Synthesis of SAN-PB-SAN triblock copolymers via a ''living'' copolymerization with macro-photoiniferters

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