Departamento de Química, CICECO, Universidade de Aveiro, 3810-193 Aveiro, Portugal.
Chemistry. 2012 Feb 6;18(6):1831-9. doi: 10.1002/chem.201101780. Epub 2012 Jan 3.
New polyethylene glycol (PEG)/ionic liquid aqueous biphasic systems (ABS) are presented. Distinct pairs of PEG polymers and ionic liquids can induce phase separation in aqueous media when dissolved at appropriate concentrations. Phase diagrams have been determined for a large array of systems at 298, 308 and 323 K. A comparison of the binodal curves allowed the analysis of the tunable structural features of the ionic liquid (i.e., anionic nature, cationic core, cationic alkyl side chain length and functionalisation, and number of alkyl substituents in the cation) and the influence of the molecular weight of the PEG polymer on the ability of these solutes to induce an ABS. It was observed that contrary to typical ABS based on ionic liquids and inorganic salts, in which the phase behaviour is dominated by the formation of the hydration complexes of the ions, the interactions between the PEG polymers and ionic liquids control the phase demixing in the polymer-type ABS studied herein. It is shown that both the ionic liquids and PEG polymers can act as the salting-out species; that is, it is an occurrence that is dependent on the structural features of the ionic liquid. For the first time, PEG/ionic liquid ABS are reported and insight into the major interactions that govern the polymer/ionic liquid phase behaviour in aqueous media are provided. The use of two different nonvolatile and tunable species (i.e., ionic liquids and PEG polymers) to form ABS allows the polarities of the phases to be tailored. Hence, the development of environmentally friendly separation processes that make use of these novel systems is envisaged.
介绍了新的聚乙二醇（PEG）/离子液体双水相体系（ABS）。当适当浓度溶解时，不同的 PEG 聚合物和离子液体对可以在水介质中诱导相分离。在 298、308 和 323 K 下，已经确定了大量系统的相图。比较双节点曲线允许分析离子液体的可调结构特征（即阴离子性质、阳离子核心、阳离子烷基侧链长度和官能化以及阳离子中的烷基取代基数量）以及 PEG 聚合物的分子量对这些溶质诱导 ABS 的能力的影响。观察到，与基于离子液体和无机盐的典型 ABS 相反，在这些 ABS 中，相行为主要由离子的水合络合物的形成决定，PEG 聚合物和离子液体之间的相互作用控制了所研究的聚合物型 ABS 中的相分离。结果表明，离子液体和 PEG 聚合物都可以作为盐析剂；也就是说，这是一种依赖于离子液体结构特征的现象。首次报道了 PEG/离子液体 ABS，并提供了有关控制离子液体在水介质中与聚合物相互作用的主要相互作用的见解。使用两种不同的非挥发性和可调谐物质（即离子液体和 PEG 聚合物）形成 ABS 可以调整相的极性。因此，预计将开发利用这些新型系统的环保分离工艺。
