Structural features of undrawn poly(acrylonitrile) gel fibers: The relationship between multilevel structures and activation energy of the cyclization reaction

Poly(acrylonitrile) (PAN) fibers are essential precursors for carbon fiber production. This study examined the hierarchical structure of undrawn PAN gel fibers prepared in coagulation baths with varying methanol concentrations using multiple scattering techniques (XRD, SAXS, USAXS, and SANS). By avoiding the drawing process, the effects of gel-spinning conditions on fiber structure were isolated. At high methanol concentrations, corresponding to temperatures well below the melting point of the gel solvent, the macromolecular cluster size ( R gg ) remained nearly unchanged with increasing immersion time. However, crystallinity increased while the average crystallite size decreased, even when the gel solvent was frozen. Additionally, R gg showed a correlation with the activation energy ( E a ) for the PAN cyclization reaction, as measured by differential scanning calorimetry (DSC). These findings suggest that controlling chain mobility and molecular clustering during the gel-spinning process may be a promising strategy to optimize structural properties and reduce energy consumption in carbon fiber manufacturing. • ●Coagulation bath temperature affects macromolecular clustering in PAN gel fibers. • ●Lower temperatures yield rigid clusters; higher temperatures lead to looser structures. • ●Looser clusters correlate with lower Ea for PAN cyclization, enabling energy saving. • ●Controlling cluster structure may help reduce energy use in carbon fiber production. • ●Simultaneous drawing and cyclization is proposed to further save processing energy.