INTERACTIONS OF IONIC SURFACTANTS WITH GELATIN IN FLUID SOLUTIONS AND THE GEL STATE STUDIED BY FLUORESCENCE TECHNIQUES, POTENTIOMETRY, AND MEASUREMENTS OF VISCOSITY AND GEL STRENGTH

The photobehavior of pyrene (fine structure of the monomeric fluorescence band; excited state lifetimes; excimer/monomeric fluorescence intensity ratios and excited state quenching rates by oxygen) in fluid solutions of gelatin and in the gel state, both in the absence and presence of ionic surfactants, has been examined. Surfactants considered were sodium dodecylsulfate and dodecyltrimethylammonium bromide. Potentiometric measurements performed by using surfactant selective electrodes allowed for the determination of the binding capacity of the surfactants onto gelatin in the gel state. When complemented with viscosity and gel strength measurements, the results obtained allow for a discussion of the effects of the surfactant-gelatin interactions on microscopic properties of the solutions or gels and their relation with macroscopic properties.