Measurements of viscoelastic properties of linear polymers in dilute and semidilute solutions with a flow birefringence method

To study viscoelastic properties of flexible macromolecules in dilute and semidilute solutions, a birefringence instrument with high sensitivity was constructed. A circularly polarized laser beam is used as an incident light, and the distortion of the beam by polymer molecules in shear flow was detected by a rotating half wave plate and photomultiplier and compensated with a Babinet-Soleil plate. The birefringence ∆n and extinction angle 훘 of polymer solutions can be measured simultaneously and independently. The steady-shear viscosity 훈 and steady-state compliance Je can be evaluated from observed values of ∆n and 훘 using a stress-optical law. The reliability of these data was confirmed by comparing the data with those determined by a Maron-Krieger-Sisko capillary viscometer and a Weissenberg rheogoniometer. The concentration dependence of reduced steady-state compliance J_eR of linear polystyrenes in bromobenzene (a matching solvent) in dilute and semidilute solutions are reported.