Role of Small Amounts of Water in the Gelation of Polyacrylonitrile Solutions in Dimethyl Sulfoxide: Rheology, Kinetics, and Mechanism

We studied the effect of water addition on the gelation kinetics of polyacrylonitrile (PAN) in dimethyl sulfoxide (DMSO) solutions. The gelation process was considered an evolution of the rheological properties, which were associated with a change in the PAN–DMSO–water system interactions. This approach enabled a detailed investigation of gelation kinetics and phase transformations across varying temperatures, identifying regions associated with solutions, dispersions, thermoreversible, and thermo-irreversible gels. The gelation temperatures of the ternary systems were ascertained using the Winter method. A pivotal element in the gelation process of PAN solutions was identified: the ratio of the unassociated solvent concentration available for PAN solvation relative to the PAN concentration. This specific ratio is instrumental in dictating the formation of nitrile–nitrile interactions. The obtained results will contribute to the understanding of physicochemical approaches to optimizing the composition of gelling polymer solutions in technologies, giving new knowledge to the fields of polymer and materials science.