Grains and Defects in Block Copolymers

9901951 BalsaraAn实验研究，旨在获得一个基本的了解的因素，控制颗粒和缺陷结构的嵌段共聚物，提出。嵌段共聚物属于表现出从无序相到具有液晶对称性的有序纳米结构的破胶相变的一般类别的材料。典型的例子包括层状结构和排列在六边形晶格上的圆柱体。然而，在这些材料中的相干秩序被限制在有限的区域或晶粒，伴随着缺陷。该建议解决了三个问题：晶粒的成核，缺陷动力学，和宏观变形的晶粒的微观响应。我们将使用的主要工具，以获得晶粒结构是去偏振光散射。在我们的实验室中建立了光学性质和嵌段共聚物颗粒结构（尺寸、形状和颗粒间相关性）之间的关系。光学实验将增加电子显微镜，中子散射和流变学。初步研究所需的样品已经通过高真空阴离子聚合法合成;必要时将合成更多的样品。获得该资助的学生将在聚合物合成、光谱和色谱法表征聚合物、光散射、X射线和中子以及凝聚态物理等领域接受教育。这种跨学科培训在政府和工业研究实验室中变得越来越重要。

9901951BalsaraAn experimental study, aimed at obtaining a fundamental understanding of the factors that control grain and defect structure in block copolymers, is proposed. Block copolymers belong to a general class of materials that exhibit a symmetry-breaking phase transition from a disordered phase to ordered nanostructures with liquid crystalline symmetry. Typical examples include lamellae, and cylinders arranged on a hexagonal lattice. However, coherent order in these materials is restricted to finite regions or grains, with concomitant defects. This proposal addresses three issues: nucleation of grains, defect dynamics, and the microscopic response of grains to macroscopic deformation. The primary tool that we will use to obtain the grain structure is depolarized light scattering. The relationship between optical properties and block copolymer grain structure (size, shape, and inter-grain correlations) was established in our laboratory. The optical experiments will be augmented by electron microscopy, neutron scattering, and rheology. Samples required for the initial studies have already been synthesized by high vacuum anionic polymerization; additional samples will be synthesized as necessary.The students who will be supported by this grant will be educated in the areas of polymer synthesis, polymer characterization by spectroscopy and chromatography, scattering of light, X-rays, and neutrons, and condensed matter physics. Such interdisciplinary training is become increasingly important in government and industrial research laboratories.