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

摘要/总结氘化对苯乙烯-丁二烯嵌段共聚物在稀近临界溶液中的胶束化、结晶和熔融的影响怀奥明大学这个为期一年的纳米相关项目的目标是探索氘化苯乙烯-丁二烯嵌段共聚物在稀近临界溶液中的相行为，其中溶剂是低于或高于临界温度的压缩流体。在这种近临界溶液中，块状聚合物的胶束有序-无序（ODT）转变不仅可以通过增加温度（达到临界胶束温度）来诱导，也可以通过增加压力（达到临界胶束压力）来诱导。在稀释的近临界溶液中，所有这些由压力引起的转变，包括胶束化、结晶化、熔化和流-液转变（云点），都是快速的、可重复的，并且易于准确检测，这与在浓溶液、熔体和混合物中加热和冷却引起的缓慢转变形成鲜明对比。这是因为聚合物溶液在接近临界的溶剂中具有低粘度和高扩散速率。因此，这种溶液提供了一种强大而有效的方法来表征用于中子散射研究的氘化聚合物样品的胶束化和结晶，在中子散射研究中需要氘化来增强对比度。这项工作的实验方面是表征云点分离、结晶、熔化和胶束化的氘化和非氘化对的苯乙烯嵌段二烯样品，如聚苯乙烯-b-聚丁二烯（PS-b-PBD），具有可变的1,2/1,4加成和可变的结晶性（仅通过富1,4样品的完全或部分氢化获得）。超临界丙烷和丙烯中的这些相和胶束转变将在怀俄明大学软材料实验室的高压动态光散射中确定。共聚物样品将在橡树岭国家实验室的纳米相材料科学中心通过活阴离子聚合合成。所提出的工作的智力价值在于独特的实验结果，这将有助于理解由氘化引起的胶束，结晶和熔化的差异。更广泛的影响。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。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备。此外，高压动态光散射表征块状聚合物胶束溶液的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，例如冻干回收，通过提供基本的了解如何从接近临界的溶剂中回收干燥胶束，而无需冷冻溶剂，这与制造药物和基因传递纳米颗粒有关。

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.