Control of Photopolymerization Kinetics and Thermodynamics in Self-assembled Surfactant Systems to Direct Polymer Nanostructure

职务名称：自组装表面活性剂体系中光聚合动力学和热力学的控制以指导聚合物纳米结构Allan Guymon机构：最近的研究表明，纳米技术，或在非常小的尺寸尺度上控制材料结构的能力，可以提供传统材料无法获得的独特和有用的特性。 在纳米尺度上控制类似于塑料和隐形眼镜的材料中的有机聚合物结构在改善性能方面显示出巨大的前景。最近在使用表面活性剂或肥皂在聚合物网络中开发纳米级结构方面取得了进展，涉及自组装，这是特别感兴趣的。 这些表面活性剂（皂）分子在水的存在下形成溶致液晶（LLC），其组织成有序的纳米尺度特征，其可用于引导或模板化聚合物结构。由LLC相模板化的聚合物组成的材料在其对温度的响应方面显示出巨大的潜力。 它们可以用作再生生物组织的膜和支架。 在聚合过程中控制结构仍然是困难的，结构通常与原始模板有很大不同，因此不太有用。 对于该项目，PI将使用具有优化稳定性的系统中的聚合速度来指导LLC模板内的聚合物结构演变。总体目标是在聚合之前和聚合期间控制光聚合动力学和热力学，以及表面活性剂/单体化学，以理解和指导使用LLC介质形成的聚合物的结构演变。PI将调节表面活性剂和单体的化学结构和反应性，以增强LLC自组装的热力学稳定性，从而改善生长的聚合物网络和模板之间的相互作用。这些系统将使用计算方法建模，以评估模板混合物的热力学稳定性。据信，自由基光聚合的使用将在成功完成这项工作中发挥关键作用。 光聚合提供了在宽范围的温度下以几分之一秒的时间进行聚合的能力，从而允许动力学捕获否则在化学上不利的聚合物纳米结构。 研究了由传统的链状和硫醇烯分步生长光聚合机理形成的聚合物纳米结构。 聚合动力学与聚合物结构演化之间的联系是项目成功的关键。 聚合速率、转化率和相分离将使用光差示扫描量热法并通过红外和拉曼光谱实验进行真实的实时监测。热力学和动力学将相关的纳米结构之前，期间和聚合后，使用许多表征技术（小角X射线散射，电子显微镜，固态和溶液NMR）。PI认为，这项研究将概述指导和控制最终聚合物纳米结构所需的动力学和热力学因素。该项目将提供一种相对简单的方法来可控地生产纳米结构的有机聚合物材料。具有可控纳米尺度几何形状的聚合物将表现出独特的传输特性和尺寸选择性，这对于诸如水净化、刺激响应、组织支架和水凝胶等应用的进展至关重要。这项研究的一个主要主题是学生教育。 将强调本科生和研究生研究人员在发现学习环境中的广泛参与。 少数民族的本科生和研究生研究人员将被招募作为NSF REU计划的一部分，在纳米科学和纳米技术。此外，聚合物，纳米技术和化学工程的重要性将被带到高中学生作为两个模块的一部分，每年在当地和农村高中化学课。

Title: Control of Photopolymerization Kinetics and Thermodynamics in Self-assembled Surfactant Systems to Direct Polymer NanostructureProposal #1438486PI: C. Allan GuymonInstitution: University of IowaRecent research has shown that nanotechnology, or the ability to control material structures at very small size scales, can provide unique and useful properties not accessible in traditional materials. Controlling organic polymer structure in materials similar to plastics and contact lenses at the nanometer scale has shown great promise in improving performance. There have been recent advances in developing nanoscale structure in polymer networks using surfactant, or soap, have involved self-assemblies, which are of particular interest. These surfactant (soap) molecules form lyotropic liquid crystals (LLC) in the presence of water that organize into ordered nanometer scale features which can be used to direct, or template, polymer structures. Materials made up of polymers templated by LLC phases have shown great potential in their response to temperature. They can be used as membranes and scaffolds to regenerate biological tissue. Controlling the structure during the polymerization is still difficult with structures typically being much different than the original template, and thus less useful. For this project the PI will use the speed of polymerization in systems with optimized stability to direct polymer structure evolution within LLC templates. The overall goal is to control photopolymerization kinetics and thermodynamics before and during polymerization, and surfactant/monomer chemistry to understand and direct the structural evolution of polymers formed using LLC media. The PI will modulate surfactant and monomer chemical structure and reactivity to reinforce thermodynamic stability of the LLC-self-assembly to improve interactions between the growing polymer network and the template. These systems will be modeled using computational methods to evaluate the thermodynamic stability of the templating mixtures. It is believed that the use of radical photopolymerization will play a pivotal role in successful completion of this work. Photopolymerization provides the ability to polymerize in fractions of a second at a wide range of temperatures, thereby allowing kinetic trapping of otherwise thermodynamically unfavorable polymer nanostructures. Polymer nanostructures formed from both traditional chain and thiol-ene step growth photopolymerization mechanisms will be investigated. Critical for project success is the connection between the polymerization kinetics and polymer structure evolution. Polymerization rate, conversion, and phase separation will be monitored in real time using photo-differential scanning calorimetry and through infra-red and Raman spectroscopy experiments. Thermodynamics and kinetics will be correlated to nanostructure before, during, and after polymerization using numerous characterization techniques (small angle X-ray scattering, electron microscopy, solid state and solution NMR). The PI believes that this research will outline the kinetic and thermodynamic factors necessary to direct and control the ultimate polymer nanostructure.This project will provide a relatively simple approach to controllably produce nanostructured organic polymeric materials. Polymers with controlled nano-scale geometries will exhibit unique transport properties and size selectivity, which are critical for advances in applications such as water purification, stimuli response, tissue scaffolds, and hydrogels. A prevailing theme for this research will be student education. Extensive involvement of undergraduate and graduate researchers in a discovery learning environment will be emphasized. Minority undergraduate and graduate researchers will be recruited as part of the NSF REU Program in Nanoscience and Nanotechnology. Additionally, the importance of polymers, nanotechnology, and chemical engineering will be brought to high school students as part of two modules presented yearly to chemistry classes at both local and rural high schools.