Synthesis of Poly(acrylonitrile-<i>co</i>-acrylic acid) for High-Strength Carbon Nanofibers

Electrospun polyacrylonitrile (PAN) nanofibers are widely recognized as precursors for fabricating carbon nanofibers (CNFs), yet the limited degree of cyclization and frequent fiber breakages during stabilization hinder the mechanical performance of the resulting CNFs. This study introduces a strategy to overcome these challenges by synthesizing poly(acrylonitrile-co-acrylic acid) copolymers with controlled acrylic acid ratios. The incorporation of uniformly distributed carboxyl groups in acrylic acid units within the polymer structure enabled an ionic cyclization pathway, reducing the maximum cyclization temperature to 250 °C and achieving a cyclization degree exceeding 82%. This enhanced stabilization process yielded CNFs with highly graphitized structures with an IG/ID ratio of 3.0 and minimal fiber breakages of less than 0.1%. Notably, CNFs derived from P(AN-AA)-5% exhibited a remarkable tensile strength of 28.2 MPa, over three times greater than that of conventional PAN-derived CNFs of 8.8 MPa. This innovative approach highlights the potential of copolymer-based modifications to advance CNF fabrication, offering a pathway for improved mechanical properties and expanded application prospects.