Zhang Shaohua, Li Na, Zheng Liqiang, Li Xinwei, Gao Yanan, Yu Li
Key Laboratory of Colloid and Interface Chemistry, Shandong University, Ministry of Education, Jinan, P. R. China.
J Phys Chem B. 2008 Aug 21;112(33):10228-33. doi: 10.1021/jp8035132. Epub 2008 Jul 26.
Three amphiphilic poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) ethers triblock copolymers, denoted Pluronic L61 (PEO3PPO30PEO3), Pluronic L64 (PEO13PPO30PEO13), and Pluronic F68 (PEO79PPO30PEO79) were shown to aggregate and form micelles in ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4) and 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6). The surface tension measurements revealed that the dissolution of the copolymers in ILs depressed the surface tension in a manner analogous to aqueous solutions. The cmcs of three triblock copolymers increase following the order of L61, L64, F68, suggesting that micellar formation was driven by solvatophobic effect. cmc and gamma cmc decrease with increasing temperature because hydrogen bonds between ILs and hydrophilic group of copolymers decrease and accordingly enhance the solvatophobic interaction. Micellar droplets of irregular shape with average size of 50 nm were observed. The thermodynamic parameters DeltaGm0, DeltaHm0, DeltaSm0 of the micellization of block copolymers in bmimBF4 and bmimPF6 were also calculated. It was revealed that the micellization is a process of entropy driving, which was further confirmed by isothermal titration calorimetry (ITC) measurements.
三种两亲性聚（氧乙烯）-聚（氧丙烯）-聚（氧乙烯）醚三嵌段共聚物，分别为普朗尼克L61（PEO3PPO30PEO3）、普朗尼克L64（PEO13PPO30PEO13）和普朗尼克F68（PEO79PPO30PEO79），已证实在离子液体（ILs）1-丁基-3-甲基咪唑四氟硼酸盐（bmimBF4）和1-丁基-3-甲基咪唑六氟磷酸盐（bmimPF6）中会聚集并形成胶束。表面张力测量结果表明，共聚物在离子液体中的溶解会以类似于水溶液的方式降低表面张力。三种三嵌段共聚物的临界胶束浓度（cmc）按照L61、L64、F68的顺序增加，这表明胶束形成是由疏溶剂效应驱动的。cmc和临界胶束浓度下的表面张力（gamma cmc）随温度升高而降低，因为离子液体与共聚物亲水基团之间的氢键减少，从而增强了疏溶剂相互作用。观察到平均尺寸为50 nm的不规则形状的胶束液滴。还计算了嵌段共聚物在bmimBF4和bmimPF6中胶束化的热力学参数ΔGm0、ΔHm0、ΔSm0。结果表明，胶束化是一个熵驱动的过程，等温滴定量热法（ITC）测量进一步证实了这一点。
