Large piezoelectricity in crosslinked ferroelectric polymers

Ferroelectric polymers exhibit numerous advantages for flexible and wearable electromechanical applications. However, their piezoelectric coefficient d₃₃ remains relatively low while most previous approaches to improve d₃₃ mainly focus on intramolecular engineering. Other than using intramolecular approaches, here we describe an intermolecular crosslinking strategy to achieve markedly enhanced d₃₃ of -95.0 picocoulombs per newton in crosslinked ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) copolymers. First-principles calculations reveal that intermolecular crosslinking creates strong local conformational heterogeneity facilitating ease of bond rotation near the crosslinking sites, which leads to a flattened energy landscape, resulting in substantially improved d₃₃ response. We show that crosslinking enabled by solution casting process enhances piezoelectric properties across a variety of crosslinking agents. Our work offers a facile platform for rational modulation of piezoelectricity of ferroelectric polymers, representing a crucial step towards large-scale manufacturing of lightweight, flexible, and scalable ferroelectric polymers for developing high-performance electromechanical devices.