Catch and Release Chemistry: Reversible Adsorption on Dendrimer and Polymer Functionalized Surfaces

选择性和可逆地从溶液中去除大量溶质的能力仍然是环境修复、层析和药物输送等各种活动的目标。选择性需要精心设计的底物来固定具有特定功能和/或反应活性的溶质。可逆性要求当体系受到外部刺激时，这些相同的底物释放结合的溶质，如pH、溶剂极性、温度或光线的变化。可控的可逆吸附允许基质再生和重复使用，这是可持续和对环境友好的分离系统的基本特征。主客体化学和分子识别方面的进展解决了选择性问题，但很少有系统提供可逆行为，而且都局限于特定的载体材料。即使环境变化可以触发结合溶质的释放，所提出的描述底物-溶质亲和力的机制仍然是推测的，并且在大多数情况下，功能化的底物具有有限的负载能力。能够选择性和可逆地去除水溶液中的溶质具有巨大的实际意义。美国环保局承认并设定了饮用水(包括瓶装水)中90多种污染物的浓度上限。这些污染物中有一半以上是化工厂排放的小有机物种，来自农业径流，或来自与工业相关的活动(如运输和腐蚀)。众所周知，这些有机污染物中的许多都会损害肝脏、肾脏和/或中枢神经系统，有些还具有潜在致癌物的风险。将这些溶质从受污染的地点移走是昂贵的。超级基金每个站点每年运行泵和治疗系统的成本可能超过1000万美元，全美有1000多个超级基金站点。对水安全的类似担忧导致欧盟对有机污染物的安全水平和点源排放施加了严格的限制。该项目的目的是设计新的基于分子的底物，能够特定和可逆地去除水溶液中的溶质。将使用两种一般策略来使大范围的高表面积基材功能化，所述涂层针对用于捕捉和释放化学的特定溶质；树枝状大分子和等离子机械聚合物薄膜。这些表面将被设计成结合特定的溶质，然后在明确定义的触发之后释放这些相同的溶质。将使用线性和非线性光学方法来确定目标的吸附和解吸的动力学，并推断吸附的机理。该项目的长期目标是开发实用、经济高效的水处理吸附剂，可多次再生，极大地减少制造和处置现有不可逆吸附剂对环境的影响。该项目与美国蒙大拿州立大学的Robert Walker教授和Mary Cloninger教授合作。

The ability to selectively and reversibly remove large quantities of solutes from solution remains the goal of activities as diverse as environmental remediation, chromatography, and drug delivery. Selectivity requires carefully designed substrates for immobilizing solutes with specific functionality and/or reactivity. Reversibility requires that these same substrates release the bound solutes when the system is subjected to external stimuli such as changes in pH, solvent polarity, temperature, or light. Controlled, reversible adsorption allows substrates to be regenerated and reused, an essential feature of sustainable and environmentally benign separation systems. Advances in host-guest chemistry and molecular recognition address the selectivity issue, but few systems provide for reversible behavior and all are limited to specific support materials. Even when environmental changes can trigger the release of bound solutes, proposed mechanisms describing substrate-solute affinity remain speculative, and in most cases, the functionalized substrates have limited loading capacities. Being able to selectively and reversibly remove solutes from aqueous solution has enormous practical consequences. The United States Environmental Protection Agency recognizes and sets upper concentration limits for more than 90 contaminants in drinking water (including bottled water). More than half of these contaminants are small organic species that are discharged by chemical factories, result from agricultural runoff, or arise from industry-related activities (such as transportation and corrosion). Many of these organic contaminants are known to damage the liver, kidneys and/or central nervous system, and some pose risks as potential carcinogens. Removing these solutes from contaminated sites is expensive. The annual cost of operating pump and treat systems at Superfund sites can exceed $10 million per year per site, and more than 1000 Superfund sites exist across the United States. Similar concerns about water safety have led the European Union to impose strict limits on safe levels and discharges from point sources of organic contaminants.The aim of this project is to design new molecularly-based substrates capable of specific and reversible removal of solutes from aqueous solutions. Two general strategies will be used to functionalize a wide range of high surface area substrates with coatings that target specific solutes for catch and release chemistry ; dendrimers and plasmachemical polymer films. These surfaces will be designed to bind specific solutes and then to release these same solutes following a well-defined trigger. Linear and nonlinear optical methods will be used to determine the kinetics of adsorption and desorption of the targets and to infer the mechanisms of adsorption. The long term objective is to develop practical, cost-effective adsorbents for water treatment that can be regenerated many times, greatly reducing the enviromental impact arising from the manufacture and disposal of current irreversible absorbents.This project is in collaboration with Prof. Robert Walker and Prof. Mary Cloninger of Montana State University, USA.