NANOEMULSIONS OF POLYOXYETHYLENE(4) LAURYL ETHER WITH SOLUBILIZED CHLORHEXIDINE BASE

Abstract

Nanoemulsions (NEs) of simple compositions have been obtained, in which polyoxyethylene(4) lauryl ether (Brij L4, Br-4) plays the roles of a dispersed phase and a stabilizer, while water is a dispersion medium. The following properties of NEs have been studied: particle size distribution; solubilization capacity; and transport properties with respect to the lipophilic biocide, chlorhexidine (CH) base. The long-term aggregative stability of NEs (for several months) and the efficient mass transfer of CH by the NE dispersed phase particles in the aqueous medium have been confirmed. A unique phenomenon of a spontaneous decrease in the sizes of NE droplets upon solubilization of CH has been found, with the particle average diameter decreasing from 52 ± 6 to 19 ± 3 nm. The reason for this phenomenon is the formation of complexes between Br-4 and CH molecules on the surface of the droplets, with the complexes being better soluble in water than Br-4. Brij L4 molecules included into the complexes are transferred from the droplet surface into the dispersion medium, thus leading to the decrease in the droplet sizes. The complexation occurs due to the formation of multiple N⋅⋅⋅H⋅⋅⋅O hydrogen bonds. From 84 to 96% of the biocide solubilized in the NEs is also localized in the polyoxyethylated layer of Br-4 droplets due to H-bonds.