Lower Critical Solution Temperature Phase Behavior of Poly(n-butyl methacrylate) in Ionic Liquid Mixtures
Lower Critical Solution Temperature Phase Behavior of Poly(n-butyl methacrylate) in Ionic Liquid Mixtures
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DOI：
10.1021/ma401450w
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发表时间：
2013-12-10
期刊：
影响因子：
5.5
通讯作者：
Lodge, Timothy P.
中科院分区：
文献类型：
--
作者：
Hoarfrost, Megan L.;He, Yanpu;Lodge, Timothy P.
离子液体的特性组合使其成为聚合物的有趣溶剂，但关于聚合物/离子液体溶液的热力学仍然存在许多问题。在这项工作中，聚甲基丙烯酸正丁酯（PnBMA）在离子液体1-丁基-3-m乙基咪唑：双（三氟甲基磺酰基）亚胺（[BMIm][TFSI]）和1-乙基-3-甲基咪唑：TFSI （[EMIm][TFSI]）混合物中的低临界溶液温度（LCST）相行为通过透射率、光散射和小角中子散射测量来表征。通过改变离子液体的组成，可以很容易地调整几个相关的热力学参数。特别是，云点、旋量和θ温度都随着[BMIm]含量的增加而线性增加。用三种不同的方法确定了相互作用参数chi作为温度和浓度的函数，并比较了每种方法的结果。相互作用参数chi的熵和焓分量也随离子液体中[BMIm]含量的增加而线性变化，分别增加和减少。随着[BMIm]含量的增加，混合焓驱动力的增加压倒了混合熵惩罚的减少，导致溶解度的提高。从分子相互作用和定向溶剂化的角度讨论了这一结果。这项工作表征了一类非常有趣的聚合物溶液中一个代表性体系的溶液热力学，并提供了对其LCST相行为的分子机制的见解。
Ionic liquids feature a combination of properties that make them very interesting solvents for polymers, but many questions remain regarding the thermodynamics of polymer/ionic liquid solutions. In this work, the lower-critical-solution-temperature (LCST) phase behavior of poly(n-butyl methacrylate) (PnBMA) in mixtures of the ionic liquids 1-butyl-3-m ethylimidazolium:bis (trifluoromethylsulfonyl)imide ([BMIm][TFSI]) and 1-ethyl-3-methylimidazolium:TFSI ([EMIm][TFSI]) is characterized by transmittance, light scattering, and small-angle neutron scattering measurements. Several relevant thermodynamic parameters are easily tuned by varying the ionic liquid composition. In particular, the cloud point, spinodal, and Theta temperatures are all found to increase linearly with [BMIm] content. The interaction parameters, chi, are determined as a function of temperature and concentration using three different methods, and the results from each method are compared. The entropic and enthalpic components of the interaction parameter, chi, are also found to vary linearly with [BMIm] content in the ionic liquid, increasing and decreasing, respectively. The increase in the enthalpic driving force for mixing with increasing [BMIm] content dominates over the decrease in the entropic penalty for mixing, leading to improved solubility. This result is discussed in terms of molecular interactions and oriented solvation. This work characterizes the solution thermodynamics of one representative system in a very interesting class of polymer solutions, and provides insight into the molecular mechanisms underlying its LCST phase behavior.