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) sequential anionic synthesis of the isotactic polystyrene followed by the polybutadiene block and (b) end functionalization and coupling of the two homopolymers. The polybutadiene blocks were prepared by anionic polymerization, with a resulting microstructure of approximately 90% 1,4 and 10% 1,2 addition. The preparation of the isotactic polystyrene block involved a novel anionic polymerization technique using a nonpolar solvent, low temperatures, and the addition of tert-BuOLi to induce stereospecific placement.1 The polymers were fully characterized by GPC, H-1 and C-13 NMR, and DSC to determine molecular weights, tacticity, and thermal transitions. Wide-angle X-ray scattering was used to determine the crystallinity of the iPS regions of the heterogeneous materials. The blocklike structure of the copolymers was supported by the results of transmission electron microscopy (TEM), which revealed morphological order and length scales typical of microphase-separated block copolymers.