The concentration-dependence of the reduced viscosity of dilute polymer solution is interpreted in the light of the self-association concept of polymer chain in solution. The molar selfassociation constant (Ka) is directly proportional to the effective hydrodynamic volume of the polymer chain in solution. In the sense of self-association or cluster formation of polymer chain in solution, there is no difference between branched and linear polymers.
The measured reduced viscosity\|concentration ( η \-\{sp\}/ c\|c ) curves of miscible PPO/PS、 immiscible PMMA/PS mixtures with different composition in toluene all deviate from linear and reveal downward turn in extremely dilute concentration region. Moreover, in the extremely dilute concentration region, the η \-\{sp\}/ c\|c curve of immiscible PVC/PS mixture solution shows upward turn in THF, while shows downward turn in DCE. These experimental facts indicate that such viscosity anomaly is not dependent of miscibility, but resulted from wall effects. Regarding the polymer mixture as a single solute, the interference of wall effects on viscosity measurement could be eliminated quantitatively with a proposed theoretical formula. After corrected, the true viscosity data of mixture shows normal linear η\-\{s p\}/ c\|c curve in the dilute and extremely dilute concentration region.
