Presidential Young Investigator Award

这项总统青年研究员研究计划将沿着三条路线发展：研究聚合物混合热力学，评估聚合物-聚合物相分离和嵌段共聚物有序的动力学，建立模型材料的合成和表征设施。在热力学领域有两类主要的混合物：二元聚合物混合物和嵌段共聚物。研究工作的方向将是利用模型系统推进我们对聚合物段相互作用的理解，并将这些知识与实验确定的过量热力学性质、相图和界面现象联系起来。这些信息将通过中子、x射线和光散射方法，以及电子和光学显微镜技术获得。在动力学方面将启动两个项目：双聚合物混合物的旋多分解、成核和生长，以及嵌段共聚物中有序和无序的流变特性。这些研究利用我们的热力学结果来开发适当的相图，用相图来探索与相分离动力学有关的问题，以及所得材料的性质。同位素聚合物混合物是理想模型系统的一个例子，我们将用它来研究光和中子散射的旋多分解。嵌段共聚物动力学的研究将主要依靠机械光谱仪和小角x射线和中子散射的联合使用。实现这些热力学和动力学目标取决于操纵分子量、微观结构、同位素组成和模型聚合物链结构的能力。这一要求将通过阴离子聚合设施的发展，通过催化氢化和分子表征能力的增强来满足。因此，有关聚合物热力学和动力学的信息可以直接应用于材料优化。

This Presidential Young Investigator research program will be developed along three lines: investigation of the thermodynamics of polymer mixing, evaluation of the dynamics of polymer-polymer phase separation and block copolymer ordering, and establishment of a synthesis and characterization facility for the development of model materials. In the area of thermodynamics two classes of mixtures are of principal interest: binary polymer mixtures and block copolymers. Research efforts will be directed at advancing our understanding of polymer segment interactions using model systems, and at correlating this knowledge with experimentally determined excess thermodynamics properties, phase diagrams, and interfacial phenomena. Such information will be obtained using neutron, x-ray and light scattering methods, along with electron and optical microscopy techniques. Two projects will be initiated in the dynamics category: spinodal decomposition, and nucleation and growth of binary polymer mixtures, and rheological characterization of order and disorder in block copolymers. These investigations take advantage of our thermodynamic results in developing the appropriate phase diagrams with which to explore issues relating to the dynamics of phase separation, and the properties of the resulting materials. Isotopic polymer mixtures represent one example of an ideal model system which we will be using in study -ing spinodal decomposition by light and neutron scattering. Investigation of block copolymers dynamics will rely mainly on the combined use of a mechanical spectrometer and small-angle x- ray and neutron scattering. Achieving these thermodynamics and dynamics goals depend upon the ability to manipulate the molecular weight, microstructure, isotopic constitution, and chain architecture of model polymers. This requirement will be met through the development of an anionic polymerization facility, augmented by a catalytic hydrogenation and molecular characterization capability. Thus, information regarding polymer thermodynamics and dynamics can be applied directly to materials optimization.