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 aci d (XabX), bis(4-nitrophenyl) isophthalate (XccX), piperazine (YddY), and 4- aminobenzohydrazide (YefY), using the condensing agent diphenyl(a,3-dihydro -2-thioxo-3-benzoxazolyl)phosphonate (1). The polymerization was carried ou t by mixing the dicarboxylic acid, diester, condensing agent 1, and triethy lamine (TEA) in N-methyl-2-pyrrolidinone (NMP) for 3 h at room temperature, followed by adding piperazine and aminobenzohydrazide at -15 degrees C. Th e mixture was stirred at -15 degrees C for 2 h, room temperature for 24 h, and 70 degrees 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, measu red at a concentration of 0.5 g/dL at 30 degrees C. The feasibility of the formation of the ordered polymer from three nonsymmetric monomers was demon strated by studying the model reactions in detail. Furthermore, the authent ic ordered and random polymers were prepared to verify the structure of the ordered polymer. The microstructures of the polymers obtained were investi gated by H-1 and C-13 NMR spectroscopy, and it was found that the polymer o btained by direct polycondensation has the expected ordered structure.