UCST-Type Phase Separation and Crystallization Behavior in Poly(vinylidene fluoride)/Poly(methyl methacrylate) Blends under an External Electric Field

Abstract

The effects of an electric field on upper critical solution temperature (UCST) phase separation and crystallization behavior in binary blends of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) were investigated by means of time-resolved small-angle light scattering (SALS) and polarizing optical microscopy (POM). The lower critical solution temperature (LCST) phase separation curve of this blend could not be measured experimentally due to thermal decomposition caused by too high LCSTs. However, the UCST-type phase separation curve was observed from SALS measurements to shift toward higher temperatures under the electric field. In the temperature range above the UCST (150 °C ≤ T ≤ 158 °C), the electric field reduces the overall crystallization rate in the neat PVDF and, in contrast, increases the crystallization rate in 95/5, 90/10, and 85/15 PVDF/PMMA blends. In the temperature range below the UCST (130 °C ≤ T ≤ 143 °C), the electric field also increased the overall crystallization rate in the 80/20 and 70/30 PVDF/PMMA blends. POM images were also used to investigate the effect of the electric field on the overall melt-crystallization rate, nucleation rate, and crystalline morphology in PVDF/PMMA blends.