Equilibrium Dynamics of Dense Colloids and Polymers: X-ray Photon Correlation Spectroscopy Studies

这是一个实验凝聚态物理项目，将研究胶体，聚合物和相关流体的动力学特性，通常被称为软mattes。虽然软物质的静态结构已经得到了广泛的研究，但在最相关的长度尺度（10-100 nm）上的动态特性却很难研究。该项目将对软材料的集体动力学产生新的见解，特别强调集中和纠缠系统。为了获得所需的散射波矢量，将采用新兴的x射线光子相关光谱技术（XPCS）。流体动力相互作用和纠缠在各向同性胶棒悬浮液动力学中的作用也将被研究。在胶体/聚合物混合物中，胶态液体-胶态气体临界点附近的动态临界行为是另一个感兴趣的话题。了解这种动态普遍性类预测的发散粘度如何影响与颗粒间分离相当的长度尺度上的动力学，将提高我们对蛋白质结晶的理解。将研究纠缠聚合物体系的动力学，并与相关理论进行比较。重要的是，这些研究将为聚合物动力学的再现模型提供定量测试，这些模型是以前无法进入的长时间、短距离和柔性聚合物的体系。在这个项目下训练的学生将为充分利用这个国家在同步辐射研究方面的主要投资做出贡献。此外，在该计划下，x射线光子相关光谱的进一步发展将有助于新一代更强大的x射线源的科学案例。复杂流体，如流体中固体颗粒的细小分散体（胶体分散体）、长链聚合物的混合物以及油、水和肥皂的混合物，是一类重要的材料，通常被称为“软物质”。虽然这类软材料的静态结构已经得到了广泛的研究，但复杂流体的分子运动研究要困难得多。在这个项目中，一种新的基于同步加速器的x射线散射方法- x射线光子相关光谱-将用于检查小距离上的非常缓慢的运动，并且应该对胶体和聚合物系统内的热运动产生新的见解。将得到的结果与现有的理论进行比较，将对这些理论进行关键的检验。所获得的见解可能对提高对诸如蛋白质结晶或聚合物流体流动等多种现象的理解和控制具有实际意义。在这个项目下训练进行尖端x射线散射研究的学生将为利用国家在同步辐射研究方面的主要投资贡献所需的人才库。毕业生将为开展学术、工业或政府研究做好充分准备。在该计划下，x射线光子相关光谱学的进一步发展将有助于新一代更强大的x射线源的科学研究。

This is an experimental condensed matter physics project that will investigate the dynamical properties of colloids, polymers and related fluids, commonly termed soft mattes. While the static structure of soft matter has been extensively examined, the dynamical properties on the most relevant length scales (10-100 nm) have been much more difficult to study. This project will yield new insight into the collective dynamics of soft materials, with particular emphasis on concentrated and entangled systems. To achieve the scattering wave vectors required, the emerging technique of x-ray photon correlation spectroscopy (XPCS) will be employed. The role of hydrodynamic interactions and entanglements in the dynamics of isotropic suspensions of colloidal rods will also be studied. Dynam-ical critical behavior near the colloidal liquid-colloidal gas critical point in colloid/polymer mixtures is another topic of interest. Understanding how a divergent viscosity, predicted for this dynamic universality class, affects the dynamics on length scales comparable to the inter-particle separation will improve our understanding of protein crystallization. The dynamics of entangled polymer systems will be investigated and compared to relevant theories. Importantly, these investigations will provide quantitative tests of the reptation model of polymer dynamics in the previously-inaccessible regime of long times, short distances, and flexible poly-mers. Students trained under this project will contribute to the pool of talent needed to fully utilize this nation's major investment in synchrotron-radiation-based research. In addition, the further development of x-ray photon correlation spectroscopy under this program will contribute to the scientific case for a new generation of even-more-powerful x-ray sources.%%%Complex fluids, such as fine dispersions of solid particles within a fluid (colloidal dispersions), blends of long-chain polymers, and mixtures of oil, water and soap are an important class of materials, commonly termed "soft matter". While the static structure of such soft materials has been studied extensively, the molecular motions of complex fluids have been much more difficult to study. In this project, a novel synchrotron-based x-ray scatter-ing method - x-ray photon correlation spectroscopy - will be used to examine very slow motions on small distances, and should yield new insight into the thermal movements within colloidal and polymeric systems. Comparisons between the results obtained and available theories will provide a critical test of the theories. The insights gained may be practically important for improved understanding and control of such diverse phenomena as protein crystallization or the flow of polymeric fluids. Students trained to carry out cutting-edge x-ray scattering research under this program will contribute to the pool of talent needed to make use of this nation's major investment in synchrotron-radiation-based research. The graduates will be well-prepared to carry out academic, industrial, or governmental research. The further development of x-ray photon correlation spectroscopy under this program will contribute to the scientific case for a new generation of even-more-powerful x-ray sources.