Colorless and transparent polyimide nanocomposite films containing organoclay

A series of colorless and transparent polyimide (PI) nanocomposite films was synthesized from 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and bis(3-aminophenyl) sulfone (APS) with various organoclay contents via solution intercalation polymerization to poly(amic acid)s, followed by thermal imidization. Varying the organoclay loading in the range of 0 to 1.00 wt% produced variations in the thermal properties, morphologies, and optical transparencies of the hybrids. The hybrid films exhibited high optical transparencies and almost no color, with cut-off wavelengths between 330 and 346 nm and very low yellow index (YI) values of 1.78-3.80. The hybrid PI films showed good thermal properties with glass transition temperatures of 236-245 degrees C. Most films did not show significant thermal decomposition below 450 degrees C. It was found that the addition of only a small amount of organoclay was sufficient to improve the thermal properties of the PI films, with maximum enhancements being observed at 0.50 wt% organoclay. Moreover, these PI hybrids also showed low coefficients of thermal expansion (CTE).