Strain-Induced Polar Interfaces in Ferroelectric Polymer Nanocomposites

The development of the all-trans chain conformation at polymer matrix-filler interfaces is essential for enhancing the dielectric constant, electrocaloric effect, and electromechanical response in ferroelectric polymer nanocomposites, which have been extensively explored for a wide range of applications, including high-energy-density film capacitors, electrocaloric coolers, and electromechanical devices. However, the origin of the interfacial polar structure remains unclear. Here, using high-resolution transmission electron microscopy combined with density functional theory calculations and molecular dynamics simulations, this study reveals that a distorted all-trans conformation of poly(vinylidene fluoride) (PVDF) can be induced by the strain at the organic-inorganic interfaces within the polymer composites. This study argues that the substantial difference in lattice parameters between the inorganic filler and the polymer matrix plays a crucial role in the formation of the interfacial strain. These results offer insights into the origin of the polar interfaces in ferroelectric polymer nanocomposites, which may enable the investigation of the mechanism of strain formation from a new perspective.