Deuteration Effects on Micellization, Crystallization and Melting of Styrene-block-Butadiene Copolymers in Dilute Near-Critical Solutions

NSF/CTS/Radosz CTS-0625338项目摘要/摘要氢气对苯乙烯-嵌段-丁二烯共聚物在稀近临界溶液中胶束化、结晶和熔融的影响怀俄明大学这个为期一年的纳米相关项目的目标是探索氢化苯乙烯-丁二烯嵌段共聚物在稀近临界溶液中的相行为，其中溶剂是在其临界温度以下或以上使用的压缩流体。在这种近临界溶液中，块状聚合物的胶束有序-无序(ODT)转变不仅可以通过升高温度引起临界胶束温度，还可以通过增加压力引起临界胶束压力。所有这些在近临界稀溶液中的压力诱导转变，包括胶束化、结晶、熔化和液-液转变(浊点)，都是快速、可重复性的，并且易于准确检测，这通常与在浓缩溶液、熔体和混合物中加热和冷却引起的缓慢转变形成对比。这是因为聚合物溶液在近临界溶剂中具有低粘度和高扩散速率。因此，这种解决方案提供了一种可靠而有效的方法来表征用于中子散射研究的氚聚合物样品的胶束化和结晶情况，在这种情况下，需要氢化来增强对比度。这项工作的实验方面是表征两对其他相同的氢化和非氢化样品的浊点分离、结晶、熔融和胶束化，例如具有可变的1，2/1，4加入量和可变结晶性的聚苯乙烯-b-聚丁二烯(PS-b-PBD)(仅通过富含1，4的样品的完全或部分加氢获得)。超临界丙烷和丙烯中的这些相变和胶束转变将通过怀俄明大学软材料实验室的高压动态光散射来确定。共聚物样品将在橡树岭国家实验室的纳米材料科学中心通过活性阴离子聚合合成。这项提议的工作的智力价值在于独特的实验结果，这些结果将有助于理解由氚引起的胶束化、结晶和熔化的差异。这个项目将教育学生描述导致纳米结构材料的自组装分子的特征。这些学生不仅将接触到PI实验室的实验表征方法，还将接触到橡树岭国家实验室的合成和中子散射设施。此外，用于表征块状聚合物胶束溶液的高压动态光散射方法将被纳入研究生和本科生的热力学和聚合物科学课程。该项目还将间接促进基于胶束的纳米颗粒回收技术，如冷冻干燥回收，例如，通过提供基本知识，如何从近临界溶剂中回收干燥胶束，而不必冻结与制造药物和基因传递纳米颗粒相关的溶剂。

NSF/CTS/Radosz CTS-0625338Project Abstract /SummaryDeuteration Effects on Micellization, Crystallization and Melting of Styrene-block-Butadiene Copolymers in Dilute Near-Critical SolutionsUniversity of WyomingThe goal of this one-year nano-related project is to explore the phase behavior of deuterated styrene-block-diene copolymers in dilute near-critical solutions, where the solvent is a compressed fluid used either below or above its critical temperature. The micellar order-disorder (ODT) transitions of blocky polymers in such near-critical solutions can be induced not only by increasing temperature, which leads to critical micelle temperature, but also by increasing pressure, which leads to critical micelle pressure. All such pressure-induced transitions in dilute near-critical solutions, including micellization, crystallization, melting, and fluid-liquid transitions (cloud points), are fast, reproducible, and easy to detect accurately, often in contrast to the sluggish transitions induced by heating and cooling in concentrated solutions, melts and blends. This is because polymer solutions in near-critical solvents have low viscosity and high diffusion rates. Therefore, such solutions offer a robust and efficient approach to characterizingmicellization and crystallization of deuterated polymer samples used for neutron scattering studies, where deuteration is needed to enhance the contrast. The experimental aspect of this work is to characterize cloud-point separation, crystallization, melting, and micellization of deuterated and non-deuterated pairs of otherwise identical styreneblock- diene samples, such as polystyrene-b-polybutadiene (PS-b-PBD), with variable 1,2/1,4 addition and variable crystallizability (obtained by complete or partial hydrogenation of the 1,4-rich samples only). These phase and micellar transitions in supercritical propane and propylene will be determined from high-pressure dynamic light scattering in the Soft Materials Laboratory at the University of Wyoming. The copolymer samples will be synthesized via living anionic polymerization in the Center for Nanophase Materials Sciences at Oak Ridge National Laboratory. The intellectual merit of the proposed work lies in unique experimental results that will help understand differences in micellization, crystallization, and melting caused by deuteration.Broader Impact. This project will educate students in characterizing self assembling molecules that lead to nanostructured materials. These students will not only be exposed to the experimental characterization methods in the PI's lab, but also to the synthesis and neutron scattering facilities at the Oak Ridge National Laboratory. Furthermore, the high-pressure dynamic light scattering method of characterizing micellar solutions of blocky polymers will be incorporated in the graduate and undergraduate thermodynamics and polymer science classes. This project will alsoindirectly contribute to the micelle-based nanoparticle recovery technology, such as freeze-dry recovery, for example, by providing basic understanding how to recover dry micelles from near-critical solvents without having to freeze the solvent, which is relevant to manufacturing drug and gene delivery nanoparticles.