Theory, simulations and applications for nanostructured polymeric materials

这项研究计划的重点是涉及两类结构聚合物的技术重要问题，特别是嵌段共聚物和聚合物刷。普通聚合物是通过将相同的单体单元连接在一起形成长链分子而合成的，而嵌段共聚物是由不同的单体组成的部分（或块）组成的。化学上不同的块分离的自然趋势导致这些分子自组装成具有纳米级结构域的各种复杂结构（或形态）。将具有不同特性的聚合物组合成有序的纳米结构的能力为控制材料特性提供了一种强有力的方法。作为可持续聚合物中心（CSP）的一部分，我们将利用这种控制来改善可再生植物基聚合物材料的性能，希望它们能与传统的石油基材料竞争，甚至超越它们。此外，嵌段共聚物的自组装成纳米级结构在纳米技术中有许多有用的应用。例如，我们感兴趣的是开发用于药物输送的纳米尺寸囊泡，在纳米尺度上对表面进行图案设计的有效方法，以及智能环境响应纳米结构。聚合物刷代表了另一类结构聚合物，在纳米技术中有许多复杂的应用。它们是通过末端将聚合物以足够高的密度附着在表面上而形成的，这种密度使得聚合物从表面伸展出去。我们将研究由外部电场控制的带电聚电解质电刷，用于纳米级致动器和通过薄膜的纳米级孔门控等应用。

This research proposal focuses on technologically important problems involving two classes of structured polymers, specifically block copolymers and polymeric brushes. While ordinary polymers are synthesized by joining together identical monomer units to form long-chain molecules, block copolymers consist of sections (or blocks) made from different monomers. The natural tendency for chemically distinct blocks to separate causes these molecules to self-assemble into various and often elaborate structures (or morphologies) with nanometer-sized domains. The ability to combine polymers with different characteristics into well-ordered nanostructures provides a powerful way of controlling material properties. As part of the Center for Sustainable Polymers (CSP), we will use this control to improve the properties of renewable plant-based polymeric materials in hopes they will compete or even outperform conventional petroleum-based materials. Furthermore, the self-assembly of block copolymers into nano-sized structures leads to many useful applications in nanotechnology. For instance, we are interested in the development of nano-sized vesicles for drug delivery, efficient methods for patterning surfaces on the nanoscale, and smart environmentally-responsive nanostructures. Polymeric brushes represent another class of structured polymers with many sophisticated applications in nanotechnology. They are formed by attaching polymers to a surface by their ends at a sufficiently high density that the crowding causes the polymers to stretch away from the surface. We will study charged polyelectrolyte brushes controlled by an external electric field for applications such as nano-sized actuators and gating nano-sized pores through thin membranes.   To study these systems, my group will continue our development of self-consistent field theory (SCFT), for which I am regarded as one of the world's leading experts. SCFT permits exact mean-field calculations for structured polymers using coarse-grained microscopic models. It is a tremendous improvement over previous approaches and has been rewarded by a series of remarkable successes. The theory has been able to model very subtle effects, predict behaviour later to be confirmed by experiment, correct major experimental errors, and play a vital role in experimental studies. Because of its microscopic nature, SCFT is highly predictive and allows access to many quantities that experiments cannot measure. As a result, SCFT routinely provides simple intuitive explanations for its predictions. Despite its amazing track record with ordered structures, SCFT becomes inaccurate for fluctuating disordered morphologies. However, techniques for incorporating these fluctuations into SCFT are now emerging with the advent of field theoretic simulations (FTS), and we will continue our work on a promising Monte Carlo variant (MC-FTS).