Dielectric Constant, Thermal and Mechanical Properties of Ladder-Like Polypropylsilsesquioxane/Crown Ether-Polyimide Nanocomposites

Ladder-like polypropylsilsesquioxane (LPSQ) with inorganic Si  O  Si double-stranded skeleton in situ growth is incorporated into 18-crown-6-polyimide (CE6-PI) chains by coupling effect of aminopropyltrimethoxysilane to build ladder-like polypropylsilsesquioxane/18-crown-6-polyimide (LPSQ/CE6-PI) nanocomposites. The dielectric constant is evidently decreased, and the strength, toughness, and thermal stability of CE6-PI are greatly improved. A low dielectric constant of 2.71 as well as high tensile strength of 133.7 MPa and toughness of 29.7 MJ m −3 are achieved for the LPSQ/CE6-PI nanocomposite with 23.2 wt% LPSQ. Meanwhile, its glass transition temperature and 5% weight loss temperature exhibit an increase of 23.1 °C and 68.8 °C, respectively, based on CE6-PI. Positron annihilation lifetime spectroscopy, X-ray diffraction patterns, dynamic mechanical analysis, and scanning electron microscope images are applied to investigate the effect of LPSQ on the structure of LPSQ/CE6-PI nanocomposites.