Large intrinsic piezoelectricity in intramolecular modified relaxor ferroelectric polymers near the morphotropic phase boundary
Piezoelectric materials interconvert mechanical and electrical energy, but piezoceramics are brittle while PVDF-based ferroelectric polymers exhibit low piezoelectric coefficients (d33 ≈ -30 pC N-1). Chemical modification via morphotropic phase boundary (MPB) engineering has raised d33 in P(VDF-TrFE) to -63.5 pC N-1, and to -69 pC N-1 with stretching, but intrinsic piezoelectricity in relaxor terpolymers remains limited. Here, relaxor ferroelectric P(VDF-TrFE-CFE) with varying C=C double bond (DB) content is synthesized via dehydrochlorination. Structural and electrical characterization reveals that increasing DB content stabilizes long-range ferroelectric order while suppressing short-range relaxor characteristics, forming a trans/helix phase boundary. At a critical DB content of 2.0 mol%, a markedly enhanced intrinsic d33 of -129.0 pC N-1 is achieved, outperforming previous MPB approaches. This finding addresses the fundamental bottleneck of low piezoelectric response in flexible ferroelectric polymers and provides a viable route for high-performance wearable electromechanical devices.