Isotropic-nematic phase equilibrium and phase separation of kappa-carrageenan in aqueous salt solution: Experimental and theoretical approaches

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Isotropic-nematic phase equilibrium and phase separation of kappa-carrageenan in aqueous salt solution: Experimental and theoretical approaches. / Chronakis, Ioannis S; Ramzi, M.

I: Biomacromolecules, Vol. 3, Nr. 4, 2002, s. 793-804.

Forskningsoutput: TidskriftsbidragArtikel i vetenskaplig tidskrift

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T1 - Isotropic-nematic phase equilibrium and phase separation of kappa-carrageenan in aqueous salt solution: Experimental and theoretical approaches

AU - Chronakis, Ioannis S

AU - Ramzi, M

PY - 2002

Y1 - 2002

N2 - The behavior of chiral-nematic and isotropic phases of helical kappa-carrageenan in aqueous solution of sodium iodide was compared with that of the anisotropic biphasic phase that contains both these phases. On the basis of birefringence, rheology, chemical analysis, average molecular weight, and polydispersity index measurements, we derived a number of characteristic differences as well as similarities between these phases, over a range of polysaccharide concentrations obtained by the dilution of each phase. For example, we assessed the critical concentration of an isotropic-anisotropic transition (C-i), the temperature of the anisotropic-isotropic phase shift during thermal heating-cooling cycles, and the viscosity changes due to the phase shift and due to the diminishing of the helical conformation. We also demonstrated how the different phases and their dilutions behave under the effect of shear and frequency of oscillation and how the viscoelastic properties vary in each phase and discussed the isotropic and anisotropic liquid crystal controlling behavior mechanisms. From a theoretical point of view, we propose to combine the wormlike chain model for semiflexible polyelectrolytes interacting via both hard-core and electrostatic repulsion to assess the concentration of isotropic-nematic transition, to assess the coexistence concentration range, and to determine the effects of charge by applying the effective diameter and a twisting effect.

AB - The behavior of chiral-nematic and isotropic phases of helical kappa-carrageenan in aqueous solution of sodium iodide was compared with that of the anisotropic biphasic phase that contains both these phases. On the basis of birefringence, rheology, chemical analysis, average molecular weight, and polydispersity index measurements, we derived a number of characteristic differences as well as similarities between these phases, over a range of polysaccharide concentrations obtained by the dilution of each phase. For example, we assessed the critical concentration of an isotropic-anisotropic transition (C-i), the temperature of the anisotropic-isotropic phase shift during thermal heating-cooling cycles, and the viscosity changes due to the phase shift and due to the diminishing of the helical conformation. We also demonstrated how the different phases and their dilutions behave under the effect of shear and frequency of oscillation and how the viscoelastic properties vary in each phase and discussed the isotropic and anisotropic liquid crystal controlling behavior mechanisms. From a theoretical point of view, we propose to combine the wormlike chain model for semiflexible polyelectrolytes interacting via both hard-core and electrostatic repulsion to assess the concentration of isotropic-nematic transition, to assess the coexistence concentration range, and to determine the effects of charge by applying the effective diameter and a twisting effect.

U2 - 10.1021/bm020015k

DO - 10.1021/bm020015k

M3 - Article

VL - 3

SP - 793

EP - 804

JO - Biomacromolecules

T2 - Biomacromolecules

JF - Biomacromolecules

SN - 1526-4602

IS - 4

ER -