Soluble and transparent poly(amide-imide)s with ultra-low coefficients of thermal expansion

Abstract

Transparent and soluble poly(amide-imide)s (PAIs) with high dimensional stability were synthesized from the monomer consisting of a dibenzodioxin skeleton. The diimide-dicarboxylic acid monomers were synthesized from dibenzo-dioxin tricarboxylic acid anhydride and trimellitic anhydride with 2,2′-bis(trifluoromethyl)benzidine, and a series of PAIs were prepared from the polymerization of the diacid monomers with 2,2′-bis(trifluoromethyl)benzidine. All the polymers were soluble in polar organic solvents and can be solution-cast into nearly colorless and flexible freestanding films. The obtained PAI films possessed high T d5 value (469–481 °C in N 2 ) and high transparency (∼88% transmittance at 550 nm). Interestingly, PAIs prepared in this study exhibited high thermo-dimensional stability with low CTE values as low as 1.3 ppm/ ° C. • Soluble poly(amide-imide)s are synthesized from the rigid ladder-type monomer. • The freestanding polymer films show low CTE values around 2 ppm/ ° C. • The amorphous polymers having dibenzo-dioxin units have high optical transparency.