Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, SP, Brazil.
Carbohydr Polym. 2019 Feb 1;205:524-532. doi: 10.1016/j.carbpol.2018.10.055. Epub 2018 Oct 29.
We synthesized a series of quaternary ammonium acetates (QAAcOs) and assessed their solutions in DMSO as cellulose solvents. NAcO/DMSO did not dissolve cellulose; substitution of its methyl groups resulted in efficient cellulose solvents; NAcO/DMSO dissolved cellulose with difficulty. We attribute the inefficiency of both QAAcOs to: strong anion-cation interactions, NAcO; steric effects and cation-cation hydrophobic interactions, NAcO. Using isothermal titration calorimetry, we determined the enthalpies (H) of QAAcO (endothermic) dissolution, and QAAcO/cellobiose (exothermic) interactions; both in dimethyl sulfoxide/acetonitrile. The ratios of H are 5.34:1:1.45, for NAcO, NAcO, and NAcO, respectively, i.e., dissolution of the first and third QAAcO in the solvent requires more energy. The corresponding ratios for QAAcO interaction with cellobiose are: 0.74:1:0.79, i.e., the second QAAcO interacts more strongly with cellobiose. This order of solvent efficiency is corroborated by SEM images of regenerated cotton linters. Light scattering showed that dissolved cellulose can be regenerated as nanoparticles by dialysis.
我们合成了一系列季铵乙酸盐（QAAcO），并评估了它们在 DMSO 中的溶液作为纤维素溶剂的性能。NAcO/DMSO 不能溶解纤维素；取代其甲基基团可得到有效的纤维素溶剂；NAcO/DMSO 难以溶解纤维素。我们将 QAAcO 的低效归因于：强阴离子-阳离子相互作用，NAcO；空间位阻和阳离子-阳离子疏水性相互作用，NAcO。使用等温滴定量热法，我们测定了 QAAcO（吸热）溶解和 QAAcO/纤维二糖（放热）相互作用的焓（H）；均在二甲亚砜/乙腈中进行。H 的比值分别为 5.34:1:1.45，对于 NAcO、NAcO 和 NAcO，即第一和第三 QAAcO 在溶剂中的溶解需要更多的能量。与纤维二糖相互作用的 QAAcO 的相应比值为：0.74:1:0.79，即第二 QAAcO 与纤维二糖的相互作用更强。这一溶剂效率的顺序得到了再生棉绒的 SEM 图像的证实。光散射表明，溶解的纤维素可以通过透析再生为纳米颗粒。
