Synthesis and properties of colorless polyamide films with high thermal resistance and dimensional stability

Polyamides (PAs) based on terephthaloyl chloride and a series of aromatic diamines were synthesized; PA films were prepared by solution casting without mechanical stretching to produce high-performance films with good optical transparency and dimensional stability. The PA films displayed high heat resistance with glass transition temperatures (Tg) of 342–399°C. Good mechanical properties were obtained with tensile modulus and strength up to 5.38 GPa and 195.4 MPa, respectively. Coefficient of thermal expansion of the as-cast PA films achieved to an ultralow value of 8.3 ppm °C⁻¹ and could be tailored in a wide range as a function of the macromolecular composition. The series of PA films showed a transparent and colorless feature, with the cutoff wavelength in the range of 355–365 nm. The data were discussed from the perspective of structure–property relationship, may give helpful knowledge for the topic of PA chemistry, and this method could provide an alternative for the production of high-performance colorless polymer films.