Novel Polymer Microgel Dispersions with an Inverse Thermoreversible Gelation

这个项目的目标是创建具有逆热可逆凝胶化的聚合物微凝胶分散体。它们在室温下是液体，但在升高的温度下变成固体。核心思想是设计和合成具有环境反应性疏水键或氢键的聚合物微凝胶，这些聚合物微凝胶足以将微凝胶聚集在一起，但不会太强而导致絮凝。与物理交联凝胶（如明胶）相反，提出的分散体的构建块是胶体微凝胶。这些微凝胶具有温度可调的粒子间电位，可以自组装成各种介观结构。这个提议的项目包括五个目标。首先是合成具有两个互穿聚合物网络的微凝胶。一个网络对温度变化有反应，另一个则没有。这两种网络之间的平衡提供了一个合适的粒子间势，从而导致逆热可逆凝胶化。二是设计和合成用于热胶化分散体的可生物降解IPN微凝胶。热胶凝微凝胶分散体的概念将扩展到包括具有核-壳结构的微凝胶（目的3）和具有氢键的两种不同微凝胶的混合物（目的4）。最后，以IPN微凝胶分散体为模型体系，对熔融动力学、干扰相图和粒子间力进行了实验研究。智力优势：这个提议的项目是创新的，因为它的设计结合了不同聚合物，不同结构和不同粒子间相互作用之间的平衡。聚合物微凝胶的合成将与紫外可见光谱、静态和动态光散射以及流变学方法的准确表征相关。如果成功，它将导致一种具有逆热可逆凝胶化的新型聚合物微凝胶分散体。与所有已知的分散体（包括硬球体或原子系统）相比，新设计的具有单一聚合物浓度的微凝胶分散体可以通过升高温度从液体变为凝胶，或者通过降低温度变为晶体或玻璃。这种微凝胶分散体可以为研究熔融和干扰过程中的基本问题提供一个模型系统，这些问题由于目前可用的胶体系统的限制而没有得到充分的探讨。拟议的项目将通过合成可生物降解的微凝胶作为分散体的构建块，为开发可注射药物输送液体开辟一条道路。更广泛的影响：在这项研究中建立的基础科学将不仅对聚合物科学产生影响，而且对生物医学应用产生影响。该项目将把本科教育工作与两个现有的促进研究经验的项目结合起来：德克萨斯州数学与科学学院（TAMS）和北德克萨斯大学的罗纳德·f·麦克奈尔后学士学位成就项目。从这个跨学科的项目中，研究生和本科生将在快速发展的生物聚合物和纳米结构材料领域获得宝贵的实验和分析技能。

The objective of this proposed project is to create dispersions of polymer microgels with an inverse thermo-reversible gelation. They will be liquids at room temperature but become solids at an elevated temperature. The central idea is to design and synthesize polymer microgels with environmentally responsive hydrophobic or hydrogen bonding that are sufficient to hold the microgel assembly together but not too strong to cause flocculation. In contrast to physically crosslinked gels such as gelatin, the building blocks of proposed dispersions are colloidal microgels. With a temperature tunable interparticle potential, these microgels can self-assemble into various mesoscopic structures. This proposed project consists of five aims. The first is to synthesize microgels with two interpenetrating polymer networks (IPN). One network is responsive to a temperature change and the other is not. The balance between these two networks provides a suitable interparticle potential, resulting in an inverse thermoreversible gelation. The second is to design and synthesize biodegradable IPN microgels for the use in thermally gelling dispersions. The concept of thermally gelling microgel dispersions will be extended to include microgels with core-shell structures (Aim 3) and to a mixture of two different microgels with hydrogen bonding (Aim 4). The last aim is to use the IPN microgel dispersion as a model system to experimentally study dynamics of melting, the jamming phase diagram, and the interparticle forces. Intellectual merit: This proposed project is innovative because its designs combine the balances between different polymers, different structures and different inter-particle interactions. The polymer microgel synthesis will be correlated with accurate characterizations by UV-visible spectroscopy, static and dynamic light scattering and rhelogical methods. If successful, it will lead to a new class of polymer microgel dispersions with an inverse thermoreversible gelation. In contrast to all known dispersions including hard spheres or atomic systems, the newly designed microgel dispersion with a single polymer concentration can change from a liquid to a gel by increasing temperature, or to a crystal or to a glass by decreasing temperature. This microgel dispersion can provide a model system to study the fundamental problems in melting and jamming processes that have not been fully explored due to limitations of current available colloidal systems. The proposed project will open an avenue to the development of injectable drug delivery liquids by synthesizing biodegradable microgels as building blocks in the dispersions. Broader impacts: The basic sciences established in this research will have impacts not only in polymer sciences but also in biomedical applications. This program will integrate its undergraduate educational efforts with two existing programs that promote research experiences: the Texas Academy of Mathematics and Science (TAMS) and the Ronald F. McNair Post-baccalaureate Achievement Program at University of North Texas. From this proposed inter-disciplinary project, both graduate and undergradaue students will gain valuable experimental and analytical skills in the rapidly growing fields of biopolymers and nanostructured materials.