UNIAXIAL AND BIAXIAL EXTENSIONAL VISCOSITY MEASUREMENTS OF DILUTE AND SEMI-DILUTE SOLUTIONS OF RIGID ROD POLYMERS

Effective uniaxial extensional and biaxial extensional viscosities of dilute and semi-dilute solutions of collagen, a rigid rod molecule, have been measured with an opposing jet apparatus. The concentration of collagen in the glycerin/water solvent ranged from 50 to 2300 pm. The data agree quantitatively with a theory developed by Batchelor describing the extensional viscosity of perfectly aligned rigid rods. The viscosity measured for the dilute rigid rods solutions is independent of the rate of strain as predicted by Batchelor's theory. Data taken on the semi-dilute, strain-thinning solutions at strain rates sufficiently high to align the rods in the extension direction also agree with the predictions of Batchelor's theory. The measured viscosity of semi-dilute solutions at low strain rates agree qualitatively with a theory, developed by Doi and Edwards, describing the strain-thinning behavior of semi-dilute rigid rod solutions.