Thermomechanical characterization of thermoplastic polyimide to improve the chain interaction via crystalline domains

In a previous study on polyimides, we incorporated 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 decrease rigidity. In this report, we explore the behavior of crystalline regions provided by the organized packing of polyethylene oxide into the formerly characterized polymers. The polymers were designed to exhibit thermal properties in between those of conventional aromatic polyimides and polymers with wholly aliphatic ether diamine links, with a target to improve the mechanical characteristics. Through dynamic mechanical analysis and differential scanning calorimetry, it is shown that the incorporation of polyethylene oxide diamine and the removal of methyl pending groups serve to improve the organized packing of the chains. All of this allows for a broader range in tenability of thermal and mechanical properties of the polyimide. Furthermore, the crystalline regions are an important component to maintain the temperature stability of polyimide while maintaining the processability. The polymers are characterized by Fourier‐transform infrared spectroscopy, thermomechanical and calorimetric analysis, microhardness measurements, tensile testing, and wide‐angle X‐ray scattering. POLYM. ENG. SCI., 59:1919–1932, 2019. © 2019 Society of Plastics Engineers