Block copolymers styrene-HEMA

Reprined from J. Biomed. Mater. Research [Ref. 82 Blood compatibility of PEO grafted polyurethane and HEMA/styrene block copolymer surfaces] through the courtesy of John Wiley Sons. Inc.)... 

Di-block copolymers may also be formed by using dithiocarbamate free radicals. Indeed, copoljoners containing poly(styrene) and poly(hydroxyethyl methacrylate) blocks have been obtained by a two-step procedure [145]. Firstly, styrene is photopolymerized in the presence of benzyl A,A-diethyldithiocarbamate (BDC) by a living radical mechanism [146]. In fact, as the benzyl and thiyl radicals, formed by the photoliagmentation of BDC, participate mainly in the initiation and termination reactions respectively, polystyrene with a dithiocarbamate end group is thus obtained. The successive UV irradiation of this polymer, in the presence of hydroxyethyl methacrylate (HEMA), gives rise to the di-block copolymer, according to Scheme 42. 

Block copolymers with hydroxyl segments were prepared by various ways An example utilizes the copper-catalyzed sequential copolymerizations of nBA and 2-[(trimethylsilyl)oxy]ethyl acrylate by the macroinitiator method into B-31 to B-33. The copolymers were then hydrolyzed into amphiphilic forms by deprotection of the silyl groups.313 A direct chain-extension reaction of polystyrene and PMMA with HEMA also afforded similar block copolymers with hydroxyl segments (B-34 and B-35).241-243 In block polymer B-36, a hydroxy-functionalized acrylamide provides a hydrophilic segment.117 Block copolymers of styrene and p-acetoxystyrene (B-37 to B-39), prepared by iron... 

TMPAH was used successfully for the homo-, co-, and block polymerizations of IP. In this case, due to the less reactive diene monomer, no additional free nitroxide was necessary to control the polymerization and both low and high molecular weight polymers (Mn=4500 to Mn=100,000) with narrow molecular weight distributions (Mw/Mn= 1.07-1.3) were synthesized [159]. Copolymers with various styrene and (meth)acrylate derivatives, including acrylic acid and HEMA, were obtained, with the content of isoprene varying from 10% to 90% in the comonomer feed. Block copolymers were also produced, starting from either ptBA or pSt macroinitiators however, the alternate order of blocks (i.e., starting from a pIP macroinitiator) was only achieved with St. Chain extension with tBA resulted in inefficient initiation [159], as had been found for pSt-pnBA block copolymers [71]. 

Nojiri C, Gkano T, Jacobs HA, Park KD, Mohammad SF, Glsen DB, et al. Blood compatibility of PEG grafted polyurethane and HEMA/styrene block copolymer surfaces. J Biomed Mater Res 1990 24(9) 1151-71. 

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