Liquid–Liquid Transition and Detrapping of Trapped Carriers of P(MMA/BA) Copolymers by Thermally Stimulated Depolarization Current

Abstract

Poly (methyl methacrylate/butyl acrylate) [P(MMA/BA)] copolymers (M η∼2×105) with different mass percentages of PMMA (100/0, 90/10, 81/19, and 75/25), were synthesized by the method of solution polymerization. In addition to the normal α and ρ peak, a third τ peak is observed in thermally stimulated depolarization current (TSDC) spectra of the copolymers in the high temperature region. The α peak‐corresponds to the glass transition, the ρ peak originates from the detrapping of trapped carriers in the bulk amorphous structure related with flexible side groups, and the τ peak can be attributed to the charge detrapping related to the liquid–liquid transition of the copolymers. The three peaks all move to lower temperature with an increase of the BA component, indicating that the flexible side groups of butyl acrylate not only have an effect of plasticization on the glass transition and liquid–liquid transition, but also make the trap depth shallower and the detrapping process easier for the ρ and τ peaks. The experimental results confirm that TSDC analysis is very sensitive for investigating the liquid–liquid transition of polymers. The liquid–liquid transition temperature (T LL) of the copolymers follows a type of the Fox equation. Fitting the results gives a T LL of 102°C for polybutyl acrylate.