Synthesis and thermal properties of polyimides containing azomethine linkage for processable high-performance engineering plastics

A new series of polyimides having azomethine functionality in backbone was synthesized by two-steps polycondensation method. Five substituted aromatic diamines—N-(4-aminobenzylidene)-2chloro-6-methylbenzene-1,4-diamine (DA1), N-(4-aminobenzylidene)-2-methoxybenzene-1,4-diamine (DA2), N-(4-aminobenzylidene)-2-methylbenzene-1,4-diamine (DA3), N-(4-aminobenzylidene)-3-methylbenzene-1,4-diamine (DA4) and N,(4-aminobenzylidene)-2-hydroxybenzene-1,4-diamine (DA5)—were prepared and condensed with 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) to obtain poly(azomethine imide). All synthesized polyimides PI(1–5) were fully characterized by elemental analyses, FTIR, 1H-NMR, having amorphous nature and are soluble in dmac, dmf, and dmso, m-cresol due to presence of azomethine functionality. The inherent viscosities and moisture absorption of all polyimides lie in the range of 0.65–0.85 dL gm−1 and 0.68–0.82% respectively. Thermal stability was assessed by 10% weight loss temperature and the degradation temperature of the resultant polymers falls in the ranges from 480–535 °C in nitrogen. The glass transition temperature was in the range of 225–330 °C. Due to above mentioned attractive properties, polyimide-based material are attractive for processable high-performance engineering plastics and starting material for fabrication of new polymers.