Generating Nonnative Structures in Binary Ionic Liquid Mixtures for Tunable Phase Equilibria Properties

离子液体是完全由离子组成的物质，并且可以通过结合广泛的阳离子和阴离子而被设计为作为液体存在。由于其基本上不挥发的性质和独特的物理化学性质，它们已成为潜在的环境友好化学品。通过明智地选择离子上的阳离子、阴离子或官能团，可以赋予离子液体所需的物理、化学和生物性质，使其成为真正的设计溶剂。尽管这种组合方法可以潜在地用于产生多达一百万种离子液体，但离子液体领域中的持续挑战是许多离子液体显示出不利的传输性质，限制了它们在工业过程中的使用。此外，具有在工业应用（例如气体分离）感兴趣的范围内的传输性质的离子液体通常含有氟化离子，由于毒性和差的生物降解性，提高了它们的生产成本和环境问题。 具有不同组成的离子液体的二元混合物可以潜在地提供分子相互作用的精确微调以产生所需的性质。根据一种估计，存在十亿种二元离子液体组合;因此，非常期望先验地预测二元离子液体混合物的性质。然而，目前，缺乏基本知识的设计规则，可以适用于得出这样的结论。建议的研究是面向填补这一关键的知识gap.The建议是由以下假设指导的，即非理想的二元离子液体混合物中的非本地分子相互作用发生时，两种离子液体的氢键能力相差很大的组合;非理想的行为反映在非线性依赖的气体的溶解度的二元混合物的组成。该假设的有效性将被测试（i）确定在何种程度上建立新的相互作用的二元混合物组成的离子液体在其氢键能力的差异很大，和（ii）评估这种相互作用的效果上的二元离子液体混合物与气体，如二氧化碳和甲烷的相平衡特性。将进行分子动力学模拟，以阐明分子水平的相互作用存在于由两种离子液体组成的混合物中，而自由能计算和蒙特卡罗方法将用于计算这些混合物中的物质的相平衡。拟议的研究和教育的整合旨在创造一个智力刺激的环境，培养研究生和本科生了解分子现象在设计有效的化学系统中的作用。拟议的外联计划针对的是来自不同背景的学生和STEM领域代表性不足的人群。

Ionic liquids are substances that are composed entirely of ions and can be designed to exist as liquids by combining a wide range of cations and anions. They have emerged as potentially environmentally benign chemicals due to their essentially nonvolatile nature and unique physicochemical properties. By judiciously selecting the cation, anion or functional groups on the ions, desired physical, chemical and biological properties can be imparted to ionic liquids making them truly designer solvents. Although such a combinatorial approach can potentially be exploited to generate as many as one million ionic liquids, a continuing challenge in the field of ionic liquids is that many ionic liquids display unfavorable transport properties limiting their use in industrial processes. Further, ionic liquids with transport properties in the range of interest for industrial applications, such as gas separations, usually contain fluorinated ions raising their production cost and environmental concern due to toxicity and poor biodegradability. Binary mixtures of ionic liquids with different compositions can potentially provide precise fine-tuning of the molecular interactions to generate desired properties. According to one estimate, there are one billion binary ionic liquid combinations; thus, it is highly desirable to predict a priori the properties of binary ionic liquid mixtures. However, at present, there is a lack of fundamental knowledge regarding the design rules that can be applied to arrive at such a conclusion. The proposed research is geared toward fulfilling this critical knowledge gap.The proposal is guided by the hypothesis that nonideality in the binary ionic liquid mixtures in terms of non-native molecular interactions occurs when two ionic liquids differing widely in their hydrogen bonding ability are combined; the nonideal behavior is reflected in the nonlinear dependence of solubility of gases on the composition of the binary mixture. The validity of the hypothesis will be tested by (i) determining the extent to which novel interactions are established for binary mixtures composed of ionic liquids differing widely in their hydrogen bonding ability and (ii) evaluating the effect of such interactions on the phase equilibria properties of binary ionic liquids mixtures with gases, such as carbon dioxide and methane. Molecular dynamics simulations will be carried out to elucidate molecular level interactions present in the mixtures composed of two ionic liquids while free-energy calculations and Monte Carlo methods will be employed for calculation of phase equilibria of substances in these mixtures. The proposed integration of research and education aims at creating an intellectually stimulating environment for training graduate and undergraduate students on understanding the role of molecular phenomena in designing efficient chemical systems. The proposed outreach plan is targeting students from diverse backgrounds and underrepresented populations in STEM fields.