A spectroscopic study of polyelectrolyte solutions under shear

The chain segment orientation of the polyelectrolyte poly(styrene sulfonate ), PSS, in glycerol solutions under shear have been studied using a novel U ltra Violet rheo-optic technique. The extinction coefficient of the polyele ctrolyte in solution, E, was measured using unpolarised light perpendicular to the direction of flow and is shown to decrease upon the application of shear. When the incident light was polarised with the direction of shear th e reduced change in extinction coefficient of the polyelectrolyte became mo re negative with shear. For light polarised perpendicular to the shear dire ction the reduced change in extinction coefficient of the polyelectrolyte i ncreased, became more positive, with the application of shear. There was no shear-induced change in the reduced change in extinction coefficient of th e polyelectrolyte backbone for light polarised at 67 degrees to the directi on of shear. All shear-spectroscopic behaviour may be explained by the alig nment of the polarised PSS monomer units in the direction of shear. The max imum dichroic ratio for the polyelectrolyte chain is related to the chain p olarisability and was predicted from the angular dependence of the change i n extinction measurements to be approximately 2.35. Crown Copyright (C) 200 1 Published by Elsevier Science Ltd. All rights reserved.