INFINITE-DILUTION OSCILLATORY FLOW BIREFRINGENCE PROPERTIES OF POLYSTYRENE AND POLY( alpha -METHYLSTYRENE) SOLUTIONS.

In the reported experiments, oscillatory flow birefringence (OFB) measurements have been carried out for an extensive series of solutions containing narrow-distribution, atactic, linear polystyrenes PS (10,000 or 390,000 M// omega ) or poly ( alpha -methylstyrene) PMS (400,000 M// omega ) in a high-viscosity solvent, Aroclor 1248. The concentration ranges examined are such that the concentration dependence is obtained in both the ″dilute″ and ″semidilute″ regimes; the data are sufficiently precise to permit extrapolation to obtain for the first time the infinite-dilution properties. Various plotting formats are explored to determine an appropriate extrapolation procedure. The infinite-dilution OFB properties are compared with the bead-spring model (Zimm) theory which predicts quantitatively the frequency dependence of the observed properties for the PS and PMS solutions studied except for the high-frequency regime. The sensitivity and precision of the OFB experiment is such that the extrapolation curves - and the resulting infinite-dilution properties - show substantially less scatter than comparable viscoelasticity (VE) data.