Role of low-concentration acetic acid in promoting cellulose dissolution

In this study, we report on a new strategy using low-concentration acetic acid (LCAA) to promote cellulose dissolution. High-molecular-weight (HMW) cotton cellulose (DP > 5000) was simply soaked in a dilute acetic acid aqueous solution (1 vol%) prior to dissolution. Using N,N-dimethylacetamide/lithium chloride as the solvent system, the dissolution of LCAA-activated cellulose was significantly improved. Material characterization results indicated that no cellulose acetylation occurred during the dissolution process and the acetic acid could be easily removed during cellulose regeneration. It was also noticed that using LCAA to activate cellulose significantly reduced the viscosity of cellulose solution and promoted the dissolution of HMW cellulose. The crystallinity of LCAA-activated cellulose was not impacted, and the molecular weight of LCAA-activated cellulose was not significantly decreased as compared to cellulose without LCAA activation. The LCAA in cellulose played a pivotal role, by enhancing the solvation of the lithium cation. As a result, the initial free chloride concentration was able to increase and interact with inter and intra molecular hydrogen bonds of cellulose. Understanding the role of LCAA in the dissolution of cellulose is of particular interest in developing a new concept to design new solvents and effective strategies for cellulose dissolution.