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Complex Macromolecular Architectures (complex + macromolecular_architecture)
Selected AbstractsTitanium-mediated [CpTiCl2(OEt)] ring-opening polymerization of lactides: A novel route to well-defined polylactide-based complex macromolecular architecturesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2010Nikolaos Petzetakis Abstract Among three cyclopentadienyl titanium complexes studied, CpTiCl2(OEt), containing a 5% excess CpTiCl3, has proven to be a very efficient catalyst for the ring-opening polymerization (ROP) of L -lactide (LLA) in toluene at 130 °C. Kinetic studies revealed that the polymerization yield (up to 100%) and the molecular weight increase linearly with time, leading to well-defined PLLA with narrow molecular weight distributions (Mw/Mn , 1.1). Based on the above results, PS- b -PLLA, PI- b -PLLA, PEO- b -PLLA block copolymers, and a PS- b -PI- b -PLLA triblock terpolymer were synthesized. The synthetic strategy involved: (a) the preparation of OH-end-functionalized homopolymers or diblock copolymers by anionic polymerization, (b) the reaction of the OH-functionalized polymers with CpTiCl3 to give the corresponding Ti-macrocatalyst, and (c) the ROP of LLA to afford the final block copolymers. PMMA- g -PLLA [PMMA: poly(methyl methacrylate)] was also synthesized by: (a) the reaction of CpTiCl3 with 2-hydroxy ethyl methacrylate, HEMA, to give the Ti-HEMA-catalyst, (b) the ROP of LLA to afford a PLLA methacrylic-macromonomer, and (c) the copolymerization (conventional and ATRP) of the macromonomer with MMA to afford the final graft copolymer. Intermediate and final products were characterized by NMR spectroscopy and size exclusion chromatography, equipped with refractive index and two-angle laser light scattering detectors. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1092,1103, 2010 [source] Well-defined complex macromolecular architectures by anionic polymerization of styrenic single and double homo/miktoarm star-tailed macromonomersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2008Paraskevi Driva Abstract 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 [source] Recent advances in the synthesis of well-defined glycopolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2007Sebastian G. Spain Abstract Glycopolymers are receiving increasing interest due to their application in areas, such as glycomics, medicine, biotechnology, sensors, and separation science. Consequently, new methods for their synthesis are constantly being developed, with an increasing emphasis on the preparation of well-defined polymers and on the production of complex macromolecular architectures such as stars. This review covers recent developments in the synthesis of glycopolymers, with a particular emphasis on (i) the use of controlled radical polymerization to prepare well-defined glycopolymers from unprotected monomers and (ii) postpolymerization modification strategies using reactive polymer precursors (including "click" reactions). Recent work on the production of glycosylated polypeptides, which are under investigation as mimics of naturally occurring glycoproteins, is also included. The authors offer some suggestions as to future developments and remaining challenges in this topical area of polymer chemistry. © 2007 Wiley Periodicals, Inc. J Polym Sci PartA: Polym Chem45: 2059,2072, 2007 [source] Nitroxide-mediated radical polymerization of N -ethyl-2-vinylcarbazolePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 6 2008Jeffrey D. Quinn Abstract The hole-transporting ability of carbazole-containing polymers makes them attractive for applications in organic electronics. Nitroxide-mediated radical polymerization (NMRP) offers the potential to create complex macromolecular architectures, including block copolymers, but N -vinylcarbazole, the simplest and most widely studied carbazole monomer, is known to polymerize poorly by NMRP. Here, we investigate the NMRP of N -ethyl-2-vinylcarbazole (2,VK), a monomer structurally more similar to the styrenes which are known to polymerize well by NMRP, and whose polymer offers a hole mobility an order of magnitude higher than poly(N -vinylcarbazole). Polymerization of 2,VK from a unimolecular alkoxyamine shows a molecular weight which increases steadily with time, though termination or decomposition of the "living" radical ends is clearly evident from the progressive formation of a low-molecular-weight tail as conversion increases. However, a sufficient fraction of the chains remain living that P2VK-PS diblock copolymer can be formed by chain extension of the P2VK macroinitiator with styrene. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||