Ma Lan, Wang Ge, Sun Shengtong, Wu Peiyi
State Key Laboratory of Molecular Engineering of Polymers, Collaborative Innovation Center of Polymers and Polymer Composite Materials, Department of Macromolecular Science, and Laboratory of Advanced Materials, Fudan University, Shanghai 200433, China.
Phys Chem Chem Phys. 2017 Aug 23;19(33):22263-22271. doi: 10.1039/c7cp03602g.
The study of a ternary solution involving a thermoresponsive polymer, a thermoresponsive ionic liquid (IL), and a solvent will not only help with interpreting their distinct phase transition behavior, but also promote the development of novel thermoresponsive systems. In this paper, we investigate the influence of a conventional thermoresponsive polymer, poly(2-isopropyl-2-oxazoline) (PIPOZ), on the phase transition behavior of two thermoresponsive ILs ([P][MC3S], [P][SS]) with different structures. Although the addition of PIPOZ reduces the transition temperatures of both ILs, our analyses demonstrate that there exists a large difference in the microdynamic phase transition mechanisms between [P][MC3S]/PIPOZ and [P][SS]/PIPOZ aqueous solutions. Both PIPOZ and [P][MC3S] experience unexpectedly an unusual over-hydration process before a two-step phase transition of the mixture solution, which can be explained by the presence of a new kind of intermolecular bridging hydrogen bond (IL-water-polymer), whereas only PIPOZ undergoes dehydration around the transition temperature of the [P][SS]/PIPOZ aqueous solution. Further spectral analyses reveal that both [P][MC3S] and PIPOZ engage in the phase separation of the ternary solution jointly, whereas PIPOZ takes part in the phase transition of [P][SS]/PIPOZ solution more independently.
对包含热响应性聚合物、热响应性离子液体（IL）和溶剂的三元溶液进行研究，不仅有助于解释它们独特的相变行为，还能促进新型热响应系统的发展。在本文中，我们研究了传统热响应性聚合物聚（2-异丙基-2-恶唑啉）（PIPOZ）对两种结构不同的热响应性离子液体（[P][MC3S]、[P][SS]）相变行为的影响。尽管添加PIPOZ降低了两种离子液体的转变温度，但我们的分析表明，[P][MC3S]/PIPOZ和[P][SS]/PIPOZ水溶液的微观动力学相变机制存在很大差异。在混合溶液发生两步相变之前，PIPOZ和[P][MC3S]都意外地经历了一个不寻常的过度水合过程，这可以用一种新型分子间桥连氢键（离子液体-水-聚合物）的存在来解释，而在[P][SS]/PIPOZ水溶液的转变温度附近，只有PIPOZ发生脱水。进一步的光谱分析表明，[P][MC3S]和PIPOZ都共同参与了三元溶液的相分离，而PIPOZ在[P][SS]/PIPOZ溶液的相变中参与得更为独立。
