Non‐newtonian flow of dilute macromolecular solutions studied by capillary viscometry

This paper reviews recent work on the flow behaviour of some typical polymers (cellulose nitrate, sodium carboxymethyl cellulose and polystyrene) at high dilution. The present experiments have been performed in the gradient range 0.5–150,000 sec −1 . The ratio [η] ∞ /[η] 0 ([η] ∞ being obtained by hyperbolic extrapolation) decreases with the expansion of the macromolecular coil but is independent of the viscosity of the solvent (η 0 ). All the [η] vs. shear rate curves show a finite initial slope, which increases with η 0 and molecular weight (M), rigidity, and expansion of the macromolecular coil. For cellulose nitrate the inner viscosity constant η i = const. M −1 η 0 0 while the relative flexibility increases with M and η 0 . The experimental results are viewed in the light of theories by C ERF , Č OPIČ , K UHN , and P ETERLIN .