Molecular Design of Novel Polymer Materials Based onBottlebrush Macromolecules

聚合技术的重大进展使得能够合成具有精确控制的分子尺寸和明确形状的超支化结构。高度支化大分子最独特的例子之一是由许多密集接枝到线性链（主链）的聚合物侧链组成的分子瓶刷。密集接枝分支之间的强烈空间排斥会影响刚度并确保单个瓶刷的高度延伸构象，并减少浓溶液和熔体中分子之间的重叠。这些显着的特征为制造基于洗瓶刷的材料提供了机会，其物理特性不同于由线性聚合物组成的传统材料。该项目的目标是开发洗瓶刷聚合物的分析和数值模型，为设计新型超软和​​超韧材料提供指导。通过分子的解缠结可以大大增强聚合物的柔软度。在熔体中，瓶刷结构促进解缠结，从而产生不寻常的流变特性，即平台模量比线性链熔体中通常观察到的低 2-3 个数量级。我们建议研究交联洗瓶刷的结构与所得弹性体的柔软度之间的关系。已经证明，可以通过合成具有不同刚度的网络来改善聚合物凝胶的性能。洗瓶刷的硬度可以通过改变其厚度来控制。我们建议研究由不同刚度的交联瓶刷组成的互穿网络的特性。我们的方法是综合研究，使用分子动力学和蒙特卡罗模拟技术以及缩放和平均场概念来发展对瓶刷熔体和网络的理论理解。

Significant progress in polymerization techniques allows synthesis of hyperbranched architectures with precisely controlled molecular dimensions and well-defined shapes. One of the most distinctive examples of highly-branched macromolecules are molecular bottlebrushes composed of many polymer sidechains densely grafted to a linear chain (backbone). Strong steric repulsion between densely grafted branches affects stiffness and ensures highly extended conformations of individual bottlebrushes and reduces overlap between molecules in concentrated solutions and melts. These remarkable features provide access to fabrication of bottlebrush based materials with physical properties that are distinct from conventional materials composed of linear polymers. The goal of this project is to develop analytical and numerical models of bottlebrush polymers that will provide guidelines for designing novel super-soft and super-tough materials. Softness of polymers can be greatly enhanced by disentanglement of molecules. In melts, bottlebrush architecture promotes disentanglement resulting in unusual rheological properties, i.e. plateau modulus is 2-3 orders of magnitude lower than typically observed in linear chain melts. We propose to study the relationship between architecture of cross-linked bottlebrushes and softness of the resulting elastomer. It has been demonstrated that properties of polymer gels can be improved by synthesizing networks with different stiffness. Stiffness of bottlebrushes can be controlled by varying their thickness. We propose to study properties of interpenetrating networks composed of cross-linked bottlebrushes with different stiffness. Our approach is a combined study using molecular dynamics and Monte-Carlo simulation techniques as well as scaling and mean-field concepts to develop a theoretical understanding of bottlebrush melts and networks.