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Yayın Temperature effect on drying and swelling of kappa carrageenan gels: A steady state fluorescence study(Wiley-V C H Verlag GMBH, 2008) Tarı İlgin, Özlem; Pekcan, Mehmet ÖnderA novel technique based on in situ steady state fluorescence (SSF) measurements is introduced for studying drying and swelling Of kappa(-) carrageenan (kappa carrageenan) gels at various temperatures. kappa(-) carrageenan gels were completely dried and then swelled in water vapor. Pyranine was embedded in kappa(-) carrageenan and used as a fluorescence probe. Scattered light intensities, I-SC and fluorescence intensities, I were monitored during the drying and swelling Of kappa(-) carrageenan gels. it was observed that the fluorescence intensity decreased linearly as drying time was increased. A simple model consisting of Case II diffusion was used to quantify the drying processes of the kappa(-) carrageenan gels. This moving boundary model provided packing constant, kappa(o). During swelling, fluorescence intensity increased exponentially as time is increased. The increase in I, was modeled using Li-Tanaka equation from which swelling time constants, tau(c) and cooperative diffusion coefficients, D-c were determined. It was observed that swelling time constants, tau(c) decreased and diffusion coefficients, D-c increased as the swelling temperature was increased. Activation energies for drying and swelling were also obtained and found to be 53.9 and 47.2 kJ mol(-1), respectively.Yayın Cation effect on gel-sol transition of kappa carrageenan(Springer, 2008-04) Pekcan, Mehmet Önder; Tarı İlgin, ÖzlemThe steady state fluorescence (SSF) technique was employed to study gel - sol transitions of kappa carrageenan in NaCl, KCl and CaCl2 solutions. Pyranine was used as a fluorescence probe for monitoring these transitions. Scattered light, I-sc and fluorescence intensity, I was monitored against temperature to determine the gel - sol (T-gs) transition temperatures and exponents. It was observed that T-gs values are strongly correlated to the NaCl, KCl and CaCl2 contents. The weight average degree of polymerization, DPw and gel fraction G, exponents (gamma and beta) were measured and found to be in accord with the classical Flory-Stockmayer Model.Yayın Swelling of iota-carrageenan gels prepared with various CaCl2 content: A fluorescence study(European Polymer Federation, 2008-01-05) Tarı İlgin, Özlem; Pekcan, Mehmet ÖnderIota carrageenan gels prepared with various CaCl2 content were completely dried and then swelled in water vapor. Steady-state fluorescence ( SSF) technique was used to monitor the swelling process of each iota carrageenan gels at various temperatures. Pyranine was used as a fluorescence probe. Apparent fluorescence intensity, I increased as swelling time increased for all gel samples. The increase in I was modelled using Li-Tanaka equation from which the swelling time constants, tau(1) and cooperative diffusion coefficients, D-c were determined. It was observed that D-c increased as the swelling temperature was increased. On the other hand at each temperature, it was seen that D-c decreased as CaCl2 content was increased. Activation energies for swelling were obtained and found to be 60.5, 61.0, 61.5 and 62.8 kJmol(-1) for the gels prepared with increasing amount of CaCl2 content.Yayın Swelling activation energy of kappa-carrageenan in its gel state: A fluorescence study(John Wiley & Sons Inc, 2007-12-15) Tarı İlgin, Özlem; Pekcan, Mehmet ÖnderA steady-state fluorescence technique was employed to study the swelling Of K-carrageenan gels at various temperatures. Pyranine was used as a fluorescence probe. The fluorescence intensity of pyranine was measured during the in situ swelling process of K-carrageenan gels. The fluorescence intensity increased exponentially as the swelling time increased. The increase in the fluorescence intensity was modeled with the Li-Tanaka equation, from which the swelling time constants and cooperative diffusion coefficients were determined. The swelling time constants decreased and the cooperative diffusion coefficients increased as the swelling temperature was increased. The swelling activation energies were measured to be 47.05 kJ/mol.Yayın Study of drying of kappa-carrageenan gel at various temperatures using a fluorescence technique(Taylor & Francis Inc, 2008-01) Tarı İlgin, Özlem; Pekcan, Mehmet ÖnderThe steady-state fluorescence technique was used to study drying of kappa-carrageenan gel at various temperatures. Pyranine was doped as a fluorescence probe, and scattered light, I-sc, and fluorescence intensities, I, were monitored during drying of these gels. It was observed that I decreased linearly as drying time is increased. The moving boundary model based on Case II diffusion was applied to produce the packing constants, k(0), at higher temperatures. Activation energy for drying was found to be 53.9 kJ mol(-1). Supporting gravimetric and volumetric measurements were also carried out during drying of gels and the corresponding activation energies were determined to be 46.4 and 58.9 kJ mol(-1), respectively.Yayın Slow release from carrageenan gels at various temperatures(Prous Science, SA, 2007-07) Tarı İlgin, Özlem; Pekcan, Mehmet Önder[No abstract available]Yayın Universality of sol-gel phase transition of kappa-carrageenan in various salts: a steady state fluorescence study(Taylor & Francis Ltd, 2007-08) Pekcan, Mehmet Önder; Tarı İlgin, ÖzlemThermal phase transitions of kappa-carrageenan in NaCl, KCl and CaCl2 solutions were studied using steady state fluorescence (SSF) technique. Pyranine was introduced as a fluorescence probe for studying sol-gel phase transitions. Scattered light, I-sc and fluorescence intensity, I was monitored against temperature to determine the sol-gel (T-sg) phase transition temperatures. It was observed that T-sg values are strongly correlated to NaCl, KCl and CaCl2 contents. The weight average degree of polymerization, DPw, and gel fraction G, exponents (gamma and beta) were measured and found to be in accord with the classical Flory-Stockmayer model, i.e., gamma and beta were found to be close to 1.0, independent of salt content.
