HETEROGENEITY OF POLY-p-PHENYLENE-1,3,4-OXADIAZOLE.

The authors describe the results of an investigation of heterogeneity parameters and the temperature-concentration boundaries of phase changes in sulfuric acid solutions of POD by the turbidity spectrum method. Synthesis of the POD is carried out in an oleum medium, and the heterogeneity of the polycondensation solutions obtained can depend not only on the special features of carrying out the polycondensation process and the purity of the original monomers, but also on the oleum. Experimental results show that the heterogeneity of spinning dopes is mainly caused by impurities contained in the starting raw materials. Heterogeneity of concentrated POD solutions (above 13%) is connected with the formation of crystal solvates. The melting points of the crystal solvates in POD solutions depend on the polymer content of the solution, the molecular weight of the POD, the sulfuric acid concentration, and the nature of the modifying components.