A novel POSS-containing polyimide: Synthesis and its composite coating with graphene-like MoS₂ for outstanding tribological performance

Polyimide (PI) stands out for excellent mechanical properties, high thermal stability and flexible property, however, the large friction coefficient and wear rate are still big issues which limit its application. In this work, we successfully synthesized a novel POSS-containing polyimide by the copolymerization of diamine polyhedral oligomeric silsesquioxane (POSS-diamine), pyromellitic dianhydride (PMDA) and 4,4′-Oxydianiline (ODA). Subsequently, the POSS-containing polyimide was mixed with self-made graphene-like molybdenum disulfide (MoS₂) to fabricate composite coating POSS-PI/MoS₂. The tribological properties of POSS-PI/MoS₂ are greatly enhanced via the synergistic effects between POSS and graphene-like MoS₂. The combination of 10 wt.% POSS-diamine and 12 wt.% graphene-like MoS₂ with polyimide leads to 368 % increase of wear life (100 s to 468 s) and 83.3 % decrease of friction coefficient (0.12 to 0.02), especially 15 folds of load carrying capacity (1100 N to 15313 N), compared with pure polyimide. In general, the facile and controllable synthesis procedure, versatile and reproducible combination of POSS-diamine, PMDA and ODA, and relatively high tribological properties of the resulting composite coating, prove this method to be instructive significance for preparing high performance composite coating in future.