Analysis of an order-order transition of a triblock copolymer (BCP), sulfonated BCP (SBCP), and SBCP/silicate hybrid by dynamic mechanical analyses

摘要

Microphase separation in block copolymers (BCPs) having two immiscible blocks A and B is primarily determined by the product x_(AB)N, where x_(AB) is the Flory-Huggins interaction parameter and N is the number average degree of polymerization. As this product increases, micro-phase separation becomes more complete and interphases become less diffuse. Due to the inverse relationship between x_(AB) and temperature, BCPs exhibit a phenomenon similar to an upper critical solution temperature (UCST) in polymer blends. Above a critical temperature, x_(AB)N is lowered enough to allow for statistical mixing of the Z and B blocks and the system is transformed from an ordered, phase-separated microstructure to a disordered, A-B mixed microstructure displaying near-Newtonian flow behavior. This is referred to as the order-disorder transition (ODT) or microphase separation transition (MST). The ODT allows for melt processing BCPs because of the sharp reduction in viscosity above the ODT temperature.