Abstract: Flow time data of aqueous polyvinylpyrrolidone-sodium dodecyl sulfate(PVP-SDS) complex solutions composed of different PVP mass concentrations (ρ_PVP) and SDS concentrations (c_SDS) were examined with Ubbelohde viscometer.Observation results showed that there exists double critical concentrations of SDS,c₁ and c₂ on the flow time plots of PVP-SDS solutions,which means SDS bound-micelles were associated in cluster on PVP chains.It was also found that the reduced specific viscosity (η_sp/ρ_PVP) of PVP-SDS solutions increases with the decrease of ρ_PVP evidently in lower ρ_PVP scope,which was different from the behavior of simple aqueous PVP solution but similar to the typical polyelectrolyte sodium polyacrylate solution.The mean square end-to-end distance r² and the relative expansion value k of PVP chains in the PVP-SDS cluster as compared with that of the simple PVP chains were calculated,and k values increases with the increase of specific clustered quantity [Г].Such an abnormal phenomenon in reduced specific viscosity curve was reasonably explained based on the calculation results and was attributed to the coil expansion of PVP chains caused by the charged SDS bound-micelles associated in cluster on PVP chains,which resulted in a unique effect on reduced specific viscosity similar to the “polyelectrolyte effect”.

Key words: sodium dodecyl sulfate, polyvinylpyrrolidone, reduced specific viscosity, polyelectrolyte effect, coil expansion