LIGHT-SCATTERING FROM DILUTE POLYMER-SOLUTIONS IN SHEAR-FLOW

A self-constructed laser light scattering photometer including a shear cell has been used to investigate the scattering behavior of polystyrene (M(W) = 10.3 X 10(6)) in the viscous solvent dioctyl phthalate (DOP) in shear flow. Only highly dilute solutions were used (c < 0.8/[eta]). Changes of the scattering intensity were detected, depending on shear rate, detection angle, and polymer concentration. The special feature of our instrument is its ability to detect the wattering intensity in the plane of flow as well as in several planes perpendicular to the flow plane (Zimm planes). From measurements in the flow plane, the orientation angle can be determined directly. Furthermore, by variation of the wavelength of the incident light and detection angle, all three main radii of the ellipsoidal gyration space of polymer coils in shear flow were determined. While the orientation angles obtained show at least qualitative coincidence with the dynamic theories of Rouse and Zimm, a large discrepancy between theoretical and experimental molecular deformation was observed. The maximum deformation ratio of the radius of gyration compared to quiescent solution was 1.5. We also noticed a pronounced dependence of the orientation angle and deformation ratio on concentration. Additionally, in the polymer-solvent system considered, a shear-induced phase separation was encountered.