Viscosity and longest relaxation time of semi-dilute polymer solutions. I. Good solvent

The zero shear viscosity and longest relaxation time are measured for semi-dilute polystyrene benzene solutions. For monomer concentrations c smaller than 10% and over a large range of the reduced concentration c/c* where c* is the overlap concentration (4 < c/c* < 70), we find that : — both the relative viscosity ηr and the longest relaxation time T R divided by the first mode characteristic time T1 of a single chain are function of the reduced concentration c/c* only; — the shear elastic modulus is independent of the molecular weight These results are in agreement with theoretical predictions. We find that η and TR depend on the reduced concentration and the molecular weight as follows : However, we find that X c is an increasing function of c/c* and that XM increases with c. This cannot be explained using the simple reptation model.