Construction of polyimide films with excellent dimensional stability and toughness via incorporating point-to-face multi-coordination structure

Flexible polyimide (PI) films with simultaneously excellent dimensional stability and toughness were vital for the application and reliability of flexible display. Thus, in this paper, we designed a novel PI film containing point-to-face multi-coordination structure. The coordination structure was constructed by introducing Cu2+ and benzimidazole ligands into polyimides, and the existence of the point-to-face multi-coordination was proved. Excellent toughness and dimensional stability under high temperature, multiple heating-cooling cycles, and cyclic tension of PI films were realized, resulting from destruction and rapid reconstruction of point-to-face multi-coordination structure with the advantage of large bonded areas. Compared with PI without Cu2+ (PICu0), the thermal expansion coefficient of PI with 20mol% Cu2+ (PICu20) reduced 94%, and the tensile strength, percentage of breaking elongation and fracture energy of PICu20 increased by 40%, 45% and 174%, respectively. Furthermore, the water absorption of PICu films dropped and the dielectric breakdown strength was maintained.