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Hydroxyl End Groups (hydroxyl + end_groups)
Selected AbstractsSynthesis and self-assembly of well-defined cyclodextrin-centered amphiphilic A14B7 multimiktoarm star copolymers based on poly(,-caprolactone) and poly(acrylic acid)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2010Peng-Fei Gou Abstract Novel amphiphilic A14B7 multimiktoarm star copolymers composed of 14 poly(,-caprolactone) (PCL) arms and 7 poly(acrylic acid) (PAA) arms with ,-cyclodextrin (,-CD) as core moiety were synthesized by the combination of controlled ring-opening polymerization (CROP) and atom transfer radical polymerization (ATRP). 14-Arm star PCL homopolymers (CDSi-SPCL) were first synthesized by the CROP of CL using per-6-(tert -butyldimethylsilyl)-,-CD as the multifunctional initiator in the presence of Sn(Oct)2 at 125 °C. Subsequently, the hydroxyl end groups of CDSi-SPCL were blocked by acetyl chloride. After desilylation of the tert -butyldimethylsilyl ether groups from the ,-CD core, 7 ATRP initiating sites were introduced by treating with 2-bromoisobutyryl bromide, which further initiated ATRP of tert -butyl acrylate (tBA) to prepare well-defined A14B7 multimiktoarm star copolymers [CDS(PCL-PtBA)]. Their molecular structures and physical properties were in detail characterized by 1H NMR, SEC-MALLS, and DSC. The selective hydrolysis of tert -butyl ester groups of the PtBA block gave the amphiphilic A14B7 multimiktoarm star copolymers [CDS(PCL-PAA)]. These amphiphilic copolymers could self-assemble into multimorphological aggregates in aqueous solution, which were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM) and atomic force microscopy (AFM). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2961,2974, 2010 [source] Mechanistic investigations of antimony-catalyzed polycondensation in the synthesis of poly(ethylene terephthalate)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2006Faissal-Ali El-Toufaili Abstract The chemical aspects of poly(ethylene terephthalate) synthesis via the antimony-catalyzed polycondensation of hydroxy ethylene terephthalate end groups were studied to elucidate its mechanism. A polycondensation mechanism was proposed in which activation occurs by the formation of a chelate ligand on antimony composed of the hydroxyl end group and alcoholic oxygen of the ester of the same end group. The rate-determining step of the polycondensation reaction was concluded to be the coordination of a second chain end to antimony. The low activity of antimony at a high concentration of hydroxyl end groups was proposed to result from the competition between hydroxyl end groups and the chelate structure leading to the transition state. The high selectivity of antimony is probably due to its relatively low Lewis acidity. Moreover, antimony was found to stabilize hydroxyl end groups against degradation by preventing their complexation to carbonyl functionalities. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1049-1059, 2006 [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] Poly(butylene terephthalate)/poly(,-caprolactone) blends: Miscibility and thermal and mechanical propertiesPOLYMER ENGINEERING & SCIENCE, Issue 3 2007Maria Laura Di Lorenzo Miscibility and thermal and mechanical properties of poly(butylene terephthalate) (PBT) blends with poly(,-caprolactone) (PCL) were analyzed as a function of the molecular mass of PCL. It was found that the components are miscible when oligomeric PCL is blended with PBT, probably due to favorable interactions between OH end groups of poly(,-caprolactone) and ester groups of PBT. In the blends containing high molar mass PCL, the concentration of hydroxyl end groups is lower, allowing only partial miscibility of the components. The resulting materials display good mechanical properties, with enhanced performance at rupture compared to plain PBT. POLYM. ENG. SCI., 47:323,329, 2007. © 2007 Society of Plastics Engineers. [source] | ||||||||||