Structural insight into the interface effect in ferroelectric polymer nanocomposites

The interfaces in complex oxides and semiconductors have been successfully tailored to introduce emergent phenomena and novel functionalities. However, the interfacial approach has not been rationally utilized in electroactive polymer nanocomposites because the origin of the physical, chemical and electrical interaction between nano-fillers and polymer matrix remains essentially unknown. In this work, we present, for the first time, the direct structural analysis on the interfaces and a chemical mapping of the interfacial coupling in the ferroelectric polymer composites at the molecular level by using atomic force microscope infrared spectroscopy (AFM-IR) in combination with phase field simulations and first principles calculations [Y. Liu et al, Adv. Mater. 2020, in press. https://doi.org/10.1002/adma.202005431]. This work reveals a series of unique features of the filler-matrix interfaces, including the local stabilization of all-trans conformation and highly polar and inhomogeneous interfacial regions, which are lacking in the current understanding. The discovery of the size-driven enhancement of local all-trans chain conformation in this work addresses the long-standing controversy surrounding the dependence of the dielectric constants of the composites on the filler size.