New ferroelectric fluoro-terpolymers based on VDF, TrFE, bulky termonomers; high dielectric constant and large electric response at ambient temperature

This paper discusses a new family of ferroelectric polymers with high dielectric constant (>50) and large electrostrictive response (∼5%) at ambient temperature, which is based on a processable semicrystalline terpolymer comprising vinylidene difluoride (VDF), trifluoroethylene (TrFE), and a suitable bulky ter-monomer, including 1,1-chlorofluoroethylene (CFE), chlorodifluoroethylene (CDFE), chlorotrifluoroethylene (CTFE). The terpolymers were prepared by a combination of bulk polymerization process and a borane/oxygen initiator at ambient temperature. The incorporated termonomer units, containing bulky chorine atoms, in the terpolymer reduce the crystalline domain size (without significant reduction of overall crystallinity) and move the ferroelectric-paraelectric (F-P) phase transition to near ambient temperature with a very small activation energy. Some terpolymers exhibited common ferroelectric relaxor behaviors with a broad dielectric peak that shifted toward higher temperatures as the frequency increased, and a slim polarization hysteresis loop at near the dielectric peak (around ambient temperature) that gradually evolved into a normal ferroelectric polarization hysteresis loop with reduced temperature.