Journey of Electroactive β-Polymorph of Poly(vinylidenefluoride) from Crystal Growth to Design to Applications

Electroactive polymers are ideal candidates for dielectric and piezoelectric applications due to their very high breakdown strength, good flexibility, and ease of processing. Among the various polymers, poly(vinylidenefluoride) (PVDF) is of special interest due to potential applications in sensors, capacitors, actuators, etc. PVDF exists in four different crystalline phases (α-, β-, γ-, and δ-phases). Among these, the electroactive β-phase is very important for dielectric and piezoelectric applications. In the recent past, research has been focused on obtaining the maximum amount of electroactive β-polymorph in PVDF. The piezoelectric and dielectric properties of PVDF are influenced by the amount and the possible orientation of the polar β-phase. However, the effect of orientation on the electroactive β-phase in the field direction toward improving dielectric and piezoelectric applications is still not clear. This review attempts to bring in mechanistic insights into various processes that induce the electroactive β-phase, orientation, and correlation with dielectric and piezoelectric properties in PVDF-based composites. Some of the challenges and possible solutions for the future fabrication of piezoelectric materials are also emphasized.