Now showing items 1-7 of 7

  • Comparison of cation effects on phase transitions of kappa and iota carrageenan 

    Authors:Tari, Ozlem; Pekcan, Önder
    Publisher and Date:(European Polymer Federation, 2010)
    Phase transitions of kappa and iota carrageenan in KCl NaCl and CaCl2 solutions were separately studied during heating and cooling processes by using fluorescence technique. Scattered light I-SC and fluorescence intensity I was monitored against temperature to determine the critical transition temperatures and exponents. Kappa and iota carrageenans with monovalent (KCl NaCl) salt system presented only coil to double helix (c-h) and double helix to coil (h-c) transitions upon cooling and heating ...

  • Critical Exponents of Kappa Carrageenan in the Coil-Helix and Helix-Coil Hysteresis Loops 

    Authors:Tari, Ozlem; Kara, Selim; Pekcan, Önder
    Publisher and Date:(Taylor & Francis Inc, 2009)
    The steady-state fluorescence technique was used to study coil-helix (sol-gel) and helix-coil (gel-sol) transitions of the kappa carrageenan-water system with various carrageenan contents. Fluorescence (I) and scattered light (I-sc) intensities were measured against temperature to determine critical phase transition temperatures and exponents. It was observed that the coil-helix transition temperatures T-ch were much lower than the helix-coil (T-hc) transition temperatures due to the hysteresis ...

  • Critical Exponents of Thermal Phase Transitions of kappa-Carrageenan in Various Salt Solutions 

    Authors:Tari, Ozlem; Pekcan, Önder
    Publisher and Date:(Wiley-VCH Verlag GmbH, 2009)
    The steady state fluorescence (SSF) technique was employed to study the phase transitions Of kappa-carrageenan in NaCl and KCl solutions. Pyranine was used as a fluorescence probe for monitoring these transitions. Scattered light I(sc) and fluorescence intensity 1 was monitored against temperature to determine transition temperatures and exponents. It was observed that transition temperatures are strongly correlated with the NaCl and KCl contents. The weight-average degree of polymerization DP(w) ...

  • Fluorescence study on drying of iota-carrageenan gels at different temperatures prepared with various CaCl2 content 

    Authors:Tari, Ozlem; Pekcan, Önder
    Publisher and Date:(Springer, 2011)
    The influence of temperature and salt content on drying was investigated by using steady-state fluorescence (SSF) technique. Supporting gravimetric and volumetric measurements were also carried out during drying of gels at various temperatures. iota-Carrageenan gels were prepared with various CaCl2 content. Pyranine was introduced as a fluorescence probe during gel preparation. Apparent fluorescence intensity I was measured during in situ drying process at each temperature and it was observed that ...

  • Modelling of Swelling by the Fluorescence Technique in Kappa Carrageenan Gels 

    Authors:Tari, Ozlem; Pekcan, Önder
    Publisher and Date:(Amer Inst Physics, 2011)
    Kappa (-kappa) carrageenan gels prepared with various carrageenan concentrations in pure water were completely dried and then swelled in water vapor. Steady state fluorescence measurements were performed using a spectrometer equipped with temperature controller. Pyranine was embedded in kappa-carrageenan gels as a fluorescence probe during gel preparation. The fluorescence intensity I increased exponentially as swelling time is increased for all gel samples. The increase in I was modelled using ...

  • Study of Thermal Phase Transitions in Iota Carrageenan Gels via Fluorescence Technique 

    Authors:Tari, Ozlem; Kara, Selim; Pekcan, Önder
    Publisher and Date:(Wiley-Blackwell, 2011)
    The effect of carrageenan concentration on thermal phase transitions of the iota carrageenan gels was investigated by using fluorescence technique. During heating and cooling processes scattered light I(sc) and fluorescence intensity I(p) were monitored against temperature to investigate phase transitions. Transition temperatures from the derivative of the transition paths were determined. Two regions were observed during the heating and cooling processes. At the first step of the heating dimers ...

  • Thermal Phase Transitions of IOTA Carrageenan in CaCl2 Solutions: A Fluorescence Study 

    Authors:Tari, Ozlem; Kara, Selim; Pekcan, Önder
    Publisher and Date:(Taylor & Francis Inc, 2011)
    The fluorescence technique was employed to study thermal phase transitions of iota (-) carrageenan (IC) in CaCl2 solution. IC gels underwent coil to double helix (c-h) and double helix to dimer (h-d) transitions upon cooling. Upon heating IC gels presented dimer to double helix (d-h) and double helix to coil (h-c) transitions showing hysteresis types of transition paths. Scattered light Isc and fluorescence intensity I were monitored against temperature to determine phase transitions. Transition ...