Interaction of main chain cationic polyelectrolyte with sodium dodecyl sulfate

The interaction of x,gamma -ionene (x = 2,4,6; gamma = 4,6,12) polycations with sodium dodecyl sulfate (SDS) has been investigated in aqueous solution . It was found that there is a narrow molar ratio of SDS/cation (similar to 1.0-1.35) depending on different ionenes, at which the viscosity of ionene- SDS aqueous solution rises suddenly due to the formation of water soluble i nter-polymer aggregates via the SDS attached on the polymer chains. The vis cosity falls sharply with further addition of excessive SDS, which forms mi celle in solution and causes the de-aggregation of the inter-polymer aggreg ates. The x, gamma values of the ionene, the polymer concentration and the SDS/cation ratio play a key role in determining the viscosity behavior. At the higher concentration of ionene a gelation occurs suddenly from solution at a specific molar ratio of SDS/cation and was confirmed to be reversible . The viscosity increase and gel formation in ionene-SDS aqueous solution w ere considered to be related closely with presence of the hydrophobic domai n. Using N,N-dimethylflavon as fluorescent probe, the existence of hydropho bic domain in solution has been verified, the hydrodynamic radius of the ag gregates in the viscose solution was determined with laser light scattering and an explanation for the viscosity change as well as the gel formation h as been proposed. (C) 2001 Elsevier Science Ltd. All rights reserved.