The influence of ultrahigh molecular weight polyacrylonitrile on the copolymerization of acrylonitrile with itaconic acid and on the rheological properties of the resulting polyacrylonitrile solutions

In this study, a series of ultrahigh molecular weight polyacrylonitrile (UHMWPAN)/dimethylsulfoxide dilute solutions were produced and they were used afterwards as reaction medium for the synthesis of copolymers of acrylonitrile with itaconic acid by solution polymerization. The influence of UHMWPAN was investigated on the copolymerization and on the rheological behavior of the copolymer solutions. It was found that the presence of UHMWPAN was greatly influential on the copolymerization and the rheological behavior of the solutions. Compared with the polyacrylonitrile solution without UHMWPAN, M η and η increased significantly. The results of shear rheological measurements indicated that the existence of UHMWPAN increased the characteristic relaxation time of polyacrylonitrile solutions. What is more, the polyacrylonitrile solutions containing UHMWPAN exhibited much more evident strain-hardening behavior than the solution without UHMWPAN. It was thus determined that polyacrylonitrile solutions containing a small amount of UHMWPAN are suitable for dry-jet wet spinning and can provide enhanced properties in the preparation of high-performance polyacrylonitrile precursor fiber.