Synthesis and characterization of a new series of polyimide- nanocomposite reinforced by modified layered silicate based on 3,3′,4,4′-biphenyl tetracarboxylic dianhydride

In this research, three new reinforced nanocomposites polyimides films (9a-c) by modified organoclay (MMT) (8) varying from 1, 3 & 5 wt% were successfully prepared by in situ polymerization technique through the thermal imidization up to 200°C into a solution of N, N'-dimethyl acetamide (DMAc). Synthetic polyimide (4) that used as a matrix was prepared through the polycondensation reaction of 4,4´-diamino diphenyl sulfone (1) and 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (BPDA) (2) into N, N'-dimethyl acetamide as solvent. Montmorillonite Na+-organoclay (MMT) (5) was modified via a cationic exchange method by the reaction between the sodium cations of Na+-MMT clay and quaternary alkyl ammonium ions of p-amino benzoic acid (6) (p-ABA) as intercalation agent. Resulting polyimide chains (4) diffused into the interlayer of modified organoclay layers (8) by intercalation polymerization technique. The resulting nanocomposite films (9a-c) containing 1, 3 & 5 wt% of modified organoclay prepared by casting method were characterized by Fourier-Transform infrared (FT-IR) spectroscopy, wide-angle powder X-ray diffraction (XRD), scanning electron microscopy (SEM). Results by thermo gravimetric analysis (TGA) indicated shown a sharp increase into thermal stability of their nanocomposites as compared to pristine polyimide.