Scattering of A Crystalline Gel Network: A New Organogel Based Upon A Benzohydroxamic Acid Derivative

A new aromatic gelator, p-octylbenzohydroxamic acid (OBHA), forms thermoreversible networks for concentrations as low as ca. 0.1% in several organic liquids. in the context of organogelators, the OBHA originality consists of a chemical structure that combines aromaticity with hydroxyl and amine groups. Preliminary rheology studies qualify the system as a viscoelastic solid and characterize the gel to sol melting transition. The small-angle scattering techniques (X-rays and neutrons) are used to investigate the structural features of the aggregates and their junction zones in the network. OBHA molecules are associated through hydrogen bonds in reverse configuration within long and rigid fibers with circular (r approximate to 58 Angstrom) or slightly rectangular (ca. 70 x 150 Angstrom) cross sections. A large-angle Bragg peak (spacing of 34.3 Angstrom) characterizes the crystallinity of the network organized through bimolecular associations. The low-angle scattering of such crystalline gels can be described using the Debye-Bueche model assuming a random distribution of the heterogeneities in the network. Scattering data suggest the existence of a concentration-dependent growth process of lamellar-like junction zones.