NOVEL STYRENE-BUTADIENE BLOCK COPOLYMERS BY SEQUENTIAL AND STATISTICAL COPOLYMERIZATION OF CORRESPONDING MACROMONOMERS
Abstract
This paper concerns the synthesis of two different structures of styrene-butadiene block copolymers that were respectively obtained via sequential and statistical ring-opening metathesis copolymerization of norbornene-terminated polystyrene (PS) and polybutadiene (PB) macromonomers. The stimulus for preparing such styrene-butadiene copolymers originates from the observation that phase-separated morphologies in block copolymers not only depend on the respective size of the blocks and the interaction parameter (x), but also on the topological constraints introduced in the copolymer structure. From the differential scanning calorimetly study that was carried, it can be inferred that the two types of copolymers-prepared by sequential and statistical copolymerization of PS and PB macromonomers respectively-exhibit quite different phase separation behaviors, indicating that they develop distinct equilibrium domain morphologies.