Department of Chemistry, Department of Applied Physics and Materials Science, and ¡MIRA! the Center for Materials Interfaces in Research and Applications, Northern Arizona University, Flagstaff, Arizona, USA.
Department of Chemistry, The College of New Jersey, Ewing, New Jersey, USA.
Phys Chem Chem Phys. 2022 Jun 8;24(22):13720-13729. doi: 10.1039/d2cp01530g.
The deep eutectic solvent choline and geranate (CAGE) has shown promise in many therapeutic applications. CAGE facilitates drug delivery through unique modes of action making it an exciting therapeutic option. We examine the behavior of aqueous CAGE solutions at a liquid-vapor interface. We find that the liquid-vapor interface induces large oscillations in the density, which corresponds to spontaneous segregation into regions enriched with geranate and geranic acid and other regions enriched with water and choline. These heterogeneities are observed to extend nanometers into the liquid. Additionally, we find that the geranate and geranic acid orient so that their polar carboxyl or carboxylate groups are on average pointed toward the layer containing water and choline. Finally, we report surface tension and thermal expansion coefficients for various concentrations of aqueous CAGE. We find a non-monotonic trend in the surface tension with concentration. The structural and thermodynamic properties we report provide a new perspective on CAGE behavior, which helps deduce the action of CAGE in more sophisticated systems and inspire other studies and applications of CAGE and related materials.
深共晶溶剂胆碱和葵酸酯（CAGE）在许多治疗应用中显示出了前景。CAGE 通过独特的作用方式促进药物传递，使其成为一种令人兴奋的治疗选择。我们研究了液态 CAGE 溶液在气液界面处的行为。我们发现，气液界面会引起密度的大幅振荡，这对应于自发分离成富含葵酸酯和葵酸的区域和富含水和胆碱的其他区域。这些非均相性观察到延伸到液体中数纳米。此外，我们发现葵酸酯和葵酸定向，使得它们的极性羧基或羧酸盐基团平均指向含有水和胆碱的层。最后，我们报告了各种浓度的水溶液 CAGE 的表面张力和热膨胀系数。我们发现表面张力与浓度之间存在非单调趋势。我们报告的结构和热力学性质为 CAGE 的行为提供了新的视角，有助于推断 CAGE 在更复杂系统中的作用，并激发对 CAGE 和相关材料的其他研究和应用。
