Short chain alcohols are used in numerous applications such as drug delivery, detergency and EOR involving ionic and nonionic surfactants. Commonly used as a “co-surfactant” or “co-solvent”, short chain alcohols like methanol to butanol can act in some ways like a surfactant, adsorbing to interfaces and lowering surface tensions. Unlike surfactants, these molecules cannot form micelles but interestingly can self-associate in water based on the hydrophobicity of the alcohol. When used in conjunction with various surfactants, changes in formulation phase behavior and notable properties such as oil solubilization have been observed. In order to further understand the effects of such alcohols on formulation behavior, we employed the Hydrophilic Lipophilic Deviation (HLD) model in order to quantify the changes in formulation HLD parameters, K and Cc, as a function of alcohol concentration. Preliminary results for two reference surfactants have confirmed previous work done by the Salager group and imply that there exists a minimum hydrophobe size (n-propyl alkyl) in order to interact within the palisade layer. Further, by following Ostwald’s logic of molar properties we propose a modification to the HLD f(A) term where the additive properties of the alcohol such as its size (molecular weight) and hydration can predict the effect on the formulation HLD. This modification conveniently returns HLD to a colligative equation in which the changes of surfactant chemical activity is only a function of solute concentration (in g/100ml) and temperature.
