]. Next, the hydroxyl end groups of PHEMA,PCL were converted to 2-bromoesters, and this gave rise to macroinitiator PHEMA,PCL,Br for ATRP. Then, 2-dimethylaminoethyl methacrylate or tert -butyl methacrylate was polymerized from the macroinitiators, and this afforded the star-block copolymers PHEMA,PCL,PDMA [PDMA = poly(2-dimethylaminoethyl methacrylate)] and PHEMA,PCL,PtBMA [PtBMA = poly(tert -butyl methacrylate)]. Characterization by gel permeation chromatography and nuclear magnetic resonance confirmed the expected molecular structure. The hydrolysis of tert -butyl ester groups of the poly(tert -butyl methacrylate) blocks gave the star-block copolymer PHEMA,PCL,PMAA [PMAA = poly(methacrylic acid)]. These amphiphilic star-block copolymers could self-assemble into spherical micelles, as characterized by dynamic light scattering and transmission electron microscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6534,6544, 2005 [source] Carbocationic Polymerizations for Profit and FunMACROMOLECULAR SYMPOSIA, Issue 1 2004Ralf M. Peetz Abstract This presentation consists of two largely independent parts: The first åfor Profit, part concerns a bird's eye view of recently commercialized carbocationic processes and materials created by these processes in the author's laboratories whose marketing started during the past ,5 years by various companies. These materials/processes include liquid telechelic polyisobutylene (PIB) for architectural sealants, poly(styrene- b -isobutylene- b -styrene) (PSt- b -PIB- b -PSt) triblocks for thermoplastic elastomers, PIB/PSt-based blocks for coating of medical devices, and PIB-based microemulsions for surface protection of painted metal surfaces. It is concluded that in order to enhance and solidify research in polymer synthesis it would behoove the scientific community to pay increased attention to intellectual property protection. Appropriately managed patenting and publishing activities are self-reinforcing and may be quite profitable. The second "for Fun" part concerns a brief review of the design, synthesis and characterization of two novel fully aliphatic star-block copolymers: ,(PIB- b -PNBD)3 and ,(PNBD- b -PIB)3 (where PNBD = polynorbornadiene). The constituent moieties of these star-blocks are identical except their block sequences are reversed. Motivation for the synthesis of ,(PIB- b -PNBD)3, consisting of a low Tg (,-73°C) PIB inner-corona attached to a high Tg (,320°C) PNBD outer corona, was the expectation that this star-block would exhibit thermoplastic elastomer characteristics, and that it could be used in applications where similar polyaromatic-based TPEs cannot be employed (e.g., magnetic signal storage). The other star-block, ,(PNBD- b -PIB)3, comprises the same building blocks with the PIB and PNBD sequences reversed. We found that the secondary chlorine at the PNBD chain end, in conjunction with TiCl4, is able to initiate the polymerization of isobutylene. Details of the carbocationic polymerization of NBD, together with the microstructure of PNBD, will be discussed. [source] | ||||||||||