In situ optical studies of flow-induced orientation in a two-dimensional polymer solution

The orientation dynamics of polymers in constrained geometries is considered through studies of monolayer films at the air-water interface. Here, in situ optical techniques are employed to probe flow orientation in monolayers of phthalocyaninatopolysiloxane dispersed in either docosanoic acid, 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine, or arachidyl alcohol. Compression of the polymer monolayer creates alignment perpendicular to the compression direction. A well-defined extensional flow is imposed in the monolayer to study the dynamics of flow-induced anisotropy. The orientation process obeys a strain-scaling law, indicating the absence of relaxation on the time scale of the flow.