Coil Deformation, Scattering, and Fracture During Flow of Dilute Polymer Solutions

“强”流场可使长的柔性聚合物的通常卷曲构象基本上变形。 这项调查将使用激光散射来测量溶解在流动溶剂中的稀聚合物链（MW 1000万）的分子变形。实验将集中在反对射流和孔流，几何形状的流场最接近单轴伸长。 将系统地调整表征链、溶剂和流动强度的变量，以测试文献中的聚合物/流动模型。 当骨架中的流动诱导张力变得足够大时，链断裂，产生两个可能不相等分子量的片段链。 碎片分布的宽度反映了断裂瞬间的链构象。 凝胶电泳将被用来检查在各种稳定和瞬态层流能够链变形和断裂产生的分布。 湍流减阻通常被解释为使用聚合物/流动模型，预先假定全链延伸;减阻流中产生的链片段的研究将允许测试这一假设。 在几乎每一种聚合物溶液的应用或环境中都观察到了流动诱导的分子变形和链断裂。通过对聚合物/流动相互作用，特别是流动诱导的链延伸的深入了解，可以获得以下聚合物技术：本体拉伸流动性能的控制和稳定（食品、涂料）、过滤和在多孔基质中加工（生物聚合物操作、石油回收）、滑动表面润滑（记忆装置、机油）和溶液纺丝（天然蛋白质的流动诱导结晶、高模量纤维的制备）。

9416955 Hoagland A "strong" flow field can substantially deform the usual coiled conformation of a long flexible polymer. This investigation will use laser light scattering to measure the molecular deformation of dilute polymer chains (MW10 million) dissolved in a flowing solvent. Experiments will focus on opposed jets and orifice flows, geometries where the flow field best approximates uniaxial elongation. Variables characterizing the chain, solvent, and flow strength will be adjusted systematically to test polymer/flow models from the literature. When flow-induced tension in the backbone becomes sufficiently large, the chain breaks, generating two fragment chains of potentially unequel molecular weight. The breadth of the fragment distribution reflects the chain conformation at the instant of fracture. Gel electrophoresis will be employed to examine the distributions produced in various steady and transient laminar flows capable of chain deformation and fracture. Turbulent drag reduction has often been explained using polymer/flow models that presuppose full chain extension; a study of chain fragments created in drag reducing flow will allow this hypothesis to be tested. %%% Flow-induced molecular deformation and chain fracture have been observed in nearly every application or environment where polymer solutions are found. A list of polymer technologies that would benefit from an improved understanding of polymer/flow interaction, and especially of flow-induced chain extension, includes the following: control and stabilization of bulk elongational flow properties (foods, coatings), filtration and processing in porous matrices (biopolymer manipulation, oil recovery), lubrication of sliding surfaces (memory devices, motor oils), and solution spinning (flow-induced crystallization of natural proteins, preparation of high modulus fibers).