(396b) Dissolution of Semicrystalline Polymers: Effects of Solvent Diffusion, Polymer Chain Decrystallization and Disentanglement, and Particle Size

A phenomenological model is presented that captures the phenomena governing the dissolution of semicrystalline polymers, e.g., solvent diffusion, transformation from crystalline to amorphous domains, specimen swelling, and polymer chain untangling. The model is validated for the case of cellulose fiber swelling and dissolution in an ionic liquid. A parametric sensitivity analysis is carried out to assess the impact of decrystallization rate constant, disentanglement rate, concentration dependence of solvent diffusivity, disentanglement threshold, and thickness of external boundary layer on the swelling and dissolution of semicrystalline polymer fibers. [Ghasemi, M.; Singapati, A. Y.; Tsianou, M.; Alexandridis, P., Dissolution of semicrystalline polymer fibers: numerical modeling and parametric analysis. AIChE Journal 2017, 63 (4), 1368-1383. DOI: 10.1002/aic.15615] Whereas fibers with lower crystallinity swell more and faster, the degree of crystallinity does not affect the dissolution rate. Fibers of smaller diameter swell more and become amorphous faster. When decrystallization is important, the solubility of thinner fibers increases more with a reduction in the crystallinity compared to the diameter. However, when the dissolution is controlled by polymer chain disentanglement, or in the case of dissolution of fibers having larger diameters, a reduction in the particle size could boost dissolution. [Ghasemi, M.; Alexandridis, P.; Tsianou, M., Dissolution of cellulosic fibers: effect of crystallinity and fiber diameter. Biomacromolecules 2018, 19 (2), 640-651. DOI: 10.1021/acs.biomac.7b01745] The insights obtained from this study would facilitate the design of efficient solvent systems and processing conditions for the dissolution of semicrystalline polymers such as cellulose, polyglycolic acid, and polyesters.