Physico-chemical properties of polycarboxylate gel phase and their incidence on the retention/release of solutes | [Proprietes physicochimiques de la phase gel polycarboxylate et les effets sur la retention/liberation de solutions]
1999
Mestdagh, M.M. (Universite Catholique de Louvain, Louvain la Neuve (Belgique). Unite de Chimie des Interfaces) | Axelos, M.A.V.
Numerous applications of synthetic or biological polyelectrolytes are based upon the control of their interactions with multivalent ions. In the phase diagram of natural polycarboxylates obtained by addition of divalent cations in aqueous solutions, three major types of behavior were identified on the basis of the position and shape of the demixing line depending on the charge density and the cation/polyion affinity. A model was proposed for quantitative prediction of the demixing and sol-gel transition. The local configuration of the backbone promote intermolecular cross-links, leading to large gel phase. In the field of bioencapsulation, many applications are based on the diffusion properties of various solutes into or out of gelled networks. Polycarboxylate gel beads are of len used as a matrix to entrap molecules of biological significance. The elasticity of the beads increases with the cation/polyion affinity and this parameter is also responsible for their syneresis behavior. The cation's concentration, the ionic strength and the pH determine the kinetics of the gel formation as well as the volume and the stability of the beads. The pore size distributions vary and influence the diffusion of molecules. The partition coefficients are affected by the pH and/or the ionic strength of the medium
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