Scattering Studies of Polymer Deformation in Flowing Solutions

流动溶液中聚合物变形的散射研究

• 批准号: 9019527
• 负责人: David Hoagland
• 金额: $ 21.99万
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1991
• 资助国家: 美国
• 起止时间: 1991-03-01 至 1994-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9019527&HistoricalAwards=false
• 关键词: Scattering; Studies; Polymer; Deformation; Flowing

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.

当聚合物流体流动时，单个聚合物链可能会因流体动力而变形。了解这种变形过程是聚合物流变学的中心研究目标，因为单链的构象动力学最终产生了非牛顿流动特性。尽管有这一明显的重要性，但很少有人尝试直接研究流动中的高分子链动力学。在本项目中，使用小角度光散射来探测聚合物在稳定的单轴拉伸稀溶液流动中的拉伸和取向。来自前一个资助期的结果表明，在相反的喷嘴之间产生的模型流中的链伸展水平可能不像以前通过间接光学方法(双折射)或当前的分子理论所暗示的那样大。控制柔性聚合物变形速度和最终变形水平的物理机制现在正在通过改变分子量、溶剂类型和质量、延伸率和主干硬度来检验。实验正在最近完成的光散射装置中进行，该装置能够对位于停滞点的极小散射体进行小角度测量。这些测量将得到双折射研究和更多瞬时应力环境中的流动实验的补充。这项研究旨在了解大分子在流动中的行为，这在纤维纺丝、湍流减阻和提高石油采收率等技术上具有基础性的科学意义。