title: Universal behaviour of gel formation from acrylamide-carrageenan mixture around the gel point: a fluorescence study.
abstract: The steady state fluorescence (SSF) technique was used to study the sol-gel transition, for the solution free radical crosslinking copolymerization of acrylamide (AAm) with various carrageenan content. N, N'- methylenebis (acrylamide) (BIS) and ammonium persulfate (APS) are used as crosslinker and an initiator, respectively. Pyranine (8-hydroxypyrene-1, 3,6-trisulfonic acid, trisodium salt, HPTS) was added as a floroprobe for monitoring the polymerization. Pyranine molecules start to bind to acrylamide polymer chains upon the initiation of the polymerization; thus, the spectra of the bonded pyranines shift to the shorter wavelengths. Fluorescence spectra from the bonded pyranines allows one to monitor the sol-gel transition, without disturbing the system mechanically, and to test the universality of the sol-gel transition as a function of some kinetic parameters like polymer concentration. Observations around the critical point show that the gel fraction exponent beta obeyed the percolation result for low carrageenan concentrations (< 2.0%) however classical results were produced at higher carrageenan concentration (> 2.0%).
authors.affiliation: Istanbul Technical University, Department of Physics, 34469 Maslak Istanbul Turkey. demet@itu.edu.tr.
authors.forename: Demet Kaya
authors.initials: DK
authors.lastname: Aktas
authors.forename: Gülşen Akin
authors.initials: GA
authors.lastname: Evingur
authors.forename: Onder
authors.initials: O
authors.lastname: Pekcan
mesh_terms: D020106:Acrylamide / Q000737:chemistry*; D001190:Arylsulfonates / Q000737:chemistry; D002351:Carrageenan / Q000737:chemistry*; D005782:Gels; D013050:Spectrometry, Fluorescence / Q000706:statistics & numerical data
chemical_list: D001190:Arylsulfonates; D005782:Gels; D020106:Acrylamide; D002351:Carrageenan; C005047:pyranine