AbstractThe hydrodynamic volume changes of the polyester‐based polyurethanes, as dimethylformamide solutions with and without lithium bromide, were studied. Gel‐permeation chromatographic (GPC) and intrinsic viscosity techniques were employed as methods for characterization. Decreases in intrinsic viscosity as well as dramatic changes in the GPC chromatograms were observed. These observations are explained by the polarity of these polyester‐based polyurethane molecules and the resulting characteristics of molecular expansion, association, and polymer–column interaction normally associated with polyelect