Browsing by Author "Tari, Ozlem"

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Citation Count: 6
Study of Thermal Phase Transitions in Iota Carrageenan Gels via Fluorescence Technique
(Wiley-Blackwell, 2011) Tari, Ozlem; Kara, Selim; Pekcan, Önder
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 were converted into double helix by undergoing dimer to double helix (d-h) transition. At the higher temperature region double helix to coil (h-c) transition took place. During the cooling process these transitions are arranged in the order of coil to double helix (c-h) and double helix to dimer (h-d). A hysteresis was observed between (h-d) and (d-h) transitions. The critical gel fraction exponents beta were found to be independent of the system by indicating that they all fall into the same universality class. (C) 2011 Wiley Periodicals Inc. J Appl Polym Sci 121: 2652-2661 2011
Citation Count: 1
Thermal Phase Transitions of IOTA Carrageenan in CaCl2 Solutions: A Fluorescence Study
(Taylor & Francis Inc, 2011) Tari, Ozlem; Kara, Selim; Pekcan, Önder
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 temperatures were determined from the derivative of the transition paths. The critical gel fraction exponent was measured and found to be in accord with the classic Flory-Stockmayer model.