College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, China.
Phys Chem Chem Phys. 2018 May 23;20(20):14223-14233. doi: 10.1039/c8cp01268g.
The physical dissolution of cellulose in aqueous solutions of tetramethyl ammonium hydroxide, triethylmethyl ammonium hydroxide, tetraethyl ammonium hydroxide, benzyltrimethyl ammonium hydroxide, benzyltriethyl ammonium hydroxide, NaOH and LiOH via freezing-thawing was investigated. Increasing the hydrophobicity of the cation greatly improved its dissolution capacity, leading to significant enhancement of cellulose solubility and stability against chain aggregation and gelation. The hydrophobic cations accumulated at the cellulose interface and decreased the surface tension, favouring dispersion of the disintegrated cellulose due to its amphiphilicity; this was consistent with molecular dynamics simulations. On the other hand, the solubility of cellulose followed the Hofmeister series, and cations with greater kosmotropicity originating from their greater hydrophobicity exhibited stronger dissolution power; this observed interaction pattern may be useful for further exploration and designation of novel solvents of cellulose. These aqueous quaternary ammonium hydroxides can be readily recycled and reused, which presents great potential in the green chemistry field.
通过冷冻-解冻的方法,研究了在四甲基氢氧化铵、三乙基甲基氢氧化铵、四乙基氢氧化铵、苄基三甲基氢氧化铵、苄基三乙基氢氧化铵、氢氧化钠和氢氧化锂的水溶液中,纤维素的物理溶解情况。阳离子的疏水性的增加极大地提高了其溶解能力,从而显著提高了纤维素的溶解度,并增强了其对链聚集和凝胶化的稳定性。疏水阳离子在纤维素界面上聚集,降低了表面张力,有利于分散由于其两亲性而分散的分解纤维素;这与分子动力学模拟一致。另一方面,纤维素的溶解度遵循豪夫迈斯特序列,并且疏水性更大的具有更大等渗性的阳离子表现出更强的溶解能力;这种观察到的相互作用模式可能有助于进一步探索和设计纤维素的新型溶剂。这些水相季铵羟化物可以很容易地回收和再利用,这在绿色化学领域具有很大的潜力。