Solution behavior of progressively quaternized poly(dimethylaminoethyl methacrylate) as a function of charge density

Hydrodynamic behavior of progressively quaternized poly(dimethylaminoethyl methacrylate) (PDMAEM) in dilute and semi-dilute salt-free aqueous solutions as a function of molar mass and charge density, which varied from 5 up to 100 mol%, was studied. The role of long range electrostatic interactions on the viscosity and on the position and value of the reduced viscosity corresponding to the peak, ηred,p, as a function of the charge density of polycation has been evaluated. The overlap concentration of polyelectrolytes, c∗, has been evaluated as the inverse of the intrinsic viscosity determined by fitting the viscometric results on Rao equation. The values of c∗ have been discussed as a function of polyion molar mass and charge density. The c∗ values calculated in the frame of Odijk model for polyelectrolytes having quaternization degree ⩾50 were lower but comparable with those determined by viscometry, for the same molar mass.