Hydrogen bond producers in powerful protic ionic liquids for enhancing dissolution of natural cellulose

The manipulation of hydrogen bonding within protic ionic liquids is conducive to conquering the robust hydrogen bonding interactions in cellulose for its effective dissolution, but it is a great challenge to establish the delicate balance of hydrogen bonding network between solvent and cellulose. Herein, we proposed the concept of “hydrogen bond producers” for urea molecules in 1,1,3,3-tetramethylguanidinium methoxyacetate acid ([TMGH][MAA]) to enhance the dissolution of cellulose. The optimization of physicochemical properties for [TMGH][MAA] solvent as a function of urea concentration revealed a remarkable increase in cellulose solubility from 13% to 17% (w/w) by adding only 0.25 wt% urea, highlighting the efficiency of [TMGH][MAA] as a powerful solvent for the dissolution of cellulose. The experimental and simulation results verified that the significant improvement on dissolution of cellulose was attributed to the hydrogen bonding interaction of urea molecules with ion pairs and part of free ions, reducing the interference with the active ions bonded to cellulose. Furthermore, the considerable enhancement on comprehensive properties of regenerated cellulose films demonstrated the effectiveness of [TMGH][MAA]/urea solvent. The concept of “hydrogen bond producers” presented here opens a new avenue for significantly enhancing the dissolution of natural cellulose, promoting the sustainable development in large-scale processing of cellulose.