SYNTHESIS OF SAN-PB-SAN TRIBLOCK COPOLYMERS VIA A LIVING COPOLYMERIZATION WITH MACRO-PHOTOINIFERTERS

A technique is described for the synthesis of -block-butadiene-block-( styrene-co-acrylonitrile)) (SAN-PB-SAN) triblock copolymers through po lybutadiene-based photo-iniferters. Dihydroxy- and dicarboxy-terminate d polybutadienes were transformed into the chloro-terminated compounds , which were subsequently reacted with sodium diethyldithiocarbamate i nto macro-photoiniferters. The dicarboxy-terminated polybutadiene was found to produce unstable dithiocarbamate end groups because of loss o f CS2. The dihydroxy-terminated polybutadiene (M(n) = 3300 g/mol) was successfully transformed into a macro-photoiniferter, which was used a s a photoinitiator for the ''living'' copolymerization of styrene/acry lonitrile mixtures to obtain the title compounds. By variation of the polymerization time and macroiniferter concentration, the vinyl sequen ce length and composition of the triblock copolymers could be regulate d. The macroiniferters and block copolymers were characterized by GPC, elemental analysis, and H-1 MMR.