title: Self-assembly of ketals of arjunolic acid into vesicles and fibers yielding gel-like dispersions.
abstract: Ten aliphatic and aromatic ketals of arjunolic acid, a renewable, nanosized triterpenic acid which is obtainable from Terminalia arjuna, have been synthesized upon condensation with aldehydes. Self-assembly properties of the ketals have been studied in a wide range of organic liquids. With the exception of the p-nitrobenzylidene derivative, low concentrations of the ketals self-assemble and form gel-like dispersions in many of the organic liquids examined. The morphologies of the assemblies, studied at different distance scales by optical, electron, and atomic-force microscopies, consisted of fibrillar networks and vesicles which were able to entrap 5(6)-carboxyfluorescein as a guest molecule. X-ray diffractograms indicate that the fibrillar objects are crystalline. A charge-transfer complex was formed from a 1:1 mixture of ketal derivatives with electron-donating and electron-accepting groups, and the 9-anthrylidene derivative in its fibrillar network dimerized upon irradiation. Results demonstrate that subtle changes in the ketal structures can lead to very different aggregation pathways.
authors.affiliation: Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore 721 102, WB, India. braja@mail.vidyasagar.ac.in
authors.forename: Braja G
authors.initials: BG
authors.lastname: Bag
authors.forename: Rakhi
authors.initials: R
authors.lastname: Majumdar
authors.forename: Shaishab K
authors.initials: SK
authors.lastname: Dinda
authors.forename: Partha P
authors.initials: PP
authors.lastname: Dey
authors.forename: Gopal C
authors.initials: GC
authors.lastname: Maity
authors.forename: V Ajay
authors.initials: VA
authors.lastname: Mallia
authors.forename: Richard G
authors.initials: RG
authors.lastname: Weiss