We employ a meanhyphen;field model for monolayers of shorthyphen;chain surfactants at an oilndash;water interface, and include a quantitative consideration of the headhyphen;group interactions (both steric and electrostatic) and the interfacial geometry. The behavior is then analyzed numerically, giving values for the spontaneous curvature, the bending moduli, and the neutral plane position, as the molecular parameters are varied. The spontaneous curvature is found to have a lsquo;lsquo;universalrsquo;rsquo; behavior for different type of head groups, which leads to a confirmation of the geometric theory of the surfactant parameter. The values for the bending moduli are consistent with experiments, and for the case of electrostatic head group interactions we predict thatkcis only weakly dependent on electrolyte concentration. The local continuum analysis of the bending energy of monolayers, on which other theories depend, is shown to be only valid close to the spontaneous curvature.
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