DENSITY DISTRIBUTION OF CALCIUM-INDUCED ALGINATE GELS - A NUMERICAL STUDY

Charged polysaccharides often form hydrogels in the presence of cations. In many applications the polymer network density distribution and associated physical properties are of major practical importance. Depending on the detailed conditions, the resulting gel density may vary from fully homogeneous to strongly inhomogeneous. We have established a simple set of coupled chemical reaction-diffusion equations to model the gelling process of calcium-induced alginate gels. The necessary algorithms for numerical solution of the resulting simultaneous parabolic differential equations have been developed both for one-dimensional models and three-dimensional models with cylindrical or spherical symmetry. The algorithms make use of the Crank-Nicolson implicit finite difference method. The results of the numerical analyses of the gel formation can be divided into several different regimes depending on the physical and chemical parameters of the alginates and the cations. The numerical results are in good agreements with reported experimental results. (C) 1995 John Wiley & Sons, Inc.