The effect of the ring opening polymerization and chain spacing on the coefficient of thermal expansion and modulus of polyimide

The features of norbornene (NE) cross-linked polyimide (PI) were investigated as the ratio of the norbornene monomer was varied. The coefficient of thermal expansion and modulus are important parameters of materials used in the microelectronic industry. Therefore, in this study, 5-norbornene-2, 3-dicarboxylic acid (NE) was introduced as a crosslinking agent to increase the thermal stability at elevated temperatures. 4,4′-Benzophenonetetracarboxylic dianhydride was utilized as a dianhydride and 4,4′-diaminodiphenyl ether was introduced as a diamine monomer. By changing the ratio of each monomer, we were able to control the spacing of the chain and ring opening polymerization, which resulted in improved properties. Each sample was thermally cured which led to a ring opening mechanism of the norbornene through the reverse Diels-Alder reaction. Thermal mechanical analysis was utilized to determine the coefficient of thermal expansion and dynamic mechanical analysis was used to determine the storage modulus (ε′) and loss modulus (ε'') of the PI film.