Tailoring the Dielectric Performance of Poly(vinylidene fluoride-co-tetrafluoroethylene) through Chemical Grafting via Visible-Light Induced C-F Bond Activation

Poly-(vinylidene fluoride-co-tetrafluoroethylene) (P-(VDF-TFE)), as an excellent electroactive material used in sensors and actuators, has been extensively studied in recent years. Unlike Cl-containing fluoropolymers, it is challenging to regulate the dielectric performance of P-(VDF-TFE) by controllable chemical modification, owing to the inert C-F bonds. In this work, the grafting modification of P-(VDF-TFE) was successfully achieved through C-F bond activation using an Ir-based photoredox catalyst under mild conditions. The influence of the PMMA content on the crystallization and dielectric properties of the graft copolymer was systematically investigated. Pristine P-(VDF-TFE) with 20 mol % TFE units exhibits typical ferroelectric behavior. After introducing low-polarity PMMA side chains, the resulting graft copolymer can be effectively converted into relaxor ferroelectric or linear-like dielectric with dramatically reduced energy loss, thereby broadening its application field. Moreover, the graft copolymer prepared using this photocatalytic system exhibits lower leakage current density compared to the previously reported copper complex catalytic system, indicating a low metal ion residue, which is beneficial to the electric insulation properties.