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

从溶液中选择性地和可逆地去除大量溶质的能力仍然是环境修复、色谱法和药物递送等多种活动的目标。选择性需要精心设计的底物，用于固定具有特定功能和/或反应性的溶质。可逆性要求当系统受到外部刺激，如pH值、溶剂极性、温度或光的变化时，这些相同的底物释放结合的溶质。受控的可逆吸附允许基质再生和重复使用，这是可持续和环境友好的分离系统的基本特征。主客体化学和分子识别的进展解决了选择性问题，但很少有系统提供可逆行为，并且所有系统都限于特定的支持材料。即使当环境变化可以触发释放结合溶质，提出的机制描述基板溶质亲和力仍然是推测性的，在大多数情况下，功能化的基板具有有限的负载能力。能够从水溶液中选择性地和可逆地去除溶质具有巨大的实际后果。美国环境保护署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由化工厂排放的小型有机物，来自农业径流或与工业相关的活动（如运输和腐蚀）。已知这些有机污染物中的许多会损害肝脏、肾脏和/或中枢神经系统，并且一些构成潜在致癌物的风险。从受污染的场地清除这些溶质是昂贵的。在超级基金站点处操作泵和处理系统的年度成本可以超过每个站点每年1000万美元，并且在美国存在超过1000个超级基金站点。对水安全的类似关注导致欧盟对有机污染物的安全水平和点源排放实施严格限制。该项目的目的是设计新的分子基基质，能够特异性和可逆地去除水溶液中的溶质。将使用两种一般策略来官能化具有针对捕获和释放化学的特定溶质的涂层的宽范围的高表面积基底;树枝状聚合物和等离子体化学聚合物膜。这些表面将被设计为结合特定的溶质，然后在明确的触发后释放这些相同的溶质。线性和非线性光学方法将被用来确定吸附和解吸的目标，并推断吸附的机制的动力学。长远目标是开发实用、具成本效益的水处理吸附剂，使其可多次再生，大大减少现时不可逆吸附剂的制造及弃置对环境造成的影响。此项目是与美国蒙大拿州立大学的Robert步行者及玛丽.克洛宁格教授合作进行。

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.