Sequence Effects on the Glass Transition Temperature of Silicone-Containing Copolymers

Abstract

Copolymerization, producing varying copolymer sequences, is a practical method to control the glass transition temperature, which can broaden the temperature range of their use and adapt to different scenarios. However, the connection of copolymer sequences with glass transition temperatures is still unclear. In this work, we employed an all-atom molecular dynamics simulation to explore the sequence effect on the glass transition temperature of silicone-containing copolymers. The results indicated that the Flory–Fox equation and linear relation effectively describe the correlation between glass transition temperatures and compositions of poly(methylphenyl-co-methylvinyl) siloxane with alternating block sequences, while diblock sequences exhibit positive deviations. In comparison, the glass transition temperatures of poly(methylphenyl-co-dimethyl) siloxane with all sequences deviate positively from the Flory–Fox equation and linear relation. The analysis revealed that the self-concentration effect plays a dominant role in the positive deviations, which is closely associated with the rigidity of the monomers constituting the copolymers. The result provides a fundamental understanding of the sequence effect on the glass transition temperature of copolymers and could guide the rational design of silicone-containing copolymers with controlled glass transition temperatures.