title: Synthesis of multiarm star poly(glycerol)-block-poly(2-hydroxyethyl methacrylate).
abstract: Well-defined multiarm star block copolymers poly(glycerol)-b-poly(2-hydroxyethyl methacrylate) (PG-b-PHEMA) with an average of 56, 66, and 90 PHEMA arms, respectively, have been prepared by atom transfer radical polymerization (ATRP) of HEMA in methanol by a core-first strategy. The hyperbranched macroinitiators employed were prepared on the basis of well-defined hyperbranched polyglycerol by esterification with 2-bromoisobutyryl bromide. Polydispersites M(w)/M(n) of the new multiarm stars were in the range of 1.11-1.82. Unexpectedly, with the combination of CuCl/CuBr(2)/2,2'-bipyridyl as catalyst, the polymerization conversion can be driven to maximum values of 79%. The control of CuCl catalyst concentration is also very important to achieve high conversion and narrow polydispersity. The absolute M(n) values of the obtained multiarm star polymers were in good agreement with the calculated ones, and the highest M(n) values of the multiarm star copolymer is around 10(6) g/mol. Kinetic analysis shows that an induction period exists in the polymerization of HEMA. After this induction period, a linear dependence of ln ([M](0)/[M](t)()) on time was observed. Due to the star architecture, the viscosity of the obtained multiarm star PHEMA is much lower than that of linear PHEMA.
authors.affiliation: Department of Chemistry, Tianjin University, 300072, Tianjin, People's Republic of China. chenyu@tju.edu.cn
authors.forename: Yu
authors.initials: Y
authors.lastname: Chen
authors.forename: Zhong
authors.initials: Z
authors.lastname: Shen
authors.forename: Emilie
authors.initials: E
authors.lastname: Barriau
authors.forename: Holger
authors.initials: H
authors.lastname: Kautz
authors.forename: Holger
authors.initials: H
authors.lastname: Frey
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D002384:Catalysis; D007700:Kinetics; D046911:Macromolecular Substances / Q000737:chemistry; D008689:Methacrylates / Q000138:chemical synthesis* / Q000737:chemistry*; D008956:Models, Chemical; D015394:Molecular Structure; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry
chemical_list: D001672:Biocompatible Materials; D046911:Macromolecular Substances; D008689:Methacrylates; D011108:Polymers; D011092:Polyethylene Glycols; C005044:hydroxyethyl methacrylate