Hydrophobic Pockets in a Nonpolymeric Aqueous Gel: Observation of such a Gelation Process by Color Change

摘要

Studies on aqueous and organogels derived from low molecular mass species have been of considerable interest in recent years because of the many potential applications envisaged.[1] While gel formation in aqueous and nonaqueous media by polymers and biopolymers is a well-documented phenomenon,[2] detailed study of low molecular mass gelators has been embarked upon only during the past decade. Recently published examples of small molecule organogelators include steroids,[3] carbohydrates,[4] anthryl derivatives,[5] and urea.[6] We recently reported the first example of the gelation of organic fluids that was promoted by a donor acceptor interaction.[7] Although there is a resurgence in the study of low molecular mass organogelators, there is little activity in the investigation of analogous hydrogelators.[8]Herein we report that a novel tripodal[9] cholic acid derivative 1 forms gels in aqueous media with remarkable efficiency, and that the gelation process creates highly hydrophobic pockets in a predominantly aqueous environment. We have also demonstrated for the first time the sol to gel transition for a nonpolymeric gel by a color change.