Design of Molecular Gels with Exceptional Structural, Dynamic and Mechanical Properties

在这项由化学系高分子、超分子和纳米化学项目资助的项目中，乔治城大学的理查德·G·韦斯教授正在开发具有特殊性质的分子凝胶剂(小分子聚集成三维网络，可以固定大量液体)，例如能够可逆地转化为自由流动的液体。这项研究的一个主要目标是发展结构简单的分子凝胶剂的形状和功能与其凝胶性质之间的基本关系。要做到这一点，需要解决两个基本的科学问题：“什么是有效的分子凝胶剂？”以及“如何设计凝胶剂结构，以提供具有相当独特的结构和机械性能的材料？”这项研究的结果有望提供对基础科学和应用科学都很重要的信息，并填补目前分子结构和自组装之间的巨大理解差距，这些差距导致除了凝胶外，还有一系列自组织材料。其中几种凝胶可能在艺术品保护、石油回收和食品化学等应用中有用。另一个非常重要的影响是对年轻科学家的培训，包括那些在代表性不足的群体和来自发展中国家的科学家。所有级别的学生--博士后到高中--都有机会通过出席会议并在会议上展示他们的研究成果，以及通过与世界各地其他合作实验室的学生直接互动来融入科学界。所选的凝胶剂可以从商业上获得(例如，乙二胺四乙酸、乙亚胺表面活性剂和聚乙烯亚胺)或天然存在的(例如，鞘氨醇、葡萄糖胺和12-羟基硬脂酸)分子。或者，凝胶剂很容易从相关分子中合成。使用Hansen或分析液体性质的其他参数集预先选择作为凝胶剂最合适补充的溶剂。这些凝胶旨在提供“特殊”性能，例如在破坏性剪切后具有可变恢复率的高度触变性、由热和光化学引起的凝胶纤维内分子堆积变化引发的凝胶到凝胶的转变、以及通过添加或移除中性三原子气体(如二氧化碳)而引发的等温溶胶-凝胶转变。几种光谱、热力学和动力学技术可用于表征本研究的结构/官能化关系。

In this project funded by the Macromolecular, Supramolecular and Nanochemistry program of the Chemistry Division, Professor Richard G. Weiss of Georgetown University is developing 'molecular gelators' (small molecules that aggregate into 3-dimensional networks which immobilize large amounts of a liquid) with special properties, such as the ability to transform reversibly into free-flowing liquids. A primary objective of this research is to develop fundamental relationships between the shapes and functionalities of structurally simple molecular gelators and the properties of their gels. To do so, two fundamental scientific questions are being addressed: "What constitutes an efficient molecular gelator?" and "How can the gelator structures be designed to provide materials with rather unique structural and mechanical properties?" The results from this research are expected to contribute information that is important to both basic and applied science and to fill current large gaps of understanding between molecular structure and self-assembly that lead to a wide range of self-organized materials in addition to gels. Several of the gels may be useful in applications that include art conservation, oil recovery, and food chemistry. Another very important impact is the training of young scientists, including thosein under-represented groups and from developing countries. Students at all levels--postdoctoral to high school- are given opportunities to become integrated within the scientific community by attending and presenting their research results at conferences and by interacting directly with students in other collaborating labs throughout the world.The gelators selected are commercially available (e.g., ethylenediaminetetraacetic acid, Ethomeen surfactants, and polyethylenimines) or naturally occurring (e.g., sphingosine, glucamine, and 12-hydroxystearic acid) molecules. Alternatively, the gelators are easily synthesized from related molecules. Solvents that are most appropriate complements to the gelators are pre-selected using Hansen or other parameter sets that dissect liquid properties. The gels are designed to provide 'exceptional' properties, such as high degrees of thixotropy with variable recovery rates after destructive shear, gel-to-gel transitions initiated by thermally and photochemically induced changes of the molecular packing within gel fibers, and isothermal sol-gel transitions induced by adding or removing a neutral triatomic gas (such as CO2). Several spectroscopic, thermodynamic and kinetic techniques are available for characterizing the structural/functionality relationships for this study.