Dissolving limitations: The power of DMSO activation for cellulose SEC analysis

The molar mass distribution is a crucial parameter for cellulose samples used in both research and industry, typically determined by size-exclusion chromatography (SEC) coupled with multi-angle laser light scattering and refractive index detection (MALLS-RI). While DMSO activation has been proven effective for dissolving challenging samples, such as regenerated fibers, in 9 % (w/v) DMAc/LiCl, the structural changes occurring during this activation are not yet fully understood. To address this, we analysed the effects of the DMSO activation on man-made fibers (Lyocell, Viscose, Modal) and microcrystalline cellulose over varying durations (30 min, 1 d, and 7 d), compared to conventional activation with DMAc for 7 d. The DMSO activation did not only influence the crystallinity index and hemicellulose content but also altered the dissolution behavior of regenerated cellulose fibers. Moreover, the DMSO activation step facilitated the dissolution of low-molar-mass fractions in 0.9 % (w/v) DMAc/LiCl. Importantly, the DMSO activation protocol was optimized to prevent the potential loss of low-molar-mass fractions for hemicellulose-rich samples. The altered (dn/dc)_μ value was determined and applied to ensure accurate data analysis.