Critical polymer concentration in highly diluted solutions

Polymer solutions exhibit a critical concentration, c**, separating the ran ge of dilute solution of the extremely diluted ones. Using viscosity measur ements, we have put into evidence this critical concentration for both flex ible and rigid polymer chains. The critical concentration depends on the sh ear rate, the nature of the solvent and the molecular weight. The phenomeno n can be explained by the influence of the shear forces on the radius of gy ration of the macromolecular coil. (C) 2000 Elsevier Science Ltd. All right s reserved.