Infinite‐dilution oscillatory flow birefringence properties of polystyrene and poly(α‐methylstyrene) solutions

Abstract

AbstractOscillatory 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 Mw) or poly(α‐methylstyrene) PMS (400,000 Mw) 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 visco‐elasticity (VE) data. There is no evidence of a change in the character of the concentration dependence for the range of concentrations studied.