Diffusion of solutes in highly concentrated vesicle solutions from cationic surfactants: effects of chain saturation and ester function

Transport of water molecules across vesicle bilayers has been measured by NMR diffusometry. When changing the chemical structure of the surfactant differences in rate of water transport is observed. When comparing a hydrogenated dialkyl ester quat with the corresponding soft dialkyl ester quat a remarkable difference in the amount of transported water molecules over the bilayer is found. Below the transition temperature the hydrogenated dialkyl ester quat hinder water molecules from diffusing over the bilayer. The unsaturated version of the same molecule, however, cannot. Even far below the transition temperature a significant amount of water leaks during the observation times possible to study with the NMR diffusometry method. Above the transition temperature the hydrogenated dialkyl ester quat vesicle starts to leak water and the rate increase as the temperature increase.