Structure, Energetics and Phase Behavior in Polyelectrolyte-Colloid Systems

聚电解质与小的相反电荷胶体之间的相互作用表现在一些重要的生物和技术现象上。为了使这些观测和当前的理论合理化，在定义明确的模型系统上进行实验是必不可少的。这样的实验将在聚电解质和三类定义明确的合成胶体颗粒-混合胶束、树枝状大分子和羧化Ficoll组分-以及蛋白质上进行。聚合物的相对分子质量、线电荷密度和链刚性会随着胶体尺寸和电荷的变化而发生系统的变化。广泛的技术，包括浊度和总强度、电泳光散射、QELS、光漂白后的荧光恢复、SANS、时间分辨荧光光谱和流变学，将被用来回答关于相互作用的能量、可溶性络合物的结构和相行为的问题。%除了解决基本问题和将理论与实验联系起来之外，这项工作将与(1)化学技术、(2)细胞生物学和(3)环境问题有关，如下所示。(1)聚电解质-胶体相互作用是水处理、造纸和预制陶瓷中稳定和絮凝的核心。(2)非特异性多离子-蛋白结合可能是控制蛋白多糖在细胞外基质中作用的重要现象。(3)聚电解质与吸附在沙/土上的胶束之间的络合物可能成为非挥发性污染物在水中迁移的障碍。参与这项工作的学生将接触到一种跨越理论和应用的高度多学科的方法。

The interactions between polyelectrolytes and small oppositely charged colloids are manifested in some important biological and technological phenomena. In order to rationalize these observations and current theory, experiments on well-defined model systems are essential. Such experiments will be carried out on polyelectrolytes in combination with three classes of well-defined synthetic colloid particles - mixed micelles, dendrimers, and carboxylated Ficoll fractions - and also with proteins. Polymer MW, linear charge density and chain stiffness will be varied systemically, along with colloid size and charge. A wide range of techniques, including turbidimetry and total intensity, electrophoretic light scattering, QELS, fluorescence recovery after photobleaching, SANS, time-resolved fluorescence spectroscopy and rheology will be used to answer questions about the energetics of interaction, the structure of soluble complexes, and phase behavior.%%%In addition to addressing fundamental questions and linking theory with experiment, the work will be of relevance to problems in (1) chemical technology, (2) cell biology, and (3) environmental issues, as follows. (1) Polyelectrolyte-colloid interactions are central to stabilization and flocculation in: water treatment, paper-making, and preceramics. (2) Non-specific polyion-protein association may be an important phenomenon controlling the role of proteoglycans in the extracellular matrix. (3) Complexes between polyelectolytes and micelles adsorbed on sand/soil may serve as barriers in the aquiferous migration of apolar pollutants. Students involved in this work will be exposed to a highly multidisciplinary approach that spans theory and applications.