Terpolymers of acrylonitrile, methyl acrylate, and 2‐acrylamido‐2‐methylpropane sulfonic acid for carbon fiber precursor: Effect of comonomers on the thermal stabilization of polyacrylonitrile copolymers

Abstract Polyacrylonitrile (PAN) copolymers are important precursors for the preparation of high‐performance PAN‐based carbon fibers. In this study, different ratios of P(AN‐co‐AMPS) and P(AN‐co‐MA‐co‐AMPS) were prepared by solution polymerization. The compositional structure, thermal, and crystallization properties of P(AN‐co‐AMPS) and P(AN‐co‐MA‐co‐AMPS) were characterized. The results show that an increase in the AMPS feeding ratio is beneficial for improving the thermal stability and crystallization ability of the PAN copolymer; however, it also reduces the molecular weight of the copolymer and increases the cyclization exothermic peak temperature, which is not conducive to the preparation of high‐performance carbon fibers. This problem is avoided in P(AN‐co‐MA‐co‐AMPS), which maintains its high thermal stability and crystallization properties when appropriate amounts of MA and AMPS are introduced, and P(AN‐co‐MA‐co‐AMPS) has smoother cyclization exothermic rates, lower onset exothermic temperatures and lower peak exothermic temperatures. The structural changes of PAN, P(AN‐co‐MA), and P(AN‐co‐MA‐co‐AMPS) during thermal stabilization were investigated in detail using Fourier‐transform infrared spectroscopy and it was found that P(AN‐co‐MA‐co‐AMPS) formed more stable structures at lower temperatures. Furthermore, when the AN:MA:AMPS mass ratio is 97.5:1.5:1, P(AN‐co‐MA‐co‐AMPS) has the best overall performance. Our results suggest that the P(AN‐co‐MA‐co‐AMPS) has potential as a precursor for carbon fibers.