| Abstract
| - The adsorption of dodecyl single chain surfactants with primary, secondary, tertiary, and quaternaryammonium headgroups at the muscovite mica basal plane−water interface has been investigated usinga flat plate streaming potential apparatus and atomic force microscopy (AFM). Both a hemi-micelleconcentration (HMC) and a point of zeta potential reversal (PZR) were observed as the surfactant adsorbedat the muscovite mica−water interface. The HMC and PZR were shifted to higher surfactant concentrationas the headgroup was changed from the primary to the quaternary ammonium group. AFM images ofsurfactant patches adsorbed at the mica−water interface indicate that the surfactant patch size becomessmaller and distributes more uniformly with change from the primary to quaternary ammonium headgroups.The hydrophobic force contribution of the hydrocarbon chain to the adsorption of the C12 surfactant,estimated by subtracting other contributions from the total adsorption free energy, was calculated todecrease as the headgroup was changed from the primary to the quaternary amine.
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