Influence of Surfactant Concentration and Background Salt on Forced Dynamic Wetting and Dewetting

Forced wetting and dewetting of polymer surfaces in aqueous solutions containing cationic surfactant cetyltrimethylammonium bromide (CTAB) has been studied with a rotating cylinder half immersed in the solution: The receding contact angle decreases with faster withdrawing speeds.' This decrease is enhanced when adding CTAB. The addition of salt to the CTAB solution further enhances the effect but does not have a significant effect alone. We interpret this change in the dynamic contact angle with a surfactant induced Marangoni effect.