Interaction Between EPTAC-Modified Gelatin and Surfactants: Surface Tension and Conductivity Methods

Gelatin, one of the most valuable macromolecules and by-products of the leather industry, was modified by the addition of 2,3-epoxypropyl trimethyl ammonium chloride (EPTAC). The interaction between EPTAC-modified gelatin (EPTAC-gelatin) and cetyltrimethyl ammonium bromide (CTAB) or sodium dodecyl benzene sulfonate (SDBS) was studied by surface tension and conductivity methods. We found that EPTAC-gelatin adsorbed more CTAB than SDBS but the surface-tension-reducing capabilities of EPTAC-gelatin–CTAB and EPTAC-gelatin–SDBS were almost equal. The micellization process of CTAB was enthalpy-driven but that of SDBS was entropy-driven at low concentrations of EPTAC-gelatin and enthalpy-driven at high concentrations. Based on the analysis of EPTAC-gelatin–CTAB (SDBS) solution properties, interaction models of EPTAC-gelatin–CTAB (SDBS) were proposed.