ABSTRACT This study investigates the microscale dual‐diffusion process of polyacrylonitrile (PAN) solutions in the coagulation bath and the process of PAN fiber formation. The interaction peaks assignment between solvent and water were identified by analyzing the Fourier transform infrared spectroscopy (FTIR) characteristic peaks of red or blue shift. The time‐resolved attenuated total reflection FTIR technique was employed to analyze the dual‐diffusion process. Enabling quantitative determination of diffusion coefficients based on Fick's second law. A correlation was established between diffusion coefficients, the microstructural characteristics of PAN membranes and the cross‐sectional morphology of PAN nascent fibers. Additionally, examination of the microstructure of triple times stretched PAN nascent fibers revealed the formation mechanism of fibers with “Fibrils Within a Filament”.
Li et al. (2026) studied this question.