Structure and Dynamics of Soft Condensed Matter

液晶、凝胶和脂质膜都是软凝聚态物质的例子，这些材料的特点是分子间相互作用弱、机械柔软且对热波动敏感。其中许多材料是二维、准二维或分形的；由较小成分（例如颗粒、聚合物或脂质分子）自组装而成；并表现出丰富的行为，包括相变、图案形成和非线性材料特性。它们也具有很大的实际意义——隐形眼镜是由聚合物凝胶制成的，而液晶构成了许多显示屏的基础——而且它们可以用作更复杂的生物系统的模型。该领域有潜力产生有趣的物理和新颖的应用。 我们的重点是几个系统中微观结构和宏观材料特性之间的关系。在这个提案中，我们计划在三个领域开展工作。我们将研究由疏水性和导电嵌段组成的共聚物形成的聚合物薄膜的微观结构；这些研究的目标是从根本上了解离子聚合物的微观结构和电导率之间的关系，从而对这些材料进行明智的设计，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。 我们还开始研究由给电子聚合物和分子受体的混合物形成的聚合物薄膜中的纳米结构，以应用于有机光伏器件。同样，我们的目标是了解纳米结构是如何确定的，以便为更好的材料设计提供信息。第三个研究领域探索屈服应力流体、仅在施加临界应力时才流动或屈服的材料的微观结构和流变学之间的关系；日常的例子包括泥浆、剃须泡沫和蛋黄酱。我们研究这些材料散射的光，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。这些研究的目标是揭示屈服应力行为的普遍方面，从而促进微观理论的发展。

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.