Thermomechanical characterization of thermoplastic polyimide–polyurea to improve the chain interaction via internal hydrogen bonds

Recently, we have studied polyimides (PIs) synthesized by incorporating an aromatic diamine monomer with a methylene linker, 4,4′‐methylenebis(2,6‐dimethylaniline), to make a robust main chain along with aliphatic polyetherdiamine backbone linkers to reduce rigidity. In this report, we incorporate a urea linkage into these materials in order to observe the effect of additional hydrogen bonding. The polymers are designed to exhibit thermal properties in between those of conventional aromatic PIs and polymers with wholly aliphatic ether diamine links. Herein, we demonstrate that the addition of 1,6 hexamethylene diisocyanate and the increase of hydrogen bonds at the urea linkage can be used to improve the thermal and mechanical properties of the PI. Furthermore, the imide ring is an important component to maintain the thermal stability characteristics in polyimide–polyurea hybrids. The polymers were characterized by FTIR, thermomechanical and calorimetric analysis, microhardness, and tensile testing. POLYM. ENG. SCI., 59:1948–1959, 2019. © 2019 Society of Plastics Engineers