Synthesis of diamine monomer containing a lactam ring for poly(amide-imide)s

Abstract

Among the high heat resistant polymers, aromatic poly(amide-imide)s have excellent thermal stability, mechanical properties with balanced processability. However they have yellow color caused by formation of charge transfer complex as a disadvantage. For overcome this, introduction of alicyclic rings could be one of solutions which reduce color of polymer film, but it decreases thermal stability. To improve the strength and overcome the weakness, we designed diamine monomer containing spirodilactam which has fastened ring structure. However, the ring was closed incompletely presumably due to the problem of reactivity, so diamine monomer containing a lactam ring on one side and a aliphatic chain on the other side was obtained. A poly(amide-imide) was prepared through polyamidation with diacid monomer having two trifluoromethyl groups symmetrically. The synthesized polymer was found to have low molecular weight because of impurities in diamine monomer and thus showed relatively low thermal stability. On the other hand, $T_g$ and CTE value was good as than expected although the molecular weight was not high enough and aliphatic chain was incorporated. A transparent polymer film with yellow color was obtained by solution casting method.