Polymer dielectrics generally have comparatively low dielectric constant, operating temperatures, and/or high dielectric loss, which limits their uses especially in harsh environment. In this article, a novel trilayered nanocomposite film (TNF) was constructed via solution-casting and, subsequently, hot-pressing process, which was composed of two outer layers of polyvinylidene fluoride (PVDF, high dielectric constant) and a middle layer of polymethyl methacrylate (PMMA, high glass transition temperature, T-g). The two outer layers of TNF were filled with barium strontium titanate nanoparticles to further increase the dielectric constant of PVDF. The PMMA in the middle layer was used to largely suppress the dielectric loss and simultaneously improve the temperature tolerance of TNF. Results show that the introduction of PMMA induced oriented crystal formation in the interface regions between PVDF and PMMA components. Moreover, most of the impurity ions were dramatically immobilized by partly oriented alpha crystals and high T-g PMMA layer until the temperature exceeded 120 degrees C. Therefore, the TNFs showed a high-temperature tolerance and notably decreased loss, which are promising for widespread energy storage applications where harsh working conditions are present. (c) 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019