Synthesis of Ordered Polymer by Direct Polycondensation. 9. Ordered Poly(amide−acylhydrazide−amide) from Three Nonsymmetric Monomers

An ordered (−ccfebaddabef−) poly(amide−acylhydrazide−amide) was prepared by the direct polycondensation of 5-(3-carboxypropyl)-2-isopropoxybenzoic acid (XabX), bis(4-nitrophenyl) isophthalate (XccX), piperazine (YddY), and 4-aminobenzohydrazide (YefY), using the condensing agent diphenyl(2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphonate (1). The polymerization was carried out by mixing the dicarboxylic acid, diester, condensing agent 1, and triethylamine (TEA) in N-methyl-2-pyrrolidinone (NMP) for 3 h at room temperature, followed by adding piperazine and aminobenzohydrazide at −15 °C. The mixture was stirred at −15 °C for 2 h, room temperature for 24 h, and 70 °C for 4 d in the presence of 1-hydroxybenzotriazole (HOBt). The resulting polymer gave an inherent viscosity of 0.20 dL/g in NMP, measured at a concentration of 0.5 g/dL at 30 °C. The feasibility of the formation of the ordered polymer from three nonsymmetric monomers was demonstrated by studying the model reactions in detail. Furthermore, the authentic ordered and random polymers were prepared to verify the structure of the ordered polymer. The microstructures of the polymers obtained were investigated by 1H and 13C NMR spectroscopy, and it was found that the polymer obtained by direct polycondensation has the expected ordered structure.