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

“强”流场可以使长柔性聚合物通常的卷曲构象大幅度变形。本研究将使用激光散射来测量溶解在流动溶剂中的稀聚合物链（mw1000万）的分子变形。实验将集中在相对的射流和孔板流动，几何形状的流场最接近单轴延伸。表征链、溶剂和流动强度的变量将被系统地调整，以测试文献中的聚合物/流动模型。当流动引起的主链张力足够大时，链断裂，产生两个分子量可能不相等的片段链。碎片分布的宽度反映了断裂瞬间的链状构象。凝胶电泳将用于检查在各种稳定和瞬态层流中产生的分布，这些层流能够产生链变形和断裂。紊流阻力减少通常用聚合物/流动模型来解释，假设全链延伸；对在减阻流中产生的链碎片的研究将使这一假设得到检验。几乎在所有聚合物溶液的应用或环境中都可以观察到流动引起的分子变形和链断裂。如果能更好地理解聚合物与流体的相互作用，特别是流体引起的链延伸，将会有一系列聚合物技术从中受益，包括：控制和稳定大块拉伸流动特性（食品，涂料），多孔基质的过滤和加工（生物聚合物操作，石油回收），滑动表面的润滑（存储设备，机油），以及溶液纺丝（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).