Doubly Thermosensitive Block and Star Copolymers from Living Radical Polymerizations: Synthesis, Phase Transitions, and Applications

技术概要：本项目旨在开发定义明确的热敏嵌段和星星共聚物，其在水中表现出双重热诱导相变，以实现对分子量和分子结构对相行为的影响的基本理解，并阐明温度诱导自组装在水中的结构。具体而言，各种线性和星星嵌段共聚物的分子量控制，窄的分子量分布，和明确的结构将通过活性自由基聚合技术合成。最近在PI实验室开发的功能单体将被用来构建这些共聚物沿着与单体，其相应的均聚物已被报道表现出热敏特性。这些聚合物在水中的相变将通过比浊法，变温1H NMR光谱，荧光光谱，动态和静态光散射，差示扫描量热法和流变学测量进行研究。分子量和分子结构是否以及如何影响嵌段共聚物的响应性能将得到系统的研究。这些共聚物在水中自组装形成的纳米结构将通过透射电子显微镜来阐明。本研究所获得的知识将为设计具有多重转变的温敏性水溶性聚合物提供指导。双温敏共聚物在催化和物质触发释放方面的应用也将受到关注。随着纳米技术和生物技术的快速发展，人们迫切需要能够对外部刺激做出反应的智能材料。本研究所得到的双温敏性水溶性高分子材料在药物传递、化学传感器、催化、生物纳米技术等方面具有潜在的应用前景。此外，该研究项目为培养学生在高分子合成，表征，设计和制造刺激响应材料方面提供了一个很好的环境。各级学生将被纳入PI的研究和教育活动。PI还将与当地高中教师合作，通过在他的实验室暑期课程，为高中化学课开发动手实验。

TECHNICAL SUMMARY:This project seeks to develop well-defined thermosensitive block and star copolymers that exhibit double thermo-induced phase transitions in water, to achieve fundamental understanding of the effects of molecular weight and molecular structure on the phase behavior, and to elucidate the structures of temperature-induced self-assemblies in water. Specifically, a variety of linear and star block copolymers with controlled molecular weights, narrow molecular weight distributions, and well-defined architectures will be synthesized by living radical polymerization techniques. The functional monomers recently developed in the PIs laboratory will be used to construct these copolymers along with monomers whose corresponding homopolymers have been reported to exhibit thermoresponsive properties. The phase transitions of these polymers in water will be investigated by turbidimetry, variable temperature 1H NMR spectroscopy, fluorescence spectroscopy, dynamic and static light scattering, differential scanning calorimetry, and rheology measurement. Whether and how the molecular weight and molecular structure affect the responsive properties of block copolymers will be systematically studied. The nanostructures formed from self-assembly of these copolymers in water will be elucidated by transmission electron microscopy. The knowledge gained from this research will provide a guideline for designing thermosensitive water-soluble polymers with multiple transitions. The applications of doubly thermosensitive copolymers in catalysis and triggered release of substances will be pursued. NON-TECHNICAL SUMMARY:With the rapid advance of nanotechnology and biotechnology, intelligent materials that can respond to external stimuli are much needed. The double-thermosensitive water-soluble polymers from this research have potential for practical applications in drug delivery, chemical sensors, catalysis, and bio-nanotechnology. Moreover, this research project provides an excellent setting for training of students in polymer synthesis, characterization, design and fabrication of stimuli-responsive materials. Students at all levels will be integrated into the PIs research and education activities. The PI will also work with local high school teachers through summer programs in his laboratory to develop hands-on experiments for high school chemistry classes.