Lamellae Formation and Reorientation in Diblock Copolymers

本研究项目将使用分析和计算技术来研究两嵌段共聚物中片层相的形成、稳定性和粗化。尽管嵌段共聚物已经在工业上得到了广泛的应用，但依赖于高性能聚合物材料的新技术往往需要精确控制聚合物的微观结构及其自组装。通过高温各向同性相的温度淬火或溶剂浇注处理总是会导致形成由不同取向的片层的磁区或颗粒组成的多晶结构。本研究的重点是控制长程取向有序的机制，包括通过往复剪切改变片层相的取向，以及拓扑缺陷的运动及其对片层结构粗化的影响。在介观水平上进行了理论分析，以求在外加往复剪切作用下的非线性解，并阐明了其稳定性。明确考虑了微相之间的粘弹性对比度。此外，片层相的最长弛豫时间可能由拓扑缺陷的空间分布和运动决定。考虑了晶界、位错和位错的运动，以及它们对微观结构粗化时间和可能存在的渐近自相似的影响。本研究项目将使用解析和计算技术来研究两嵌段共聚物中片层相的形成、稳定性和粗化。尽管嵌段共聚物已经在工业上得到了广泛的应用，但依赖于高性能聚合物材料的新技术往往需要精确控制聚合物的微观结构及其自组装。高温各向同性相经温度淬火或溶剂浇注处理后，往往会形成由不同取向的片层的磁畴或颗粒组成的多晶结构。本研究的重点是控制长程取向有序性和拓扑缺陷运动的机制及其对片层结构粗化的影响。

0100903VinalsThis research project will use analytical and computational techniques to study the formation, stability and coarsening of lamellar phases in diblock copolymers. Although block copolymers are already widely used in industry, newer technologies that rely on high performance polymeric materials often require precise control of the polymer microstructure and its self-assembly. Processing by temperature quench or solvent casting from a high temperature isotropic phase always leads to the formation of a polycrystalline structure comprised of domains or grains of differently oriented lamellae. The focus of this research is on mechanisms controlling long-ranged orientational order, including the reorientation of lamellar phases by reciprocating shears, and the motion of topological defects and its effect on coarsening of the lamellar structure. A theoretical analysis is carried out at a mesoscopic level to find nonlinear solutions under imposed, reciprocating shears, as well as to elucidate their stability. Viscoelastic contrast between the microphases is explicitly taken into consideration. In addition, the longest relaxation times in the lamellar phase are likely to be determined by the spatial distribution and motion of topological defects. The motion of grain boundaries, disclinations (in two-dimensional samples), and dislocations is considered, as well as their effect on the coarsening times of the microstructure, and on the possible existence of asymptotic self-similarity.%%%This research project will use analytical and computational techniques to study the formation, stability and coarsening of lamellar phases in diblock copolymers. Although block copolymers are already widely used in industry, newer technologies that rely on high performance polymeric materials often require precise control of the polymer microstructure and its self-assembly. Processing by temperature quench or solvent casting from a high temperature isotropic phase always leads to the formation of a polycrystalline structure comprised of domains or grains of differently oriented lamellae.The focus of this research is on mechanisms controlling long-ranged orientational order and the motion of topological defects and its effect on coarsening of the lamellar structure.***