Effect of phosphoric acid molarity on the structural,thermal,mechanical,and electrical properties of polyimide/polyaniline nanocomposites

In this paper, we used two monomers, 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) and m,m'-diaminobenzophenone (m, m’-DABP), to produce polyamide acid and then converted it to polyimide (PI). The effects of phosphoric acid (H₃PO₄) molarity (1, 2, and 3 M) on the structural, thermal, mechanical, and electrical characteristics of the polyimides/polyaniline (PI/PANI) nanocomposites were studied. Two sharp reflection peaks were developed by the addition of PANI to PI. When 3 M H₃PO₄ is added, the crystalline sharp peak loses some of its intensity. The complex formation of PI/PANI-H₃PO₄ was confirmed by Fourier transform infrared spectroscopy studies. The surface morphologies of the H₃PO₄ complex with nanocomposites were investigated by using a scanning electron microscope. From differential scanning calorimetry studies, the glass transition temperatures of nanocomposites decrease dramatically with an increase in H₃PO₄. Microhardness, flexural strength, and young modulus all dropped as acid molarity increased, although elongation at break increased as H₃PO₄ molarity increased. After the addition of H₃PO₄, a drop in the dielectric constant and an increase in ionic conductivity were observed.