Flexible and Transparent High-Dielectric-Constant Polymer Films Based on Molecular Ferroelectric-Modified Poly(Vinyl Alcohol)

Organic ferroelectrics with high dielectric constant have received substantial attention for sustainable and flexible energy storage. Here, we report a high-κ dielectric, optically transparent, mechanically strong and flexible dielectric polymer produced by in situ formation of biaxial ferroelectric-molecule-modified poly­(vinyl alcohol) (PVA). The composite film was fabricated by solution casting of a PVA solution containing water-soluble dielectric crystals [Hdabco]­ClO₄. Atomic force microscopic and polarized optical microscopic studies showed a uniform dispersion of TEDA.C crystals with tunable rod-like or dendritic microstructures in the PVA matrix. Because of the good compatibility and hydrogen bonds between PVA and TDEA.C, the modified PVA films presented a significant enhancement of the dielectric constant and energy storage density by 10–100-fold over neat PVA. The polarization-electric loops indicated that the PVA composite films possessed increased saturation polarization in comparison to neat PVA film. The remnant polarization of PVA composite films was improved by around 3200 times with 9 wt % TEDA.C. Also, the TEDA.C@PVA films exhibited 85% transparency throughout the visible spectrum, 116% increase in storage modulus, and 274% elongation at fracture. These unprecedented high-κ dielectric, optical, and mechanical properties may break the restrictions in the applications of traditional ferroelectric materials and greatly expand the usage of dielectric polymers in broad fields.