Synthesis and properties of organosoluble polyimide/clay hybrids

A soluble polyimide prepared from 7,7′-bis(4-aminophenoxy)-4,4,4′,4′-tetramethyl -2,2′-s pirobichroman and 4,4′-hexafluoroisopropylidenediphthalic anhydride was mixed with organo-modified montmorillonite or synthetic mica in N,N-dimethylacetamide. The content of the clay minerals was 1, 2, and 4 wt %, respectively. Transparent, flexible, and tough films could be cast from the hybrid solutions. The hybrid films were characterized with wide-angle X-ray scattering (WAXS), transmission electron microscopy, thermomechanical analysis, thermogravimetric analysis, and differential scanning calorimetry. The WAXS results revealed that the montmorillonite was dispersed more homogeneously than the synthetic mica in the polyimide matrix. In both polyimide/clay hybrids the addition of clay caused thermal expansion coefficients to decrease, and the thermal stability was slightly enhanced.