title: Role of microscopic phase separation in gelation of aqueous gelatin solutions.
abstract: Using a unique home-made cell for four-contact impedance spectroscopy of conductive liquid samples, we establish the existence of two low frequency conductivity relaxations in aqueous solutions of gelatin, in both liquid and gel states. A comparison with diffusion measurements using pulsed field gradient NMR, and circular dichroism spectroscopy, shows that the faster relaxation process is due to gelatin macromolecule self-diffusion. This single molecule diffusion is mostly insensitive to the macroscopic state of the sample, implying that we have a clear separation of gelatin molecules into a free and network-bound phase. Scaling relationships for the self-diffusion indicate that the gelation process is not a percolative phenomenon, but is caused by aggregation of triple helices into a system-spanning fibre network.
authors.affiliation: Department of Physics, Faculty of Science, University of Zagreb, Bijenička 32, 10000 Zagreb, Croatia. basletic@phy.hr.
authors.forename: Damjan
authors.initials: D
authors.lastname: Pelc
authors.forename: Sanjin
authors.initials: S
authors.lastname: Marion
authors.forename: Miroslav
authors.initials: M
authors.lastname: Požek
authors.forename: Mario
authors.initials: M
authors.lastname: Basletić
mesh_terms: D058266:Dielectric Spectroscopy; D004058:Diffusion; D005780:Gelatin / Q000737:chemistry*; D005782:Gels / Q000737:chemistry; D012996:Solutions; D014867:Water / Q000737:chemistry
chemical_list: D005782:Gels; D012996:Solutions; D014867:Water; D005780:Gelatin