title: The role of pyranine in characterization of PAAm-κC composites by using fluorescence technique.
abstract: Polyacrylamide (PAAm) doped by κ-carrageenan (κC) gels were prepared with various amounts of κC varying in the range between 0 wt.% and 3 wt.%. Steady-state fluorescence (SSF) technique was employed for studying sol-gel transition and swelling of PAAm-κC composite gels which were prepared by free-radical crosslinking copolymerization. Pyranine was introduced as a fluorescence probe. 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 allow one to monitor the sol-gel transition and to test the universality of the sol-gel transition as a function of some kinetic parameters like polymer concentration. Observations around the gel point, t ( c ) for PAAm-κC composite gels showed that the gel fraction exponent β obeyed the percolation result for low κC (<2.0 wt. %) however classical results were produced at higher κC (>2.0 wt.%). On the other hand, fluorescence intensity of pyranine was measured during in situ swelling process at various amounts of κC and it was observed that fluorescence intensity values decreased as swelling is proceeded. Li-Tanaka equation was used to determine the swelling time constants, τ and cooperative diffusion coefficients, D.
authors.affiliation: Faculty of Science and Letters, Physics Department, Istanbul Technical University, 34469 Maslak- Istanbul, Turkey. evingur@itu.edu.tr
authors.forename: Gülşen Akin
authors.initials: GA
authors.lastname: Evingur
authors.forename: Önder
authors.initials: Ö
authors.lastname: Pekcan
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D001190:Arylsulfonates; D002351:Carrageenan / Q000737:chemistry*; D015335:Molecular Probes; D044367:Phase Transition; D058105:Polymerization; D013050:Spectrometry, Fluorescence / Q000379:methods*; D000099166:Polyacrylamides
chemical_list: D000180:Acrylic Resins; D001190:Arylsulfonates; D002351:Carrageenan; D015335:Molecular Probes; D000099166:Polyacrylamides; C005047:pyranine