Cation effects on phase transition of kappa-iota-carrageenan hybrids: a photon transmission study (original) (raw)

Swelling activation energy of κ-carrageenan in its gel state: A fluorescence study

Journal of Applied Polymer Science, 2007

A steady-state fluorescence technique was employed to study the swelling of j-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 j-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.

Photon transmission study on swelling of κ-carrageenan gels prepared in various concentrations

International Journal of Biological Macromolecules, 2003

The photon transmission method was applied to study the scaling of thermal hysteresis at the nematicsmectic-A transition in a binary mixture of 4-ethoxy-4Ј-͑6-vinyloxyhexyloxyl͒ azobenzene monomer, smectogen, and 4-hexoxy-3Ј-methly-4Ј-͑6-acryloyloxyhexyloxy͒ azobenzene. The thermal hysteresis loops were obtained under linearly varying temperature. It has been found that the area A of the hysteresis loops scales with the temperature scanning rate R as AϭA 0 ϩbR n with the exponent n equal to 0.692, which is consistent with the (⌽ 2 ) 3 field theoretical model value within the experimental resolution.

Cation effect on gel – sol transition of kappa carrageenan

Polymer Bulletin, 2008

A novel technique based on in situ steady state fluorescence (SSF) measurements is introduced for studying drying and swelling of kcarrageenan (kappa carrageenan) gels at various temperatures. kcarrageenan gels were completely dried and then swelled in water vapor. Pyranine was embedded in kcarrageenan and used as a fluorescence probe. Scattered light intensities, I sc and fluorescence intensities, I were monitored during the drying and swelling of kcarrageenan 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 kcarrageenan gels. This moving boundary model provided packing constant, k 0 . 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, t c and cooperative diffusion coefficients, D c were determined. It was observed that swelling time constants, t 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 À1 , respectively.

Cation effects on sol–gel and gel–sol phase transitions of κ-carrageenan–water system

International Journal of Biological Macromolecules, 2003

Carrageenan gels prepared with various carrageenan concentrations in pure water were completely dried and then swelled in pure water. Photon transmission measurements were performed using a UV-Vis (UVV) spectrometer during the swelling of -carrageenan gels. Transmitted photon intensity, I tr , increased exponentially as swelling time is increased for all gel samples. The behaviour of I tr was interpreted by Monte-Carlo Simulation. The increase in I tr was quantified by employing Li-Tanaka equation, from which time constants τ 1 and collective diffusion coefficients, D o were determined for the gels in various carrageenan concentrations. Gravimetric and volumetric measurements were also carried out during swelling of gels. It is observed that gel with high carrageenan content possess more double helices and more lattice dislocations and swell slower than gels with low carrageenan content which may contain less double helices and less lattice imperfections. Increase in I tr was interpreted by the homogeneous distribution of double helices in the carrageenan gel system.

Molecular recognition during sol–gel and gel–sol transition of kappa–iota carrageenan mixtures

Phase Transitions, 2005

Sol-gel and gel-sol phase transitions of kappa-iota (-) carrageenan mixtures in two types of salts were studied using photon transmission technique. Here, KCl and CaCl 2 were chosen as the proper salts for the carrageenan mixtures. Coil-to-double helix (c-h) and double helix-to-dimer (h-d) phase transitions of carrageenan mixtures in monovalent and bivalent cation solutions were studied upon heating and cooling by using photon transmission technique. Photon transmission intensity, I tr was monitored against temperature to determine the (c-h) and (h-d) transition temperatures (T ch and T nd ). Two distinct transition regions were observed in both heating and cooling of the carrageenan-bivalent CaCl 2 salt system. At the first step of heating process dimers decompose into double helices by making (d-h) transition. At the high temperature region (h-c) transition takes place. Carrageenan-monovalent KCl salt system presented only (c-h) and (h-c) transitions upon cooling and heating processes. Transition temperatures at the heating and cooling processes were obtained. A hysteresis was observed between (h-c)-(c-h) and (d-h)-(h-d) transitions for the monovalent and bivalent cations respectively.

Cation effects on swelling of ?-carrageenan: A photon transmission study

Biopolymers, 2003

Photon transmission techniques were used to study sol-gel and gel-sol transitions in -carrageenan-water systems with various carrageenan contents. The photon transmission intensity, I tr was monitored against temperature to determine critical phase transition temperatures and transition rates. It was observed that the sol-gel transition temperatures, T sg , were found much lower than the gel-sol, T gs , transition temperatures based on the hysteresis of the phase transition loops. Sol-gel and gel-sol activation energies were determined and it was found that a carrageenan-water system required less energy for the gel-sol transition than for the sol-gel transition.

Small Molecule Diffusion into Swelling Iota-Carrageenan Gels: A Fluorescence Study

Journal of Biomolecular Structure and Dynamics, 2007

Small molecule sorption and desorption in and out of Iota-Carrageenan was studied by using steady-state fluorescence (SSF) technique. Pyranine dissolved in water used as fluorescence probe. Fluorescence emission intensity, I p from pyranine was monitored for studying sorption and desorption processes at various temperatures. The Fickian model was applied to produce sorption, D s , early desorption, D ed , and desorption, D d , coefficients. Corresponding activation energies were obtained and found to be 20.5 kJ mol 21 , 7.0 kJ mol 21 and 34.9 kJ mol 21 , respectively. The observed D ed value is an order of magnitude smaller than the D s and D d coefficients. On the other hand, sorption processes were shown to be twice as fast as desorption processes.

Swelling of iota-carrageenan gels prepared with various CaCl2 content: A fluorescence study

e-Polymers, 2008

Iota carrageenan gels prepared with various CaCl 2 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, τ 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 CaCl 2 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 CaCl content. 2

Phase transitions of κ-carrageenan gels in various types of salts

Journal of Applied Polymer Science, 2006

Sol-gel and gel-sol phase transitions of k-carrageenan in various types of salts were studied using photon transmission technique. Here, LiCl, NaCl, KCl, MgCl 2 , CaCl 2 , and SrCl 2 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 (DE sg and DE 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.