SCATTERING OF A CRYSTALLINE GEL NETWORK - A NEW ORGANOGEL BASED UPON A BENZOHYDROXAMIC ACID-DERIVATIVE

A new aromatic gelator, p-octylbenzohydroxamic acid (OBHA), forms ther moreversible networks for concentrations as low as ca. 0.1% in several organic liquids. in the context of organogelators, the OBHA originali ty consists of a chemical structure that combines aromaticity with hyd roxyl and amine groups. Preliminary rheology studies qualify the syste m as a viscoelastic solid and characterize the gel to sol melting tran sition. The small-angle scattering techniques (X-rays and neutrons) ar e used to investigate the structural features of the aggregates and th eir junction zones in the network. OBHA molecules are associated throu gh hydrogen bonds in reverse configuration within long and rigid fiber s with circular (r approximate to 58 Angstrom) or slightly rectangular (ca. 70 x 150 Angstrom) cross sections. A large-angle Bragg peak (spa cing of 34.3 Angstrom) characterizes the crystallinity of the network organized through bimolecular associations. The low-angle scattering o f 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 gro wth process of lamellar-like junction zones.