二维相关红外光谱法表征2-O-甲基纤维素在离子液体Amim-Cl和Amim-(MeO)PHO_(2)中的溶解机理

Characterization of the Dissolution Mechanism of 2-O-Methylcellulose in Amim-Cl and Amim-(MeO)PHO_(2) Ionic Liquids by Two-Dimensional Correlation Infrared Spectroscopy

以微晶纤维素为原料合成了定向取代的2-O-甲基纤维素并制备了2种离子液体(Amim-Cl和Amim-(MeO)PHO_(2)),对2-O-甲基纤维素及其溶于离子液体Amim-Cl和Amim-(MeO)PHO_(2)的溶液进行了二维相关红外表征。通过分析2-O-甲基纤维素的氢键特征峰,揭示了不同羟基在其溶于离子液体过程中发挥的作用。研究结果表明,相较于纤维素,2-O-甲基纤维素中无2-OH…O-6氢键,仍存有分子内氢键3-OH…O-5和分子间氢键6-OH…O′-3。在2-O-甲基纤维素溶于离子液体的过程中,离子液体主要破坏的是分子间氢键6-OH…O′-3,而分子内氢键3-OH…O-5不受影响。离子液体的阴阳离子在溶解2-O-甲基纤维素的过程中均发挥了重要作用,与2-O-甲基纤维素6位羟基相互作用形成新的氢键是2-O-甲基纤维素溶于离子液体的主要动力。

2-O-methyl cellulose was synthesized from microcrystalline cellulose and two kinds of ionic liquids were prepared,then 2-O-methyl cellulose and its solution dissolved in Amim-Cl and Amim-(MeO)PHO_(2) ionic liquids were characterized by two-dimensional correlation infrared spectroscopy(IR).The characteristic peaks of hydrogen bonds of 2-O-methyl cellulose were analyzed,revealing the roles of different hydroxyl groups in the process of dissolving in ionic liquids.The results show that,compared to cellulose,2-O-methyl cellulose no longer has 2-OH…O-6 hydrogen bonds,but there are still 3-OH…O-5 intramolecular hydrogen bonds and 6-OH…O-3 intermolecular hydrogen bonds.In the process of dissolving 2-O-methyl cellulose in ionic liquids,ionic liquids mainly destroy 6-OH…O-3 intermolecular hydrogen bonds,while 3-OH…O-5 intramolecular hydrogen bonds are not affected.Both anions and cations of ionic liquids play an important role in the process of dissolving 2-O-methylcellulose.They interact with the hydroxyl group at the 6-position of 2-O-methylcellulose to form a new hydrogen bond,which is the main driving force for the dissolution of 2-O-methylcellulose in ionic liquids.