Polyhedral oligosilsesquioxane-modified boron nitride enhances the mechanical properties of polyimide nanocomposites

A novel high-strength polyimide (PI) nanocomposite film was designed and constructed by the copolymerization of epoxidized polyhedral oligomeric silsesquioxane-modified hexagonal boron nitride and polyamic acid (PAA). The composite filler (EPPOSS@Gh-BN) was composed of silane coupling agent KH550 modified hexagonal boron nitride (Gh-BN) and epoxidized polyhedral oligomeric silsesquioxanes (EPPOSS), which improved not only the dispersion of the h-BN but also the effective interfacial stress transfer, leading to an enhanced mechanical strength of the resultant PI nanocomposite film of 114 MPa even with a slight EPPOSS@Gh-BN loading of 0.30 wt%, and the storage modulus was increased by more than 30% to 4 GPa compared to pure PI. Meanwhile, the PI/EPPOSS@Gh-BN nanocomposite has better heat transfer performance, higher hydrophobicity, lower dielectric properties, and higher heat stability than pure PI, and is therefore expected to provide an ideal platform for the development of highly flexible electronics in the future.