Poly(squaryl amides)

The solution polycondensation of squaric acid with p-phenylenediamine in selected protic, aprotic or strongly acidic solvents furnishes linear polyamide structures possessing units with 1,2- as well as those with 1,3-orientation of the substituent links on the four-membered ring system. The relative occurrence of these two unit types as assessed by infra-red spectroscopy depends on the basicity of the medium, the extent of 1,2-orientation decreasing with increasing solvent basicity. The same type of polyamide results from a solution polycondensation of the diamine with diethyl squarate. These findings, contradicting earlier results of other workers, are in accord with more recent non-polymeric squaric acid amidation studies. A reference polyamide with maximum content of units possessing the 1,2-substituent orientation is synthesized from p-phenylenediamine and squaryl dichloride under low temperature solution polymerization conditions. Polymer inherent viscosities range from about 10 to 30ml/g, highest values being obtained under conditions of homogeneous polymerization.