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Kinetics of 5α-Cholestan-3β-yl N-(2-Naphthyl)carbamate/n-Alkane Organogel Formation and Its Influence on the Fibrillar Networks
journal contribution
posted on 2005-03-30, 00:00 authored by Xiao Huang, Pierre Terech, Srinivasa R. Raghavan, Richard G. WeissThe kinetics and mode of nucleation and growth of fibers by 5α-cholestan-3β-yl N-(2-naphthyl)carbamate (CNC), a low-molecular-mass organogelator (LMOG), in n-octane and n-dodecane have been
investigated as their sols were transformed isothermally to organogels. The kinetics has been followed in
detail by circular dichroism, fluorescence, small-angle neutron scattering, and rheological methods. When
treated according to Avrami theory, kinetic data from the four methods are self-consistent and describe a
gelation process involving one-dimensional growth and “instantaneous nucleation”. As expected from this
growth model, polarized optical micrographs of the self-assembled fibrillar networks (SAFINs) show fibrous
aggregates. However, their size and appearance change abruptly from spherulitic to rodlike as temperature
is increased. This morphological change is attended by corresponding excursions in static and kinetic CD,
fluorescence and rheological data. Furthermore, the rheological measurements reveal an unusual linear
increase in viscoelastic moduli in the initial stages of self-assembly. Each of the methods employed becomes
sensitive to changes of the system at different stages of the transformation from single molecules of the
LMOG to their eventual SAFINs. This study also provides a methodology for investigating aggregation
phenomena of some other self-assembling systems, including those of biological and physiological
importance.