Dynamics of Multicomponent Polymer Liquids

本研究旨在开发和应用光学流变学方法来测量多组分聚合物液体在加工条件下的动力学和结构。这种液体的特征是与特定的结构成分相关的动力学，应该分离这些成分以适当地了解这些材料对外场的响应。这种分离可以指作为液体中存在的或与特定化学成分相关的长度尺度的函数的动力学的隔离。前一类系统将包括相分离的混合物，其中域结构的响应必须被隔离。对于这些情况和在0.5到20微米范围内的结构长度尺度，散射技术是显而易见的选择，为此将使用小角光散射和散射二向色性。当必须确定单个化学元素的动力学时，需要光谱技术。红外偏振和拉曼散射将被发展并应用于单相聚合物共混物和熔体。将开展的具体工作有：1.对于可混溶的单相混合物，重要的是要了解各组分的摩擦因数与组成和温度的关系。还需要一条额外的信息，即作为组成函数的缠结分子量。为了实现这些目标，红外二向色性和一种新技术--偏振调制拉曼散射--将被用于光谱识别特定的化学成分。2.)在剪切会影响多组分体系的相行为的系统中，将使用散射和光谱技术在大范围的结构长度尺度上检查结构。对于具有分散相的体系，将使用小角光散射来监测这些液滴的变形。这将在组成混合物的组分的粘度比不同的系统中进行。为了研究驱动混溶或相分离的相互作用，将开发一种新的技术，即二维拉曼散射。这种方法将提供测量组成样品的不同元素之间的取向相关性的能力。最后，准分子荧光将被开发为一种探测极小(10埃)长度尺度上相互作用的技术。这项研究由材料研究部的聚合物项目和化学和热力系统部门的流体、颗粒和液压系统项目共同支持。

This research is directed at the development and application of methods in optical rheometry to measure the dynamics and structures of multicomponent polymer liquids when subjected to processing conditions. Such liquids are characterized by dynamics associated with specific structural constituents that should be separated to properly understand the response of these materials to external fields. This separation can refer to the isolation of the dynamics as a function of length scales existing in the liquid, or associated with specific chemical components. The former class of systems would include phase-separated blends where the response of the domain structure must be isolated. Scattering techniques are the obvious choices for these cases and for structural length scales in the range of 0.5 to 20 um, small-angle light scattering and scattering dichroism will be used for this purpose. Spectroscopic techniques are required when the dynamics of individual chemical elements must be identified. Infrared polarimetry and Raman scattering will be developed and applied to single-phase polymer blends and melts. The specific tasks that will be carried out are: 1.) For miscible, single-phase blends, it is important to understand the composition and temperature dependence of the friction factors of the individual components. An additional piece of information that is required is the entanglement molecular weight as a function of composition. To address these goals, infrared dichroism and a new technique, polarization modulated Raman scattering, will be used to spectroscopically identify specific chemical constituents. 2.) In systems where shear can affect the phase behavior of a multicomponent system, both scattering and spectroscopic techniques will be used to examine the structure over a wide range of structural length scales. For systems with a dispersed phase, small-angle light scattering will be used to monitor the deformation of those droplets. This will be carried out for systems where the viscosity ratio of the components making up the mixtures is varied. To examine the interactions that drive miscibility or phase separation, a new technique, two-dimensional Raman scattering will be developed. This method will offer the capability of measuring orientation correlations between distinct elements comprising a sample. Finally, excimer fluorescence will be developed as a technique to probe interactions over extremely small (10 angstrom) length scales. This research is jointly supported by the Polymers Program in the Division of Materials Research and the Fluid, Particulate and Hydraulic Systems Program in the Division of Chemical and Thermal Systems.