Microwave irradiation was successfully applied to condensate aromatic diamines with linear aliphatic dicarboxylic acids through the Yamazaki phosphorylation reaction. Succinic, adipic, suberic, sebacic, and fumaric acids were reacted with p-phenylenediamine or 2,5-bis(4-aminophenyl)-3,4-diphenylthiophene to produce P-series and T-series of partially aromatic polyamides. Medium to high yields (60–100%) were achieved after a very short polymerization time (30 or 40 s). The intrinsic viscosity of products range from 10 to 80 mL g–1. The solubility of the T-series of polyimides has been improved due to the presence of the bulky phenylated diamine moiety. The chemical structure of the polyamides was confirmed by FTIR, 1H and 13C NMR spectroscopy. Thermal properties were investigated using DSC and TGA techniques under inert atmosphere. Polyfumaramides (PF and TF) were recognized to be the most thermally stable polyamides (the highest IPDT values). However, these two polymers as well as polysuccinamides (P2 and T2) showed the lowest index of intrinsic thermal stability (ITS), i. e., although they have the highest refractoriness (the highest char yields), they began to decompose at relatively low temperatures. A crosslinking mechanism was proposed for the similar thermal behavior of the fumaramides and succinamides.
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Pourjavadi et al. (1999) studied this question.