Effect of the Polyimide Structure and ZnO Concentration on the Morphology and Characteristics of Polyimide/ZnO Nanohybrid Films

A series of polyimide/ZnO nanohybrid films with different ZnO content were prepared from a rigid pyromellitic dianhydride‐4,4′‐diaminodiphenyl ether (PMDA‐ODA) polyimide (PI) and a flexible 3,3′,4,4′‐benzophenonetetracarboxylic acid dianhydride‐4,4′‐diaminodiphenyl ether (BTDA‐ODA) PI with ZnO nanoparticles (3–4 nm). Fourier‐transform infrared (FT‐IR) and X‐ray photoelectron spectroscopy (XPS) depict that the ZnO nanoparticles function as a physical cross‐linking agent with PI through hydrogen bonding between the OH on the ZnO nanoparticles and the CO of the imide groups. ZnO nanoparticles in the rigid PMDA‐ODA matrix cause a larger percentage decrease in the coefficient of linear thermal expansion (CTE) than in the flexible BTDA‐ODA matrix. The BTDA‐ODA/ZnO hybrid films have two transition peaks in dynamic mechanical tan δ curves, but PMDA‐ODA/ZnO hybrid films only have one transition peak. Thermogravimetric analysis reveals that ZnO decreases the thermal degradation temperature (Td) in both hybrid films, but less so in PMDA‐ODA/ZnO films. Transmission electron microscopy (TEM) images reveal that the rigid matrix induces larger particle size (30–40 nm) compared to the flexible matrix (10–15 nm). Illustration of the interaction between ZnO nanoparticles and PI.