Free Radical Solution Copolymerization of Acidic Ionic Liquid Monomer 1‐Vinyl‐3‐Carboxyethylimidazolium Bromide With Acrylonitrile

Acidic ionic liquid monomer 1‐vinyl‐3‐carboxyethylimidazolium bromide (ViCEI + Br − ) was used to copolymerize with acrylonitrile (AN) for the first time, and the copolymers with high molecular weights were obtained successfully by using azobisisobutyronitrile as the initiator and dimethylsulfoxide as the solvent. The copolymers were characterized by 1 H‐NMR, XRD, thermogravimetric analysis (TGA) and x‐ray diffraction (XRD). Based on the kinetic data of the above copolymerization, the reactivity ratios of acrylonitrile (r AN ) and ViCEI + Br − (r ViCEI + Br − ) were calculated by the Kelen‐Tüdos method, which are 2.44 and 1.75 respectively. The XRD results show that when the temperature is higher than 260°C, the crystal structure of the copolymer crystalline region gradually disappears with the progress of the reaction. The TGA results show that ViCEI + Br − can improve the thermal stability and char yields of PAN copolymer, which can be used as a potential precursor for the PAN‐based carbon fiber.