Novel Polymer Microgel Dispersions with an Inverse Thermoreversible Gelation

本项目的目的是建立一个反向的热可逆凝胶化聚合物微凝胶的分散体。 它们在室温下是液体，但在高温下会变成固体。 其中心思想是设计和合成具有环境响应性的疏水键或氢键的聚合物微凝胶，其足以将微凝胶组装体保持在一起，但不会太强而导致絮凝。 与物理交联的凝胶如明胶相反，所提出的分散体的结构单元是胶体微凝胶。 随着温度的可调粒子间的潜力，这些微凝胶可以自组装成各种介观结构。 该项目包括五个目标。第一种是合成具有两个互穿聚合物网络（IPN）的微凝胶。 一个网络对温度变化做出响应，而另一个则没有。 这两个网络之间的平衡提供了合适的粒子间电位，导致逆热可逆凝胶化。二是设计和合成可生物降解的互穿网络微凝胶用于热凝胶分散体。 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（目标3）和具有氢键的两种不同微凝胶的混合物（目标4）。 最后一个目的是使用互穿网络微凝胶分散体作为一个模型系统，实验研究熔融动力学，堵塞相图，和粒子间的力量。 智力优点：这个项目是创新的，因为它的设计结合了联合收割机之间的平衡不同的聚合物，不同的结构和不同的粒子间的相互作用。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，它将导致一类新的聚合物微凝胶分散体与逆热可逆凝胶化。 与所有已知的分散体（包括硬球或原子系统）相比，具有单一聚合物浓度的新设计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提供一个模型系统来研究由于当前可用的胶体系统的限制而尚未完全探索的熔化和堵塞过程中的基本问题。该项目将通过合成可生物降解的微凝胶作为分散体中的构建块，为开发可注射药物递送液体开辟一条途径。 更广泛的影响：本研究中建立的基础科学不仅将对聚合物科学产生影响，还将对生物医学应用产生影响。 该计划将整合其本科教育的努力与两个现有的计划，促进研究经验：得克萨斯州数学与科学学院（TAMS）和罗纳德F。北德克萨斯大学麦克奈尔学士后成就计划。 从这个拟议的跨学科项目，研究生和本科生将获得宝贵的实验和分析技能，在生物聚合物和纳米结构材料的快速增长的领域。

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.