Inoue Tohru, Misono Takeshi
Department of Chemistry, Faculty of Science, Fukuoka University, Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan.
J Colloid Interface Sci. 2009 Sep 1;337(1):247-53. doi: 10.1016/j.jcis.2009.05.002. Epub 2009 May 12.
Cloud point temperatures, T(c), of polyoxyethylene (POE)-type nonionic surfactants in a room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF(6)), were measured and compared with those previously obtained for the surfactant solution in bmimBF(4). The T(c)s for bmimPF(6) solution are higher than those for bmimBF(4) solution by approx. 40 degrees C. This means that the surfactant molecules are more solvophilic in bmimPF(6) compared to bmimBF(4). The analysis of (1)H NMR chemical shift measurements proved that the higher solvophilicity of the surfactants in bmimPF(6) is attributed to weaker hydrogen-bond interaction between bmim cation and PF6- anion than that between bmim cation and BF4- anion. This interpretation is consistent with the interaction energy parameters derived from the thermodynamic analysis of cloud point curve applying the Flory-Huggins model for phase separation in polymer solution. The present work demonstrates that the property of imidazolium-based ionic liquids as a solvent is determined by a balance of interactions among imidazolium cation, counter anion, and solute molecule.
测量了聚氧乙烯（POE）型非离子表面活性剂在室温离子液体1-丁基-3-甲基咪唑六氟磷酸盐（bmimPF₆）中的浊点温度T(c)，并与之前在bmimBF₄中获得的表面活性剂溶液的浊点温度进行了比较。bmimPF₆溶液的T(c)比bmimBF₄溶液的T(c)高约40℃。这意味着与bmimBF₄相比，表面活性剂分子在bmimPF₆中具有更强的亲溶剂性。¹H NMR化学位移测量分析表明，表面活性剂在bmimPF₆中较高的亲溶剂性归因于bmim阳离子与PF₆⁻阴离子之间的氢键相互作用比bmim阳离子与BF₄⁻阴离子之间的氢键相互作用弱。这种解释与应用聚合物溶液相分离的Flory-Huggins模型对浊点曲线进行热力学分析得出的相互作用能参数一致。目前的工作表明，咪唑基离子液体作为溶剂的性质是由咪唑阳离子、抗衡阴离子和溶质分子之间相互作用的平衡决定的。
