title: New oil-gelling agents for cosmetics: formation mechanism of oil gels.
abstract: Summary New oil-gelling agents have been developed composed of a long-chain dialkyl phosphate (DP) surfactant and aluminium ion or multinuclear aluminum ion (MAI) which provide good oil-gel systems. One such gelling agent is the aluminum salt of DP (DP-Al) prepared as a precipitate by mixing DP with aluminum chloride in aqueous solutions. Addition of small amounts of the salt to non-polar oils led to hardening of the oil solutions at temperature below the melting point of the alkyl chain (Tc) of DP-Al. Results obtained by X-ray diffraction techniques and with scanning electron microscopy (SEM) revealed that linearly-polymerized assemblies of DP-Al expand in oils three-dimensionally, which suggests that the excellent stability of the gel systems arises from the highly ordered structure. The gelling agent of DP-Al offered the ideal rheological property to waxy cosmetic products such as lipsticks. The complexes of DP with MAI particles (1 nm diameter) of aluminum chlorohydrate, Al(13)O(4)(OH)(24)(H(2)O)(12)CI(7), provided the ideal thixotropic behaviour in non-polar oils. The DP-MAI particle complexes were found to interact weakly by cohesive forces which makes a highly ordered structure of the DP-MAI particle complexes. The DP-MAI particle complexes gave excellent stability and transparency to cosmetic products such as w/o creams.
authors.affiliation: Department of Chemistry, The University of North Carolina, NC 27599-3290, USA.
authors.forename: J
authors.initials: J
authors.lastname: Fukasawa
authors.forename: H
authors.initials: H
authors.lastname: Tsutsumi
authors.forename: A
authors.initials: A
authors.lastname: Ishida