Synthesis and characterization of new soluble polyamides derived from 2,6‐bis(4‐aminophenyl)‐3,5‐dimethyltetrahydro‐4H‐pyran‐4‐one

A new oxypyrone diamine, 2,6‐bis(4‐aminophenyl)‐3,5‐dimethyltetrahydro‐4H‐pyran‐4‐one (DAPP), was prepared from 4‐nitrobenzaldehyde and 3‐oxa‐n‐pentane in a two‐step reaction with a high yield and a high purity. Aromatic polyamides were obtained from this novel condensation monomer and several diacid chlorides through the conventional low‐temperature solution method in N,N‐dimethylacetamide. Polycondensation results were consistent with a high reactivity for DAPP because high yields and high molecular weight polyamides were obtained with inherent viscosities up to 1.8 dL/g. The reactivity of DAPP was also estimated with theoretical calculations from computer programs for molecular simulation, with orbital and charge factors considered. The polymers showed improved solubility in organic solvents, relative to conventional wholly aromatic polyamides, and high glass‐transition temperatures (from differential scanning calorimetry) over 270 °C. However, the thermal resistance, as estimated by thermogravimetric analysis, was lower than that of conventional aromatic polyamides; nevertheless, decomposition temperatures well beyond 300 °C were observed in nitrogen and air.