Researching the Mechanism Underlying the Low Cellulose Pretreatment Efficiency at High DMSO/Ionic Liquid Ratios

High DMSO/[Amim]Cl ratios impair cellulose pretreatment efficiency. In DMSO/[Amim]Cl systems (0–60 wt% DMSO), cellulose solubility and saccharification rates declined gradually (0–50 wt%) then sharply (50–60 wt%). Structural changes intensified at 50–60 wt% DMSO, with greater decrystallization (20.93% vs 2.85%) and hydrophobicity (23.08° vs 1.86°) reductions. SEM revealed denser, smoother surfaces at 60 wt% DMSO, reducing accessibility. Kamlet-Taft analysis showed nonlinear decreases in hydrogen bond acidity/basicity (α/β: 0.59/1.25 → 0.24/0.73), suggesting weakened hydrogen bond disruption at 60 wt% DMSO, lowering pretreatment efficiency.