Fluorine-free strongly dipolar polymers exhibit tunable ferroelectricity.

Current research on ferroelectric polymers centers predominantly on poly(vinylidene fluoride) (PVDF)–based fluoropolymers because of their superior performance. However, they are considered "forever chemicals" with environmental concerns. We describe a family of rationally designed fluorine-free ferroelectric polymers, featuring a polyoxypropylene main chain and disulfonyl alkyl side chains with a C3 spacer: −SO2CH2CHRCH2SO2− (R = −H or −CH3). Both experimental and simulation results demonstrate that strong dipole-dipole interactions between neighboring disulfonyl groups induce ferroelectric ordering in the condensed state, which can be tailored by changing the R group: ferroelectric for R = −H or relaxor ferroelectric for R = −CH3. At low electric fields, the relaxor polymer exhibits electroactuation and electrocaloric performance comparable with those of state-of-the-art PVDF-based tetrapolymers. Editor's summary: The vast majority of ferroelectric polymers are based on poly(vinylidene fluoride) (PVDF) chemistry because of their superior performance. However, concerns about fluorine-based "forever chemicals" have encouraged searches for alternative materials. Huang et al. investigated the synthesis, structure, ferroelectricity, and electromechanical and electrocaloric effects of side-chain polymers without fluorine or mesogenic groups. They developed a relaxor ferroelectric liquid crystal polymer that features highly polar disulfonyl groups in which the side chains form a layered structure. Their material demonstrates superior electrostriction and electrocaloric properties at low electric fields comparable to state-of-the-art PVDF-based tetrapolymers. —Marc S. Lavine [ABSTRACT FROM AUTHOR]