International Collaboration in Chemistry: A Comprehensive Computational/Experimental Analysis of the Hofmeister Effect

该国际化学合作奖在法国由法国国家研究机构（ANR）和美国国家科学基金会共同资助，通过化学部的大分子，超分子和纳米化学计划，支持罗格斯大学新玩法分校的Laurence Romsted，大卫凯斯和罗纳德绍尔博士与尾田玲子博士之间的国际合作，Michel Laguerre（均来自法国欧洲化学与生物研究所）和Dario Bassani（来自法国CNRS分子科学研究所）。该项目的基本目标是表征离子对主要双子两亲物水溶液性质的特定影响。该团队将系统地改变两亲物的结构，并使用各种各样的抗衡离子来确定控制聚集体结构的力的平衡从分子水平到本体溶液性质的变化。将合成具有癸基和十二烷基尾的阳离子双子两亲物，其具有完全和部分甲基化的头基和各种抗衡离子，例如，Hofmeister系列的典型无机抗衡离子，以及有机抗衡离子，例如各种链长的烷基羧酸盐和烷基磷酸盐。通过使用物理、化学和模拟方法的组合，研究人员将确定物理性质之间的相关性（例如，临界胶束浓度、电离度、以及反离子和水的聚集数和界面浓度），如通过化学捕集和通过使用组合的分子动力学/密度泛函理论方法的模拟所确定的。模拟还将提供有关聚集体中尾部、头群、反离子和水的整体组织的新信息。对单链类似物的平行研究将突出双子表面活性剂亚甲基桥的重要性。由于化学捕获和分子动力学模拟对聚集体结构没有任何假设，因此发现两亲物结构、缔合物类型和聚集体物理性质之间的相关性将加深目前的理解，并为控制缔合胶体聚集行为的微妙力平衡提供新的见解。胶体和表面化学中尚未解决的挑战是对离子特异性对胶体和生物界面性质的影响的连贯解释，1888年，Hofmeister首次证明了盐对蛋白质溶解度的特殊影响。从那时起，许多经验观察到的订单已被公布，包括离子特定的影响各种水溶液性质的自组装离子缔合胶体，如胶束，微乳液和囊泡。这个合作项目提供了一个系统的方法来了解控制两亲聚合物结构的分子间力的相互作用。结果应该通过帮助选择用于特定应用的两亲物（目前是试错程序）而具有现实影响，并且应该增强软材料的实用性，例如，通过改变它们的结构来改变它们的结构。该项目新颖的多学科方法得益于两个国家的六名合作者的互补专业知识：Oda博士和Bassani博士将获得聚集体的精确物理性质测量值; Romsted博士将使用其小组的化学捕集方法确定界面水和反离子浓度; Laguerre博士、Case博士和Sauers博士的模拟应该为双子胶束界面处的头基、抗衡离子和水之间的特定相互作用提供新的见解。这项研究合作还将为本科生、研究生和博士后研究员提供高级培训。他们将沉浸在一个基本的和智力上具有挑战性的项目中，该项目包括各种实验方法与美国和法国实验室模拟相结合的经验，以及在聚集体和分子水平上表征两亲溶液的讨论。

This International Collaboration in Chemistry award, co-funded in France by the Agence Nationale de la Recherche (ANR) and in the United States by the National Science Foundation, through the Macromolecular, Supramolecular, and Nanochemistry Program of the Chemistry Division, supports an international collaboration between Drs. Laurence Romsted, David Case, and Ronald Sauers, all from Rutgers University, New Brunswick, and Drs. Reiko Oda, Michel Laguerre (both from the Institut Europeen de Chimie et de Biologie, France), and Dario Bassani (from the Institut des Science Molecularier CNRS, France). The fundamental goal of the project is the characterization of ion-specific effects on the properties of aqueous solutions of primarily gemini amphiphiles. The team will systematically vary amphiphile structure and use a wide variety of counterions to identify the shifts in the balance of forces controlling aggregate structure from the molecular level to bulk solution properties. Cationic gemini amphiphiles with decyl and dodecyl tails will be synthesized, with fully and partially methylated headgroups and a variety of counterions, e.g., the typical inorganic counterions of the Hofmeister series, but also organic counterions, such as alkylcarboxylates and alkylphosphates of various chain lengths. By using a combination of physical, chemical, and simulation methods, the researchers will determine correlations between physical properties (e.g., critical micelle concentration, ionization degree, and aggregation number and interfacial concentrations of the counterions and water), as determined by chemical trapping and by simulation using a combined molecular dynamics/density functional theory approach. The simulations will also provide new information on the overall organization of the tails, headgroups, counterions, and water within the aggregate. Parallel studies on single chain analogs will highlight the importance of the methylene bridge of the gemini surfactants. Because chemical trapping and molecular dynamic simulations make no assumptions about aggregate structure, correlations discovered between amphiphile structure, counterion type and aggregate physical properties will deepen current understanding and provide new insight into the delicate balance of forces that controls aggregation behavior of association colloids.One of the oldest, unresolved challenges in colloid and surface chemistry is a coherent explanation for ion-specific effects on the properties of colloids and biointerfaces, first demonstrated in 1888 by Hofmeister as a specific salt effect on the solubility of a protein. Since then, many empirically observed orders have been published including ion-specific effects on a variety of aqueous solution properties of self-assembling ionic association colloids such as micelles, microemulsions and vesicles. This collaborative project offers a systematic approach toward understanding the interplay of intermolecular forces controlling amphiphile aggregate structures. Results should have real-life impact by aiding in selection of amphiphiles for particular applications (currently a trial-and-error procedure) and should enhance the utility of soft materials, e.g., by tuning their structures simply by changing the counterion. This project's novel multidisciplinary approach benefits from the complementary expertise of six collaborators in two countries: Drs. Oda and Bassani will obtain precise physical property measurements on the aggregation; Dr. Romsted will use his group's chemical trapping method to determine interfacial water and counterion concentrations; simulations by Drs. Laguerre, Case, and Sauers should provide new insight into specific interactions between headgroups, counterions, and water at gemini micelle interfaces. This research collaboration will also provide advanced training for undergraduate and graduate students and postdoctoral fellows. They will be immersed in a fundamental and intellectually challenging project that includes experience with a variety of experimental approaches combined with simulations in laboratories in the US and France, and in discussions on characterizing amphiphile solutions at the aggregate and molecular levels.