Ostlund Asa, Lundberg Dan, Nordstierna Lars, Holmberg Krister, Nydén Magnus
Department of Chemical and Biological Engineering, Applied Surface Chemistry, Chalmers University of Technology, SE-412 96 Goteborg, Sweden.
Biomacromolecules. 2009 Sep 14;10(9):2401-7. doi: 10.1021/bm900667q.
Solutions of cellulose in a mixture of tetrabutylammonium fluoride and dimethyl sulfoxide (TBAF/DMSO) containing small and varying amounts of water were studied by nuclear magnetic resonance (NMR). By measuring the composition dependences of (19)F NMR and (1)H NMR chemical shifts and line widths, details on the dissolution and gelation mechanisms for cellulose in TBAF/DMSO were elucidated. Our results suggest that the strongly electronegative fluoride ions act as hydrogen bond acceptors to cellulose hydroxyl groups, thus dissolving the polymer by breaking the cellulose-cellulose hydrogen bonds and by rendering the chains an effective negative charge. It was found that the fluoride ions also interact strongly with water. Small amounts of water remove the fluoride ions from the cellulose chains and allow reformation of the cellulose-cellulose hydrogen bonds, which leads to formation of highly viscous solutions or gels even at low cellulose concentrations.
通过核磁共振（NMR）研究了纤维素在含有少量且变化量水的四丁基氟化铵与二甲基亚砜混合物（TBAF/DMSO）中的溶液。通过测量¹⁹F NMR和¹H NMR化学位移及线宽对组成的依赖性，阐明了纤维素在TBAF/DMSO中的溶解和凝胶化机制的细节。我们的结果表明，强电负性的氟离子作为纤维素羟基的氢键受体，通过破坏纤维素 - 纤维素氢键并使链带有有效负电荷来溶解聚合物。发现氟离子也与水强烈相互作用。少量的水会将氟离子从纤维素链上除去，并使纤维素 - 纤维素氢键重新形成，这导致即使在低纤维素浓度下也会形成高粘性溶液或凝胶。
