Active Control of Sol-Gel-Sol Transitions of Aqueous Solutions of Doubly Responsive Hydrophilic Block Copolymers

双响应亲水嵌段共聚物水溶液溶胶-凝胶-溶胶转变的主动控制

• 批准号: 0906913
• 负责人: Bin Zhao
• 金额: $ 33万
• 依托单位: University of Tennessee Knoxville
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-06-01 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0906913&HistoricalAwards=false
• 关键词: Active; Control; Sol; Gel; Transitions

TECHNICAL SUMMARY:Owing to the intriguing transitions between free-flowing solutions and free-standing gels and the associated changes in structures and rheological properties, thermosensitive block copolymer micellar gels have received considerable attention and have found a wide range of applications. This project seeks to develop a strategy to actively control sol-gel/gel-sol transitions of aqueous solutions of doubly responsive hydrophilic block copolymers and to achieve multiple cycles of sol-gel-sol transitions under different environmental conditions. A series of hydrophilic block copolymers that can respond to two external stimuli will be synthesized by ?living?/controlled radical polymerization techniques including atom transfer radical polymerization and reversible addition fragmentation chain transfer polymerization. The functional monomers recently developed in the PI?s laboratory will be used to prepare these block copolymers along with monomers whose homopolymers have been reported to exhibit thermoresponsive properties in water. The hard gel boundary phase diagrams of aqueous solutions of these block copolymers under different environmental conditions will be mapped out by the tube inversion method and rheometry. The structures of micelles and micellar gels will be elucidated. The effects of various molecular parameters on the sol-gel-sol transitions will be investigated. A variety of characterization techniques will be employed in this research, including dynamic and static light scattering, rheometry, fluorescence spectroscopy, small angle X-ray and neutron scattering, differential scanning calorimetry, and transmission electron microscopy. The knowledge gained from this research will provide a general principle for design of multi-responsive aqueous micellar gels for technological applications. NON-TECHNICAL SUMMARY:The stimuli-responsive hydrophilic block copolymers developed from this research have potential applications in controlled encapsulation and triggered release of substances (e.g., drug molecules), tissue engineering, sensors, and many other emerging technologies. The knowledge gained from this work will enable rational design of multi-responsive aqueous gels for various applications. Moreover, this research project provides a strong setting for training of graduate and undergraduate students in the synthesis of well-defined block copolymers, characterization of molecular, micellar, and hierarchically self-assembled structures, and design of stimuli-responsive soft materials. The PI will continue his effort to develop a laboratory component for the introductory polymer chemistry course that he has been teaching. The PI is committed to help science teaching in K-12 education. He will work with local high school teachers and students in his laboratory through summer programs to develop new laboratory experiments for high school chemistry classes.

技术概述：由于自由流动溶液和独立凝胶之间的有趣转变以及相关的结构和流变性能的变化，热敏嵌段共聚物胶束凝胶受到了相当大的关注，并找到了广泛的应用。本项目旨在开发一种策略，主动控制双响应亲水性嵌段共聚物水溶液的溶胶-凝胶/凝胶-溶胶转变，并在不同环境条件下实现多循环的溶胶-凝胶-溶胶转变。通过对两种外界刺激反应的亲水性嵌段共聚物将被合成。可控自由基聚合技术包括原子转移自由基聚合和可逆加成破碎链转移聚合。最近在PI？S实验室将用于制备这些嵌段共聚物以及单体，其均聚物已被报道在水中表现出热响应特性。用管式反演法和流变法绘制了这些嵌段共聚物水溶液在不同环境条件下的硬凝胶边界相图。胶束和胶束凝胶的结构将被阐明。研究了不同分子参数对溶胶-凝胶-溶胶转变的影响。本研究将采用多种表征技术，包括动态和静态光散射、流变学、荧光光谱、小角度x射线和中子散射、差示扫描量热法和透射电子显微镜。从本研究中获得的知识将为设计用于技术应用的多反应水性胶束凝胶提供一般原则。非技术总结：本研究开发的刺激响应型亲水嵌段共聚物在物质（如药物分子）的受控封装和触发释放、组织工程、传感器和许多其他新兴技术方面具有潜在的应用前景。从这项工作中获得的知识将使各种应用的多反应水性凝胶的合理设计成为可能。此外，本研究项目为培养研究生和本科生在明确定义的嵌段共聚物的合成、分子、胶束和分层自组装结构的表征以及刺激响应软材料的设计方面提供了强有力的环境。PI将继续努力为他所教授的高分子化学入门课程开发一个实验室组件。PI致力于帮助K-12教育中的科学教学。他将通过暑期项目与当地高中教师和学生在他的实验室合作，为高中化学课开发新的实验室实验。