Scattering Studies of Polymer Deformation in Flowing Solutions

当聚合物流体流动时，单独的聚合物链可以变成 因流体动力而变形。 理解这种变形 工艺是聚合物流变学的中心研究目标， 单个链的构象动力学最终产生 非牛顿流动特性。 尽管这一重要性显而易见， 很少有人尝试直接研究高分子链 流动中的动力学 在这个项目中，低角光散射是 用于探测聚合物的拉伸和取向， 稀溶液的稳定单轴拉伸流动。 结果 从上一个资金周期表明， 在模型流中的拉伸，在相对的射流之间产生， 与先前通过间接光学方法所建议的一样大 （双折射）或当前的分子理论。 物理 负责控制变形速率的机制 和柔性聚合物的最终变形水平 通过改变分子量、溶剂类型和 质量、伸长率和骨架刚度。 实验 在最近完成的光散射实验中 一种能够低角度测量极高 位于停滞点的小散射体积。 这些 测量将通过双折射研究进行补充， 在更瞬态的应力环境中进行流动实验。 本研究旨在了解大分子在流动中的行为， 它具有重要的科学意义， 技术，如纤维纺丝，减阻， 提高石油采收率

When polymeric fluids flow, individual polymer chains may become deformed by hydrodynamic forces. Understanding this deformation process is a central research goal of polymer rheology, as the conformational dynamics of individual chains ultimately create non-Newtonian flow properties. Despite this obvious importance, few attempts have been made to study directly polymer chain dynamics in flow. In this project, low-angle light scattering is used to probe the stretching and orientation of polymers in steady uniaxial elongational flow of dilute solutions. Results from the previous funding period indicate that the level of chain stretching in a model flow, created between opposed jets, may not be as great as previously suggested by indirect optical methods (birefringence) or current molecular theories. The physical mechanisms responsible for controlling the rate of deformation and the ultimate deformation level of flexible polymers are now being examined by varying molecular weight, solvent type and quality, elongation rate, and backbone stiffness. Experiments are being conducted in a recently completed light-scattering apparatus capable of low-angle measurements off an extremely small scattering volume located at a stagnation point. These measurements will be complemented by birefringence studies and flow experiments in more transient stress environments. This research aims to understand macromolecular behavior in flow, which is of fundamental scientific importance as well as in technology, such as fiber spinning, turbulent-drag reduction, and enhanced oil recovery.