Confinement Effects on Crystallization and Curie Transitions of Poly(vinylidene fluoride-<i>co</i>-trifluoroethylene)

Abstract

Nanoscale patterning of piezoelectric and ferroelectric polymers, such as polyvinylidene fluoride (PVdF) and its copolymers with trifluoroethylene (PVdF-TrFE), is increasingly important in organic electronics, memory, and sensing. The nanoscale processing of polymers can lead to materials behavior that is strikingly different from the bulk because of confinement effects. Here we report the effects of confinement of PVdF-TrFE melt-wetted in porous templates of varying pore diameter. PVdF-TrFE is particularly interesting because it possesses a solid-state Curie transition, where both ferro and nonferroelectric phases crystallize into a paraelectric phase. Using modulated differential scanning calorimetry (MDSC), X-ray diffraction (XRD), and broadband dielectric spectroscopy (BDS), we demonstrate that confined PVdF-TrFE crystallizes into an oriented ferroelectric β phase. Both melting and crystallization temperatures decrease with decreasing pore diameter, and the Curie temperature is weakly affected. Results imply that nanoconfinement enhances the formation and orientation of the ferroelectric β phase and could potentially enhance ferroelectricty and piezoelectricity in nanoscale PVdF-TrFE features.