In situ thermal synthesis of novel polyimide nanocomposite films containing organo-modified layered double hydroxide: morphological, thermal and mechanical properties

An organic-inorganic hybrid compound comprised of a Zn/Al layered double hydroxide (LDH) intercalated with citric acid (LDH-CA) was dispersed in polyimides (PIs) with an N-benzonitrile side group, through in situ polymerization. At first, 3-(bis(4-aminophenyl)amino)benzonitrile as a diamine monomer was synthesised and then it was reacted with 4,4'-benzophenone tetracarboxylicdianhydride via a thermal imidization method to form processable PIs. To improve the thermal and mechanical properties and also to avoid the aggregation of LDH particles in the polymer matrix, a small amount of LDH-CA (1, 2, 4 wt%) was added to the synthesized PI. The resulting materials were characterized by Fourier transform-infrared spectroscopy, X-ray powder diffraction, thermogravimetric analysis (TGA), field emission-scanning electron microscopy, and transmission electron microscopy (TEM) techniques. TEM results showed that the LDH-CA nanolayers were dispersed in PI matrices. The mechanical and thermal properties of the synthesized composites are effectively enhanced by the incorporation of 2 wt% LDH-CA in the polymer matrix. For the PI/LDH-CA nanocomposites, a maximum degree of tensile strength is observed at a LDH-CA loading of 2 wt%, corresponding to an almost 32% increase in tensile strength compared to the pure PI.