Theory of hierarchically structured soft matter

本研究计划的重点是开发新的概念、理论框架和方法，用于研究从大分子系统自组装的分层结构软物质。该研究将以嵌段共聚物为主要模型体系进行。嵌段共聚物是由两个或两个以上化学性质不同的子链或嵌段组成的大分子。不同块之间的斥力和链连通性之间的竞争驱动这些大分子形成具有不同大小和形状的纳米级结构域的有序结构或形态。例如，最近的实验和理论表明，嵌段共聚物可以自组装成极其复杂的球形填充相（所谓的Frank-Casper相），具有五种不同形状的结构域。嵌段共聚物形成具有不同物理性质域的有序纳米结构的能力为设计和控制具有理想形态的材料提供了强大的平台。这些层次化的纳米结构聚合物材料可以有许多有用的应用，包括用于光子晶体的周期性有序软材料，用于药物输送的纳米级囊泡，以及用于下一代光刻的亚纳米模式。这项研究计划的目标是发展基于分子的理论，以理解和预测分层结构软物质的出现、稳定性和物理性质。

This proposed research program focuses on the development of new concepts, theoretical frameworks, and methodologies for the study of hierarchically structured soft matter self-assembled from macromolecular systems. The study will be carried out using block copolymers as a primary model system. Block copolymers are macromolecules composed of two or more chemically distinct sub-chains or blocks. The competition between the repulsion between the different blocks and the chain connectivity drives these macromolecules to form ordered structures or morphologies with nanometer-sized domains of different sizes and shapes. For example, recent experiment and theory have demonstrated that block copolymers can self-assemble into an extremely complex spherical packing phase (the so-called Frank-Casper -phase) with five types of domains of different shapes. The ability of block copolymers to form well-ordered nanostructures with domains of very different physical properties provides a powerful platform to engineer and control materials with desirable morphologies. These hierarchically nanostructured polymeric materials could have many useful applications, including periodically ordered soft materials for photonic crystals, nanosized vesicles for drug delivery, and sub-nanometer patterns for next-generation lithography. The objective of this proposed research program is to develop molecule-based theories to understand and predict the emergence, stability, and physical properties of hierarchically structured soft matter. The formation of hierarchically structured polymeric materials involves a number of components with diverse physical attributes such as chain topology, molecular size, rigidity, and chirality. Furthermore, the interactions between these monomers could be more complicated than the usual non-specific van der Waals interactions. Examples of these complicated interactions are hydrogen bonding and electrostatic interactions. To study systems with these diverse properties, I will develop theoretical frameworks for polymeric systems composed of complex architectures and rigid and/or chiral components. Specifically, my proposed research program includes three inter-related topics: (1) The structure and phase transition of multiblock copolymers, focusing on the emergence, mechanism of formation, and properties of hierarchically structured polymeric materials; (2) The phase behavior of polymeric systems containing semiflexible, chiral and associative components, focusing on the effects of molecular size, shape, rigidity and association on the self-assembled phases; (3) The structure and morphology of amphiphilic block copolymer solutions, focusing on the formation and property of nanosized aggregates including bilayer membranes.