Kinetics of Polymer Interfacial Reactions

聚合物界面反应动力学

• 批准号: 1206191
• 负责人: Jeffrey Koberstein
• 金额: $ 40.5万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-01 至 2015-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1206191&HistoricalAwards=false
• 关键词: Kinetics; Polymer; Interfacial; Reactions

TECHNICAL SUMMARY: The overall goal of the proposed research is to develop a fundamental understanding of the factors that influence interfacial reactions of long chain polymer molecules. The grafting of polymers to a surface is an important aspect in a myriad of applications ranging from biosensors, wherein bio macromolecules such as DNA are tethered to substrates to prepare microarrays, to steric stabilization, wherein a synthetic polymer is tethered to a surface to form a brush that prevents particle agglomeration. An intimate knowledge of these interfacial grafting reactions is essential to optimize these applications. Toward this end, model interfacial "click" reactions between a substrate modified with an azide function monolayer and a polymer terminated with an alkyne group are studied by infrared spectroscopy using a multiple internal reflection technique that samples the absorbance of the azide absorbance band which disappears upon reaction. Azides and alkynes react to form triazole groups in a process referred to as "click" chemistry due to its high yield and high chemoselectivity. The kinetics of solution reactions at interfaces are mediated by the effects of crowding as already grafted molecules inhibit additional polymer molecules from approaching and reacting to the surface. Factors that influence surface crowding are therefore under investigation including the nature of the solvent, the polymer molecular weight, the density of surface functional groups, the surface tension and the nature of polymer surface interactions. Interfacial reactions between the functional polymers and azide-functional nanoparticles are also monitored by transmission infrared spectroscopy in order to assess the effects of surface curvature. Interfacial melt reactions are investigated in a parallel program of research to be executed by undergraduates. The data collected are used to validate theoretical treatments of polymer interfacial reactions. NON-TECHNICAL SUMMARY:Long chain polymer molecules are often attached by their ends to a surface to meet the needs of many high-tech industrial applications. Microarray sensors, for example, used to detect biological warfare agents or to map genomes, are prepared by attaching natural biological polymers such as DNA, carbohydrates and proteins to the surface or a silicon wafer or microchip. Polymer brushes, synthetic polymers attached by their ends to solid substrates, are used in a myriad of applications including the stabilization of colloidal particles, imparting biological stealth to drug delivery vehicles and providing protein resistance in microfluidic devices to name but a few. The common feature in all of these applications is the need to covalently bond a polymer chain by its end to a substrate of interest at controlled surface density. The focus of this research proposal is to gain a fundamental understanding of such polymer reactions at surfaces and the factors that affect them. The rates of reactions of two complementary reactive functional groups are well understood for reactions in solution, however, the rates of reactions at surfaces, are not fully understood because they are influenced by a number of physical and thermodynamic parameters that are associated with the presence of a surface. The rates of polymer surface reactions are studied by an infrared spectroscopy technique that can quantitatively and directly measure the reaction rates of the surface bound reactive chemical group without disturbing the progress of the reaction. Parameters under investigation include the nature of the solvent if present, the size of the polymer molecule, the properties of the underlying surface, and the surface density of functional groups. The knowledge generated by this research will help in the design of industrial products ranging from biological sensors that can rapidly identify disease to devices that can resist biological fouling. The fundamental principles identified by the research are incorporated into several courses taught by the PI including the physical chemistry of macromolecules and polymer surface phenomenon. A diverse group of undergraduate and PhD students working on the research project receive training in materials and surface science, exposure to how intellectual property is protected, and learn how to communicate research results to the public, skills that are important in any field they decide to pursue after graduation.

技术摘要：本研究的总体目标是对影响长链聚合物分子界面反应的因素有一个基本的了解。将聚合物接枝到表面是众多应用中的一个重要方面，从生物传感器（其中生物大分子如DNA被束缚在基底上以制备微阵列）到空间稳定（其中合成聚合物束缚在表面上以形成防止颗粒团聚的刷子）。深入了解这些界面接枝反应对于优化这些应用至关重要。为此，通过红外光谱研究了用叠氮化物功能单层改性的基材和以炔基封端的聚合物之间的模型界面“点击”反应，使用多重内反射技术对反应时消失的叠氮化物吸光带的吸光度进行采样。叠氮化物和炔烃在称为“点击”化学的过程中反应形成三唑基团，因为其高产率和高化学选择性。界面处溶液反应的动力学是由拥挤效应介导的，因为已接枝的分子会抑制其他聚合物分子接近表面并与其发生反应。因此，正在研究影响表面拥挤的因素，包括溶剂的性质、聚合物分子量、表面官能团的密度、表面张力和聚合物表面相互作用的性质。还通过透射红外光谱监测功能聚合物和叠氮化物功能纳米粒子之间的界面反应，以评估表面曲率的影响。界面熔融反应是在由本科生执行的并行研究计划中进行研究的。收集的数据用于验证聚合物界面反应的理论处理。非技术摘要：长链聚合物分子通常通过其末端附着在表面上，以满足许多高科技工业应用的需求。例如，用于检测生物战剂或绘制基因组图谱的微阵列传感器是通过将天然生物聚合物（例如DNA、碳水化合物和蛋白质）附着到表面或硅晶片或微芯片上来制备的。聚合物刷是末端附着在固体基质上的合成聚合物，具有多种应用，包括稳定胶体颗粒、赋予药物输送载体生物隐形性以及在微流体装置中提供蛋白质耐受性等。所有这些应用的共同特征是需要将聚合物链的末端以受控的表面密度共价键合到感兴趣的基材上。该研究计划的重点是对表面的此类聚合物反应以及影响它们的因素有一个基本的了解。对于溶液中的反应，两个互补反应性官能团的反应速率已被充分理解，然而，表面反应速率尚未完全理解，因为它们受到与表面存在相关的许多物理和热力学参数的影响。通过红外光谱技术研究聚合物表面反应速率，该技术可以定量、直接测量表面结合的反应性化学基团的反应速率，而不干扰反应进程。正在研究的参数包括溶剂的性质（如果存在）、聚合物分子的大小、底层表面的性质以及官能团的表面密度。这项研究产生的知识将有助于工业产品的设计，从可以快速识别疾病的生物传感器到可以抵抗生物污垢的设备。研究确定的基本原理被纳入 PI 教授的几门课程中，包括大分子的物理化学和聚合物表面现象。从事该研究项目的不同群体的本科生和博士生接受了材料和表面科学方面的培训，了解知识产权的保护方式，并学习如何向公众传达研究成果，这些技能对于他们毕业后决定从事的任何领域都很重要。