PAN chemical modification: Synthesis and characterization of terpolymers with 1,2,4-oxadiazolic pendant groups

The terpolymers containing oxadiazole pendant groups, obtained from chemical modification of a commercial polymer, present great interest due to their novelty and possible interesting properties. The synthesis of amidoxime-nitrile-3-hydroxyphenyl-1,2,4-oxadiazole (ANHOT) of different conversion times was prepared by chemical modification of polyacrylonitrile (PAN) as starting material. The first step of ANHOT synthesis was the well-known nitrile conversion into amidoxime groups. Afterwards, the 3,5-disubstituted 1,2,4-oxadiazolic ring was obtained by treatment of amidoxime-groups with an acyl chloride. The molecular structures were confirmed by IR, UV-Vis, 13C and 1H NMR spectroscopies. Conversion yields were calculated from elemental analysis. Thermal properties were studied by DSC and TGA techniques. All ANHOT series are completely soluble in very polar solvents. The dependency of viscosity with the conversion degree was analyzed with a control rate (CR) viscosimeter. Viscoelastic behavior was analyzed by rheometric measurements. The highest viscosity and elastic behavior were obtained with ANHOT of an hour conversion time; in this way it is the most attractive polymer among the ANHOT series.