Synthesis and Characterization of Isotactic Polystyrene-Polybutadiene Block Copolymers

Diblock copolymers of isotactic polystyrene and 1,4 polybutadiene were successfully synthesized by two methods a coupling of two endfunctionalized homopolymers, and b sequential synthesis of the two blocks. The polybutadiene blocks were prepared by anionic synthesis yielding 90 1,4 cis-trans and 10 1,2 addition. The preparation of the isotactic polystyrene block involved a novel anionic polymerization technique using low temperatures and the addition of BuOLi for stereospecific placement. Overall isotactic yields of 10 by weight were obtained, the remainder being unreacted monomer 50 and atactic material 40. The polymers were characterized by GPC, NMR and DSC to determine molecular weights, tacticity and percent crystallinity. The block-like nature of the copolymer was further analyzed through transmission electron microscopy.