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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 Critical behavior of thermal phase transitions of iota-carrageenan in CaCl2 solution(Elsevier B.V., 2006-07-15) Özbek, Haluk; Pekcan, Mehmet ÖnderIn situ photon transmission method was applied to study thermal phase transitions of ?-carrageenan in CaCl2 solution. Coil-to-helix (c-h) and helix-to-dimer (h-d) transitions were detected upon cooling. An extra dimer-to-dimer (d-d) transition was observed as well during cooling at low-temperature region. Upon heating only dimer-to-helix (d-h) and helix-to-coil (h-c) transitions were detected. Photon transmission intensity, Itr was monitored against temperature to determine several phase transitions and transition temperatures. It was observed that the c-h transition in ?-carrageenan-CaCl2 system performs a crossover between 3D percolation to classical theory. Upon heating, the specific heat exponent over the d-h transition was extracted from the transmitted intensity data and was found to be 0.045.Yayın Phase transitions of kappa-carrageenan gels in various types of salts(John Wiley & Sons Inc, 2006-11-05) Kara, Selim; Arda, Ertan; Kavzak, Burhan; Pekcan, Mehmet ÖnderSol-gel and gel-sol phase transitions of K-carrageenan in various types of salts were studied using photon transmission technique. Here, LiCl, NaCl, KCl, MgCl2, CaCl2, and SrCl2 were chosen as the proper salts for the K-carrageenan-water system. Photon transmission intensity, I-tr was monitored against temperature to determine the sol-gel and gel-sol temperatures (T-sg and T-gs) and activation energies (Delta E-sg and Delta E-gs). It was observed that T-gs temperatures were notably higher than T-sg due to the hysteresis on the phase transition loops. It was observed that stronger carrageenan gels are formed in the presence of KCl compared to the others.
