IONIC-STRENGTH EFFECTS IN AQUEOUS-SOLUTIONS OF GELATIN AND SODIUM DODECYL-SULFATE

The interaction between the anionic surfactant sodium dodecylsulphate and the polyampholyte gelatin in aqueous solution has been studied by viscosity and fluorescence, Three different gelatin molecular weights, a polydisperse gelatin and two fractionated samples derived from it, have been examined at two ionic strengths. On addition of sodium dodec ylsulphate SDS, the viscosity of a low molecular weight fractionated ( alpha) gelatin increases smoothly with SDS concentration, unlike the p olydisperse (standard) and high molecular weight (HMW) fractionated ge latins which show maxima. The viscosity increase at the maximum increa ses with gelatin molecular weight. On addition of 0.1 M salt, the visc osities of the gelatin-surfactant mixtures are lower than the equivale nt no-salt cases. Fluorescence studies suggest that the SDS micelles a dsorbed onto these various gelatins under two different ionic strength s are remarkably similar.