Interaction of mono-carboxylic acids in benzene studied by small-angle neutron scattering

The intermolecular interaction of non-saturated (oleic acid) and saturated (stearic and myristic acids) mono-carboxylic acids in a non-polar organic solvent (deuterated benzene) is derived from the concentration dependence of the small-angle neutron scattering. The excluded volume repulsion dominates over the attraction (supposed due to van der Waals forces) for oleic and myristic acids. In turn, for stearic acid the attractive component is higher than the repulsive one; this results in a shift of the transition into the liquid crystalline state (because of molecule anisotropy) towards smaller concentrations and could explain early data on worse stabilization properties of stearic acid in ferrofluids compared to oleic and myristic acids.