title: Small angle neutron scattering (SANS) studies on the structural evolution of pyromellitamide self-assembled gels.
abstract: The kinetics of aggregation of two pyromellitamide gelators, tetrabutyl- (C4) and tetrahexyl-pyromellitamide (C6), in deuterated cyclohexane has been investigated by small angle neutron scattering (SANS) for up to 6 days. The purpose of this study was to improve our understanding of how self-assembled gels are formed. Short-term (< 3 h) time scales revealed multiple phases with the data for the tetrabutylpyromellitamide C4, indicating one-dimensional stacking and aggregation corresponding to a multifiber braided cluster arrangement that is about 35 Å in diameter. The corresponding tetrahexylpyromellitamide C6 data suggest that the C6 also forms one-dimensional stacks but that these aggregate to a thicker multifiber braided cluster that has a diameter of about 62 Å. Over a longer period of time, the radius, persistence length, and contour length all continue to increase in 6 days after cooling. These data suggest that structural changes in self-assembled gels occur over a period exceeding several days and that fairly subtle changes in the structure (e.g., tail-length) can influence the packing of molecules in self-assembled gels on the single-to-few fiber bundle stage.
authors.affiliation: School of Chemistry and the Australian Centre for Nanomedicine, The University of New South Wales , Sydney, NSW 2052 Australia.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Jamieson
authors.forename: Katie W K
authors.initials: KW
authors.lastname: Tong
authors.forename: William A
authors.initials: WA
authors.lastname: Hamilton
authors.forename: Lilin
authors.initials: L
authors.lastname: He
authors.forename: Michael
authors.initials: M
authors.lastname: James
authors.forename: Pall
authors.initials: P
authors.lastname: Thordarson
mesh_terms: D000577:Amides / Q000737:chemistry*; D001565:Benzoates / Q000737:chemistry*; D005782:Gels; D008956:Models, Chemical; D033363:Neutron Diffraction; D053838:Scattering, Small Angle
chemical_list: D000577:Amides; D001565:Benzoates; D005782:Gels; C012018:pyromellitic acid