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Towards Biomimicking Wood: Fabricated Free-standing Films of Nanocellulose, Lignin, and a Synthetic Polycation
Published on: June 17, 2014
Opposing solubility of cellulose and starch in [Emim][OAc]-water mixtures: A microstructure and energetic perspective
Jiale Xu1, Haiyun Hou1, Tiantian Ma1
1Xi'an Key Laboratory of Textile Chemical Engineering Auxiliaries, College of Environmental and Chemical Engineering, Key Laboratory of Functional Textile Materials and Products, Ministry of Education, Xi'an Polytechnic University, Xi'an, Shaanxi, 710048, China.
Abstract:
Ionic liquid 1-ethyl-3-methylimidazole acetate ([Emim][OAc] or IL) is a sustainable cellulose/starch solvent, while water acts an anti-solvent for their dissolution in [Emim][OAc]. Our previous work has indicated that mixtures with molar fraction x ≈ 0.3-0.5 of [Emim][OAc] in [Emim][OAc]-water mixtures lead to cellulose regeneration but the highest starch solubility. To elucidate the origin of these opposite effects further, this work employs physicochemical and 1H NMR analyses, COSMO-RS predictions, and MD simulations, along with solubility data. We focus on the liquid microstructure, molecular interactions, and energetic characteristics of the mixtures and their correlation with cellulose and starch solubility. Our results reveal that stronger anion-water interactions lower the energy state of the IL anion, while weaker cation-water interactions elevate that of the IL cation, resembling an activated cation and a deactivated anion. This effect peaks around x ≈ 0.3-0.5, forming a unique hydrogen-bonded network with highly activated cations and water molecules along with stabilized anions. This microstructure explains both cellulose regeneration and maximum starch solubility in this composition range. These findings advance the understanding of how water regenerates cellulose while enhancing starch dissolution at special IL:water compositions, providing guidance for designing efficient, eco-friendly, recyclable solvents for separating cellulose-starch blends.
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