Ultrahigh Piezoelectric Coefficients Achieved by Tailoring the Sequence and Nano-Domain Structure of P(VDF-TrFE)

During past decades, the construction of morphotropic phase boundary (MPB) behavior in ceramic-based relaxor ferroelectrics has successfully led to a significant enhancement in the piezoelectric coefficient for actuators, transducers, and sensors application. However, MPB-like behavior is achieved only in the ferroelectric state in flexible ferroelectric polymers such as poly(vinylidene fluoride-trifluoroethylene) with the highest piezoelectric coefficients of ≈-63.5 pC/N, due to the lack of a rational design in polymer chain structure and composition. Here, the study reports the first MPB-like behavior observed in a relaxor ferroelectric polymer synthesized by fully hydrogenating poly(vinylidene fluoride-chlorotrifluoroethylene), which are primarily linked in a head-to-head/tail-to-tail manner, and trifluoroethylene units are randomly dispersed along the molecular chain. The unique polymer chain structure is found to be responsible for the formation of conformations disorder, thus strong relaxor behavior, and phase transition from an all-trans conformation to 3/1 helix, thus inducing phase boundary behavior. As a result, an outstanding longitudinal piezoelectric coefficient of -107 pC/N, more than five times higher than that of commercial poly(vinylidene fluoride) (-20 pC/N), is observed. This work opens up a new gate for next-generation high-performance flexible devices.