Synergistic Dielectric and Mechanical Properties in Poly(1,4-cyclohexylenedimethylene terephthalate)/Silica Composite Films via Solid-State Polycondensation

Abstract

Polymer dielectrics with low dielectric loss and excellent mechanical properties are critical for the development of high-frequency communication and high-temperature reliable electronic devices. This work investigated the synergistic optimization mechanism of the dielectric and mechanical properties in poly(1,4-cyclohexylenedimethylene terephthalate)/silica (PCT/SiO2) nanocomposites through a solid-state polycondensation (SSP) process applied after melt blending, which enabled molecular chain repair and growth. The results demonstrated that SSP effectively repaired the broken macromolecular chains caused by melt blending, increasing the weight-average molecular weight from 2.44 × 104 to 3.35 × 104 g/mol while substantially reducing the carboxyl end group and oligomer content. Meanwhile, the enhanced chain mobility during SSP improved the interfacial compatibility between the polymer matrix and SiO2 nanoparticles. This optimized molecular and interfacial structure synergistically suppressed dipole polarization and ion migration-related dielectric loss, endowing the material with excellent dielectric stability over a wide temperature range (−80 to 160 °C). The key improvements included a significantly weakened temperature dependence of the dielectric constant (Δε′ = 0.36), a loss peak shifted to higher temperatures with reduced intensity, and an increased dynamic Tg of 96 °C. Furthermore, the repaired polymer chains enhanced chain entanglement, reconstructing a continuous and tough stress-transfer network that restored the elongation at break to 126% and the tensile strength to 47 MPa. Therefore, the present design of PCT/SiO2 composite films may provide valuable insights and broad practical prospects for the development of high-performance polymer dielectrics.