Polymer-Surfactant Interactions: The Gelatin-SDS Example

Binding of the anionic surfactant, sodium dodecyl sulfate, SDS to gelatin chains in aqueous buffer (pH = 7.0) medium has been studied by dynamic light scattering technique at 30°C. In the surfactant concentration range varying from 0 to 100 mM, SDS exhibited electrostatic binding to the charged groups of the polypeptide chain resulting in considerable reduction in the hydrodynamic radius (R_h) of gelatin upto the critical aggregation concentration (CAC); at higher concentrations both the SDS micelles and gelatin-SDS complexes were found to coexist in equilibrium. The micellar shapes were found to be near-spherical for SDS. Results have been interpreted through the necklace-bead model of polymer-surfactant interactions.