Structure and Dynamics of Soft Condensed Matter

液晶、凝胶和脂质膜都是软凝聚物质的例子，这些材料的特征在于弱的分子间相互作用、机械柔软性和对热波动的敏感性。这些材料中的许多是二维的、准二维的或分形的;通过较小组分（例如颗粒、聚合物或脂质分子）的自组装形成;并且表现出丰富的行为范围，包括相变、图案形成和非线性材料性质。它们也有很大的实际意义--隐形眼镜是由聚合物凝胶制成的，液晶是许多显示屏的基础--它们可以用作更复杂的生物系统的模型。这个领域有可能产生有趣的物理和新颖的应用。 我们的重点是在几个系统的微观结构和宏观材料性能之间的关系。在这项建议中，我们计划在三个方面开展工作。我们将研究由疏水性和导电性嵌段组成的共聚物形成的聚合物膜的微观结构;这些研究的目标是实现对离子聚合物中微观结构和导电性之间关系的基本理解，从而使这些材料的知情设计，这对于它们在聚合物电解质膜燃料电池中的应用至关重要。 我们还开始研究由供电子聚合物和分子受体的共混物形成的聚合物膜中的纳米结构，以应用于有机光伏器件。同样，我们的目标是了解如何确定纳米结构，以告知更好的材料的设计。第三个研究领域探索屈服应力流体的微观结构和流变学之间的关系，这些材料只有在施加临界应力时才会流动或屈服;日常的例子包括泥浆，剃须泡沫和蛋黄酱。我们研究这些材料的散射光，以研究小长度尺度下的扩散和弹性，并表征材料的微观结构。这些研究的目的是揭示屈服应力行为的普遍性，从而发展微观理论。

Liquid crystals, gels and lipid membranes are all examples of soft condensed matter, materials that are characterized by weak intermolecular interactions, mechanical softness, and a susceptibility to thermal fluctuations. Many of these materials are either two-dimensional, quasi-two dimensional, or fractal; are formed by self-assembly of smaller components such as particles, polymers or lipid molecules; and exhibit a rich range of behaviour including phase transitions, pattern formation, and non-linear material properties. They are also of great practical interest - contact lenses are made of polymeric gels, and liquid crystals form the basis for many display screens - and they can be used as models of more complicated biological systems. This field has the potential to produce both interesting physics and novel applications. Our focus is on the relationship between microscopic structure and macroscopic material properties in several systems. In this proposal, we plan to work in three areas. We will study the microstructure of polymer films formed from copolymers consisting of hydrophobic and conducting blocks; the goal of these studies is to achieve fundamental understanding of the relationship between microstructure and conductivity in ionic polymers, leading to informed design of these materials, which is critical for their application in polymer electrolyte membrane fuel cells. We are also starting studies of nanostructure in polymer films formed from blends of electron-donating polymers and molecular acceptors for application to organic photovoltaic devices. Again, the goal is to understand how the nanostructure is determined to inform design of better materials. A third research area explores the relationship between microstructure and rheology in yield-stress fluids, materials that flow or yield only when a critical stress is applied; everyday examples include mud, shaving foam and mayonnaise. We study the light scattered by these materials to study diffusion and elasticity at small length scales and to characterize the microstructure of the material. The goal of these studies is to uncover universal aspects of yield stress behaviour, leading to the development of microscopic theories.