title: Reversible phase transitions within self-assembled fibrillar networks of (R)-18-(n-alkylamino)octadecan-7-ols in their carbon tetrachloride gels.
abstract: The CCl(4) gel phases of a series of low-molecular-mass organogelators, (R)-18-(n-alkylamino)octadecan-7-ols (HSN-n, where n = 0-5, 18 is the alkyl chain length), appear to be unprecedented in that the fibrillar networks of some of the homologues undergo thermally reversible, gel-to-gel phase transitions, and some of those transitions are evident as opaque-transparent changes in the appearance of the samples. The gels have been examined at different concentrations and temperatures by a wide variety of spectroscopic, diffraction, thermal, and rheological techniques. Analyses of those data and data from the neat gelators have led to an understanding of the source of the gel-to-gel transitions. IR and SANS data implicate the expulsion (on heating the lower-temperature gel) or the inclusion (on cooling the higher-temperature gel) of molecules of CCl(4) that are interspersed between fibers in bundles. However, the root cause of the transitions is a consequence of changes in the molecular packing of the HSN-n within the fibers. This study offers opportunities to design new gelators that are capable of behaving in multiple fashions without entering the sol/solution phase, and it identifies a heretofore unknown transformation of organogels.
authors: Department of Chemistry, Georgetown University, Washington, DC 20057-1227, United States.
authors: V Ajay
authors: VA
authors: Mallia
authors: Paul D
authors: PD
authors: Butler
authors: Bijay
authors: B
authors: Sarkar
authors: K Travis
authors: KT
authors: Holman
authors: Richard G
authors: RG
authors: Weiss
mesh_terms: D002251:Carbon Tetrachloride / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005233:Fatty Alcohols / Q000138:chemical synthesis / Q000737:chemistry*; D005782:Gels / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D044367:Phase Transition; D013237:Stereoisomerism
chemical_list: D005233:Fatty Alcohols; D005782:Gels; D002251:Carbon Tetrachloride