Geometric constraint annealing leading to β-phase enhancement of electrospun poly(vinylidene fluoride)

The β-phase poly(vinylidene fluoride) (PVDF) has attracted much interest as energy harvesting materials in powering flexible devices for its promising piezoelectric and pyroelectric properties. Intensive stretching and high electrical field are introduced in the electrospinning process, which contributes to alignment of PVDF molecular chains and results in the PVDF β-phase crystallization from solution. Also the slim cylinder-like geometry of the electrospun fibers has high surface-to-volume ratio and increases the inhomogeneous nucleation of PVDF. A proper compression stress during annealing will increase the mobility of molecular chains and lead to growth of the β phase.