Polymer/organosilica nanocomposites based on polyimide with benzimidazole linkages and reactive organoclay containing isoleucine amino acid: Synthesis, characterization and morphology properties

Polyimide–silica nanocomposites are attractive hybrid architectures that possess excellent mechanical, thermal and chemical properties. But, the dispersion of inorganic domains in the polymer matrix and the compatibility between the organic and inorganic phases are critical factors in these hybrid systems. In this investigation, a reactive organoclay was prepared via ion exchange reaction between protonated form of difunctional l-isoleucine amino acid as a swelling agent and Cloisite Na+ montmorillonite. Amine functional groups of this swelling agent formed an ionic bond with the negatively charged silicates, whereas the remaining acid functional groups were available for further interaction with polymer chains. Then organo-soluble polyimide (PI) have been successfully synthesized from the reaction of 2-(3,5-diaminophenyl)-benzimidazole and pyromellitic dianhydride in N,N-dimethylacetamide. Finally, PI/organoclay nanocomposite films enclosing 1%, 3%, 5%, 7% and 10% of synthesized organoclay were successfully prepared by an in situ polymerization reaction through thermal imidization. The synthesized hybrid materials were subsequently characterized by Fourier transform infrared spectroscopy, X-ray diffraction, electron microscopy, and thermogravimetric analysis techniques. The PI/organoclay nanocomposite films have good optical transparencies and the mechanical properties were substantially improved by the incorporation of the reactive organoclay.

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► A reactive organoclay was formed using l-isoleucine amino acid as a swelling agent.
► Polyimide was synthesized from benzimidazole diamine and pyromellitic dianhydride.
► Imide and benzimidazole groups assured the thermal stability of the nanocomposites.
► Nanocomposite films were prepared by an in situ polymerization reaction.
► The TEM micrographs of nanocomposites revealed well-exfoliated structures.