High beta-phase Poly(vinylidene fluoride) Using a Thermally Decomposable Molecular Splint

An additive, 1,4-butadiene sulfone (BDS), which generates H2SO3 by in situ thermal retro-Diels-Alder decompositions, is used for preparing high beta-phase polyvinylidene fluoride (PVDF) films. Because of preferential multiple non-covalent interactions of H2SO3 with all-trans configuration of PVDF, beta-phase PVDF is spontaneously induced without mechanical drawing and/or extensive thermal annealing process. PVDF films cast from PVDF/BDS/water solutions exhibit high beta-phase content (f(beta) = 95%) when the BDS concentration is only c(BDS) =1.0 wt%, which is confirmed by polarized optical microscopy (POM), SEM, Fourier transform infrared spectroscopy (FT-IR), differential scan calorimetry (DSC), and 2D grazing incidence wide-angle X-ray scattering (GIWAXS). Because of the high beta-phase content, PVDF films prepared by using BDS exhibit excellent ferroelectric and piezoelectric properties (E-c = 50 MV/m, P-r = 5 mu C/cm(2), and d(33) = approximate to-25 pm/V). Furthermore, a triboelectric nanogenerator (TENG) developed with high beta-phase PVDF film exhibits enhanced performance as 2.5 times higher than neat PVDF film in output charge density, allowing reliable operation of conventional electronic devices.