Resultful synthesis of polyvinyltetrazole from polyacrylonitrile

Abstract

The novel functionality of aromatic tetrazole derivatives with high nitrogen content predetermines a great interest to tetrazole-containing polymers. Poly(5-vinyltetrazole) (PVT) is one of the most attractive polymers containing tetrazoles. PVT with a broad range of tetrazole-group contents was conveniently and efficiently synthesized by a cyano-tetrazole conversion of different molecular weight polyacrylonitriles at tetrazole-cyclization temperatures from 60 to 120 °C. The dependency of the tetrazolation yield, tetrazole content, intrinsic viscosity, solubility, film formability, and thermal properties of the PVT on the cyclization temperature was studied by IR and UV–Vis spectroscopies, elemental analysis, DSC, and thermogravimetry techniques. The PVT exhibits much higher intrinsic viscosity than original polyacrylonitrile. The polymer obtained is a special polymer containing both vinyltetrazole and acrylonitrile units. The higher the cyclization temperature, the higher the tetrazole content is. PVT will exhibit higher tetrazolation yield and larger tetrazole content if the polyacrylonitrile of higher molecular weight is served as initial polymer. The highest tetrazolation yield and largest tetrazole content are up to 98.0% and 97.5 mol%, respectively, which are much higher than corresponding literature results. All of the PVTs are almost completely soluble in highly polar solvents such as DMF, NMP, DMSO, and HNO 3, especially the PVT containing 18 mol% tetrazole group exhibits good film formability and flexibility. In particular, an explosive thermal degradation of the PVT with high tetrazole content is observed at 262 °C.