Optically transparent and colorless polyimide hybrid films with various clay contents

Poly(amic acid) (PAA) was prepared by the reaction of 4,4-(hexafluoroisopropylidene)diphthalic anhydride with m -xylylenediamine in N , N -dimethylacetamide. Hybrid films were obtained from solutions of the precursor polymer blended with varying amounts of pristine saponite (SPT) clay (0–25 wt%). The cast PAA film was heat-treated at different temperatures to create polyimide (PI) hybrid films, which showed excellent optical transparencies and were almost colorless. The wide-angle X-ray diffraction and transmittance electron microscopy results for the PI hybrid films showed a substantial increase in the agglomeration of the clay particles as the clay loading was increased from 10–25 wt%. This finding suggests that in hybrid materials with low clay contents, the clay particles are better dispersed in the matrix polymer and do not agglomerate significantly. The addition of some amount of clay was sufficient to improve the thermal and oxygen barrier properties of the PI, with a maximum improvement observed at 20 wt% SPT.