Deep Eutectic Solvent—A Novel Additive to Induce Gamma Crystallization and Alpha‐to‐Gamma Phase Transition of PVDF

Adding additives is the most convenient and effective way to induce polar poly(vinylidene fluoride) (PVDF) crystals which exhibit excellent ferroelectronic, piezoelectric, and dielectric properties. In this work, a kind of environmentally friendly additive, deep eutectic solvent (DES), is introduced to induce the crystallization of polar phases and accelerate theα‐to‐γphase transition, which enables the fraction ofγ(γ′)‐phase crystals to exceed 90% in the PVDF/DES composite containing only 1 wt% DES. The ion–dipole interaction between PVDF and hydrogen bond acceptor in DES induces the polar molecular conformation, thus bringing about the formation of polar phase crystals. However, hydrogen bond donor promotes the dispersion of hydrogen bond acceptor in PVDF matrix, contributing to the flexibility of the composites.