Synthesis and characterization of poly(amide-imide)s with high Tg and low CTE derived from isomeric amide-containing diamines

• Two isomeric amide-containing diamines were synthesized and PAI films were prepared. • The effect of different amide structures on the performance of PAI films were investigated. • The film possess good thermal properties with Tg value are more than 400 °C. Two series of poly(amide imide)s (PAIs) based on two novel isomeric amide-containing diamine monomers and different commercial aromatic dianhydrides were synthesized via thermal imidization. These PAIs exhibited excellent T g s ranging from 368 to 431 °C, low coefficients of thermal expansion (CTE) of 6.7–47.2 ppm/K, and good 5% weight loss temperatures ( T d5% s) in N 2 of 494–540 °C, which was attributed to the introduction of rigid backbone and strong intermolecular hydrogen bonding resulted from amide bond. In particular, PAI-1a and PAI-1b displayed well-balanced performance with T g s in the range of 419–431 °C, CTE in the range of 6.7–9.0 ppm/K, and mechanical properties with tensile strengths of 116–125 MPa, tensile moduli of 8.4–8.7 GPa, which could be probably used in flexible displays. In addition, the effects of two isomeric monomers on the properties of films were compared, and it was found that PAI-(1 – 3)a showed higher T g, T d5% and CTE, but lower tensile strength and transparency than PAI-(1 – 3)b .