Poly(acrylonitrile‐methyl acrylate‐3‐ammonium carboxylate‐3‐butenoic acid methyl ester) as a Potential Carbon Fiber Precursor with an Expedient Stabilization Effect and Spinnability

To enhance the comprehensive properties of carbon fiber precursors, 3‐ammonium carboxylate‐3‐butenoic acid methyl ester (ACBM) as a raw material polymerized with acrylonitrile (AN) and methyl acrylate (MA) via radical solution polymerization, resulting in P(AN‐MA‐ACBM) as a terpolymer. The ester side groups of the ACBM monomer reduced the binding energy of the acrylonitrile copolymer, thereby improving spinnability and oxygen permeability during the stabilization process. Additionally, the ammonium carboxylate groups (─COO − NH 4 + ) in ACBM initiated nucleophilic assault on the C adjacent cyano group, effectively lowering the initial cyclization temperature of polyacrylonitrile (PAN). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) systematically revealed the stability mechanism. X‐ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) results proved the polymer structure. The ACBM monomer significantly reduced the initial temperature and activation energy ( E a ), broadened the exothermic peak, and improved the polymer's stability. P(AN‐MA‐ACBM) as a precursor demonstrated superior potential to produce high‐performance carbon fibers compared with the binary acrylonitrile‐methyl acrylate [P(AN‐co‐MA)] copolymer. Rheological analysis further confirmed that P(AN‐MA‐ACBM) exhibited superior spinnability to P(AN‐co‐MA). This study provides theoretical support for advancing the spinning process for carbon fiber production.