Department of Biotechnology, Indian Institute of Technology Madras, Chennai 600036, India.
J Am Chem Soc. 2010 Sep 8;132(35):12511-6. doi: 10.1021/ja1055005.
Molecular aggregation is a complex phenomenon that is difficult to study in detail experimentally. Here, we elucidate the formation of ionic liquid-in-carbon dioxide (IL-in-CO(2)) microemulsions via a computer simulation technique that demonstrates the entire process of self-aggregation at the atomic level. Our study reveals direct evidence of the existence of stable IL droplets within a continuous CO(2) phase through amphiphilic surfactants. The microstructure of the nanodroplets matches very well with the small-angle neutron scattering data. A detailed investigation of the structural and energetic properties explains why guanidium acetate-based IL-in-CO(2) microemulsions showed a greater stability than imidazolium hexafluorophosphate-based microemulsions in recent spectroscopic experiments. In contrast to the existing hypothesis in literature, the study reveals that the stability of the microemulsions mainly pertains to the IL anion-headgroup interactions, while the cations play a secondary role. The detailed atomic level understanding provides a deeper insight that could help in designing new surfactants for improved IL uptake in CO(2).
分子聚集是一种复杂的现象，很难在实验中详细研究。在这里，我们通过计算机模拟技术阐明了离子液体-二氧化碳（IL-in-CO(2)）微乳液的形成，该技术展示了在原子水平上的整个自聚集过程。我们的研究通过两亲性表面活性剂直接证明了在连续 CO(2)相中存在稳定的 IL 液滴。纳米液滴的微观结构与小角中子散射数据非常吻合。对结构和能量特性的详细研究解释了为什么基于胍基乙酸盐的 IL-in-CO(2)微乳液在最近的光谱实验中比基于六氟磷酸盐的 imidazolium 微乳液具有更高的稳定性。与文献中现有的假设相反，该研究表明微乳液的稳定性主要取决于 IL 阴离子头基相互作用，而阳离子则起次要作用。详细的原子水平理解提供了更深入的见解，有助于设计新的表面活性剂以提高 CO(2)中的 IL 吸收。
