title: Structure and dynamics of a molecular hydrogel derived from a tripodal cholamide.
abstract: Tripodal cholamide 1 is a supergelator of aqueous fluids. A variety of physical techniques, including cryo-transmission electron microscopy (TEM), circular dichroism (CD), steady-state fluorescence, time-resolved fluorescence, and dynamic light-scattering, were employed to understand the structure and dynamics of the gel. Fluorescent probes [ANS (8-anilinonaphthalene-1-sulfonic acid) and pyrene] reported two critical aggregation concentrations (CAC(1) and CAC(2)) of 1 in predominantly aqueous media, with the minimum gel concentration (MGC) being close to CAC(2). Fluorescence lifetime measurements with pyrene revealed ineffective quenching of pyrene fluorescence by oxygen, possibly caused by slower Brownian diffusion due to the enhanced viscosity in the gel phase. The study of the gelation kinetics by monitoring the ultrafast dynamics of ANS revealed a progressive increase in the aggregate size and the microviscosity of the aqueous pool encompassed by the self-assembled fibrillar network (SAFIN) during the gelation. The striking difference between microviscosity and bulk (macroscopic) viscosity of the gel is also discussed.
authors.affiliation: Department of Organic Chemistry, Indian Institute of Science, Bangalore 560 012 India.
authors.forename: Samrat
authors.initials: S
authors.lastname: Mukhopadhyay
authors.forename: Uday
authors.initials: U
authors.lastname: Maitra
authors.forename: Ira
authors.initials: I
authors.lastname: Ira
authors.forename: Guruswamy
authors.initials: G
authors.lastname: Krishnamoorthy
authors.forename: Judith
authors.initials: J
authors.lastname: Schmidt
authors.forename: Yeshayahu
authors.initials: Y
authors.lastname: Talmon
mesh_terms: D000577:Amides / Q000737:chemistry*; D002793:Cholic Acids / Q000737:chemistry*; D002942:Circular Dichroism; D005454:Fluorescence Polarization; D020100:Hydrogels / Q000737:chemistry*; D008027:Light; D046529:Microscopy, Electron, Transmission; D011721:Pyrenes / Q000737:chemistry; D012542:Scattering, Radiation; D013050:Spectrometry, Fluorescence; D014867:Water / Q000737:chemistry
chemical_list: D000577:Amides; D002793:Cholic Acids; D020100:Hydrogels; D011721:Pyrenes; D014867:Water; C030984:pyrene