UV resistance graft modification of poly(p-phenylene-l,3,4-oxadiazole) fiber with polyhedral oligomeric silsesquioxane

Using the reaction of amino and acyl chloride generated amide bond, poly(p-phenylene-1,3,4-oxadiazole) (p-POD) fiber was pretreated with sulfuric acid solution and was acyl chlorinated with dichloromethane and thionyl chloride. Then octa-ammonium polyhedral oligomeric silsesquioxanes (POSS-NH2) linked on the fiber surface with the amide bond, which was as UV absorbent to retard UV photoaging. Under the existing experimental conditions, a higher sulfuric acid solution concentration, a higher temperature or a longer time was beneficial for increasing the fixed amount of POSS and prevent the UV accelerated aging of the fiber. The surface morphology, tensile strength, crystallinity, degree of orientation of fibers, and intrinsic viscosity of polymer solution were characterized in detail. This graft process with POSS-NH2 introduced silicon elements onto the fiber surface. Changes in the surface morphology and chemical composition are not obvious, except that part of the oxadiazole rings were opened. After UV-accelerated aging, the degree of orientation and the crystallinity of the fiber and the intrinsic viscosity of polymer solution were well maintained. The condensed and macromolecular structures of the fiber were well protected.