NOVEL STYRENE-BUTADIENE BLOCK POLYMERS BY SEQUENTIAL AND STATISTICAL COPOLYMERIZATION OF CORRESPONDING MACROMONOMERS

This paper concerns the synthesis of two different structures of styre ne-butadiene block copolymers that were respectively obtained via sequ ential and statistical ring-opening metathesis copolymerization of nor bornene-terminated polystyrene (PS) and polybutadiene (PB) macromonome rs. The stimulus for preparing such styrene-butadiene copolymers origi nates from the observation that phase-separated morphologies in block copolymers not only depend on the respective size of the blocks and th e interaction parameter (chi), but also on the topological constraints introduced in the copolymer structure. From the differential scanning calorimetry study that was carried, it can be inferred that the two t ypes of copolymers-prepared by sequential and statistical copolymeriza tion of PS and PB macromonomers respectively-exhibit quite different p hase separation behaviors, indicating that they develop distinct equil ibrium domain morphologies.