Precise synthesis of thermo-responsive and water-soluble star-branched polymers and star block copolymers by living anionic polymerization |
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Authors: | Akira Hirao Reiko Inushima Takefumi Nakayama Takumi Watanabe Hee-Soo Yoo Takashi Ishizone Kenji Sugiyama Toyoji Kakuchi Stephane Carlotti Alain Deffieux |
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Affiliation: | aPolymeric and Organic Materials Department, Graduate School of Science and Engineering, Tokyo Institute of Technology, H-127, 2-12-1, Ohokayama, Meguro-ku, Tokyo 152-8552, Japan;bDivision of Biotechnology and Macromolecular Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan;cCNRS, Université Bordeaux1, Laboratoire de Chimie des Polymères Organiques, UMR5629, 16, Avernue Pey Berland, 33607 Pessac Cedex, France |
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Abstract: | A series of thermo-responsive and water-soluble 4- and 8-arm star-branched poly(2-(2′-methoxyethoxy)ethyl methacrylate) (poly(1)) with well-defined structures were synthesized by living anionic polymerization of 1, followed by a linking reaction with a core compound substituted with either four or eight benzyl bromide moieties. Furthermore, two kinds of sequentially different 4-arm star block copolymers composed of poly(1)-block-poly ((2,2-dimethyl-1,3-dioxolan-4-yl)methyl methacrylate) (poly(4)) were also synthesized by the same linking reaction of the corresponding AB or BA diblock copolymer anion with a core compound substituted with four benzyl bromide moieties. Thus, both well-defined 4-arm (AB)4 and (BA)4 star-block copolymers, whose A and B are poly(1) and poly(4) segments, were successfully synthesized. These star-block copolymers were quantitatively converted to the corresponding 4-arm (AC)4 and (CA)4 star-block copolymers with the same compositions by hydrolytic acetal cleavage of the poly(4) segment to poly(2,3-dihydroxypropyl methacrylate) (C segment). Poly(1) segments have LCST values and, on the other hand, both water-insoluble poly(4)s and water-soluble poly(2,3-dihydroxypropyl methacrylate)s are non-thermo-responsive segments. The thermo-responsive behavior of the resulting 4- and 8-arm star-branched poly(1) as well as the 4-arm (AB)4, (BA)4, (AC)4, and (CA)4 star-branched block copolymers has been extensively studied in terms of molecular weight, arm number, composition, and block sequence. As expected, such variables were observed to affect their LCST values. Interestingly, the thermo-responsive behavior of the 4-arm (AC)4 and (CA)4 stars was different from that of the block copolymers used as arm segments. |
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Keywords: | Thermo-responsive polymer Water-soluble polymer Star-branched polymer Star block copolymers Poly(2-(2&prime -methoxyethoxy)ethyl methacrylate) Living anionic polymerization |
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