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131.
Paraskevi Driva David J. Lohse Nikos Hadjichristidis 《Journal of polymer science. Part A, Polymer chemistry》2008,46(5):1826-1842
Styrenic single and double star‐tailed macromonomers were synthesized by selective reaction of living homo/miktoarm stars with the chlorosilane groups of 4‐(chlorodimethylsilyl)‐ and 4‐(dichloromethylsilyl)styrene, respectively. The in situ anionic homopolymerization of macromonomers with sec‐BuLi and copolymerization with butadiene and styrene, led to single/double homo/miktoarm star‐tailed molecular brushes and combs, as well as a block copolymer consisting of a linear polystyrene chain and a double miktoarm (PBd/PS) star‐tailed brush‐like block. Molecular characterization by size exclusion chromatography, size exclusion chromatography/two‐angle laser light scattering, and NMR spectroscopy, revealed the high molecular/compositional homogeneity of all intermediate and final products. These are only a few examples of the plethora of complex architectures possible using the above macromonomers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1826–1842, 2008 相似文献
132.
N-Propargylamide-terminated peptide-based macromonomers with a degree of polymerization ranging from 4 to 40 were synthesized by the polymerization of gamma-benzyl and gamma-stearyl-L-glutamate-N-carboxy anhydrides initiated with propargylamine. The macromonomers took an alpha-helical structure, which was confirmed by signals at 208 and 220 nm in CD spectra. The macromonomers were subjected to polymerization and copolymerization with an alanine-derived N-propargylamide [N-(tert-butoxycarbonyl)-L-alanine-N'-propargylamide] catalyzed with (2,5-norbornadiene)Rh+[eta6-C6H5B- (C6H5)3]. It was confirmed through a CD spectroscopic study that the copolymer obtained from the copolymerization of the gamma-stearyl-L-glutamate-based macromonomer with the alanine-derived N-propargylamide had a helical polyacetylene main chain and helical polypeptide side chains. 相似文献
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134.
Bindushree Radhakrishnan Goretti Balerdi Eric Cloutet Henri Cramail 《Macromolecular Symposia》2005,229(1):56-65
Summary: The synthesis of polyurethane particles by polyaddition of ethylene glycol (EG) and tolylene-2,4-diisocyanate (TDI) in cyclohexane at 60 °C was investigated in the presence of ω-hydroxy and ω,ω′-dihydroxy polybutadiene, used as reactive steric stabilizers. The effect of the functionality and concentration of the reactive polybutadiene, as well as the monomer addition procedure, onto the polyurethane particle formation was studied. Calibrated PUR particles with an average diameter in the range 1–2 µm could be readily obtained. 相似文献
135.
Ikuo Taniguchi William A. Kuhlman Linda G. Griffith Anne M. Mayes 《Macromolecular rapid communications》2006,27(8):631-636
Summary: Commercial hydroxy‐terminated poly(ethylene glycol) monomethacrylates (PEG‐MAs) contain poly(ethylene glycol) dimethacrylate, which leads to unfavorable gel formation on polymerization. Here, hydroxy‐terminated PEG‐MA is readily isolated using a dimethylsilyl resin chlorinated with 1,3‐dichloro‐5,5‐dimethylhydantoin. Solution polymerization of the isolated PEG‐MA by free radical routes gives a high‐molecular‐weight amphiphilic graft copolymer without cross‐linking. The resulting polymer is stable for long periods in ambient conditions with preservation of the hydroxy end groups of PEG.
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138.
Hideyuki Kaneko Shin-ichi Kojoh Nobuo Kawahara Shingo Matsuo Tomoaki Matsugi Norio Kashiwa 《Macromolecular Symposia》2004,213(1):335-346
Polymacromonomers with polyolefin branches were successfully synthesized by free-radical homopolymerization of polyolefin macromonomer with a methacryloyl end group. Propylene-ethylene random copolymer (PER) with a vinylidene end group was prepared by polymerization using a metallocene catalyst. Then, the unsaturated end group was converted to a hydroxy end group via hydroalumination and oxidation. The PER with the hydroxy end group was easily reacted with methacryloyl chloride to produce methacryloyl-terminated PER (PER macromonomer; PERM). The free-radical polymerization of thus-obtained PERM was done using 2,2′-azobis(isobutyronitorile) (AIBN) as a free-radical initiator. From NMR analyses, the obtained polymers were identified as poly(PERM). Based on gel permeation chromatography (GPC), the estimated degree of polymerization (Dp) of these polymers were about 30. Thus, new class of polymacromonomers with polyolefin branches was synthesized. 相似文献
139.
Rate constants for long‐chain branch formation during ethylene polymerization with metallocene catalysts were estimated and compared to polymerization rate constants for long α‐olefins. Unexpectedly, these branching constants were found to be comparable to the reactivity ratios of much shorter α‐olefins. Micromixing effects or a parallel mechanism for long‐chain branch generation are proposed as possible explanations for this finding.
140.
Weiqing Weng Eric J. Markel Armenag H. Dekmezian 《Macromolecular rapid communications》2001,22(18):1488-1492
Long‐chain branched (LCB) poly(propylene)s (PP) are synthesized by the incorporation of pre‐formed, vinyl‐terminated macromonomers using metallocene catalysts. LCB‐PP polymers made with isotactic PP macromonomers are characterized by means of multi‐angle laser light scattering and extensional viscosimetry. The LCB polymers exhibit enhanced melt properties, such as strain hardening and shear thinning. These properties are critical in many polymer fabrication processes, such as thermoforming, blow molding and foaming. 相似文献