Oscillatory Flow Birefringence of Polymer Molecules in Dilute Solutions

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Abstract
A theory for the behavior of dilute solutions of polymer molecules in oscillatory shear has been given by Zimm. Two variable parameters are contained in the theory, these being the number of statistical chain segments which are joined by bead joints and the degree of hydrodynamic interaction between the beads of the chain model. While previous experimental evaluations of the theory as applied to viscoelasticity have been restricted to the case of an infinite number of segments, the results obtained from oscillatory flow birefringence measurements show that a finite number of segments is essential to describing the behavior of the polymer. The analysis of birefringence measurements in terms of the Zimm theory yields values for the longest relaxation time τ1, the number of segments N, the reduction function aT, and the optical factor q′ characteristic of the subchain as well as the temperature dependence of the friction factor. Both oscillatory and steady‐flow birefringence measurements for polystyrene S111 in Aroclor 1248 are compared with the theory for frequency and temperature dependence. For the solution tested, N lies between 40 and 100, τ1 is 0.00187 sec and the temperature dependence of the friction factor is approximately that of the solvent viscosity.