Effect of Cotton Activation and Solvent Evaporation on the Production of Regenerated Cellulose Membranes Using Lithium Chloride/ <i>N</i> , <i>N</i> -Dimethylacetamide

Cellulose is a renewable biopolymer with great potential for sustainable applications, but its high crystallinity hinders dissolution in conventional solvents. Regenerated cellulose membranes were developed from commercial cotton using the lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) system. Different activation strategies (DMAc and DMAc/KMnO4) and DMAc evaporation times (48 and 72 h) before regeneration were evaluated. The activations did not alter the chemical structure of the cotton fibers but promoted greater dissolution efficiency, especially with KMnO4, without significantly affecting crystallinity. However, the degree of polymerization decreased from 2475 DP in the raw material to approximately 880 DP in the membranes obtained from both activated samples. Extending the DMAc evaporation time from 48 to 72 h improved microstructural homogeneity and increased the maximum degradation temperature by up to 44 °C. Structural analyses confirmed the transformation of native cellulose I into a predominantly amorphous regenerated structure with minor contributions of cellulose II. The results demonstrate that the combined control of cellulose activation and solvent evaporation is an effective strategy to tailor the structural and physicochemical properties of regenerated cellulose membranes, enabling their potential use in polymer-based filtration and separation applications.