Soluble Poly(amide-imide)s from Diamide-Diamine Monomer with Trifluoromethyl Groups

A series of soluble aromatic poly(amide-imide)s (PAIs) was prepared from a new diamide-diamine monomer having biphenyl units with two CF3 groups. The diamide-diamine monomer was polymerized with 2,2 '-bis(trifluoromethyl)benzidine and pyromelltic dianhydride through an imidization reaction to prepare PAIs with a controlled imide/amide bond ratio in the main chains. While the PAIs with the highest imide bond content showed a limited solubility, other PAIs were soluble in polar organic solvents and can be solution-cast into flexible freestanding films. All PAIs exhibited high thermal stability with 5% weight loss temperature (T-d5) from 464 to 497 degrees C in air, and no appearance of glass transition up to 400 degrees C. Notably, the linear coefficient of thermal expansion (CTE) value of the PAI films was linearly decreased with the imide bond content and varied from 44.8 to 7.8 ppm/degrees C.