THE GELATION OF SODIUM ALGINATE WITH CALCIUM-IONS STUDIED BY MAGNETIC-RESONANCE-IMAGING (MRI)

The displacement of the sol/gel interface during the gelation of sodiu m alginate by calcium ions can be tracked in both one and two dimensio ns using magnetic resonance imaging. In the one-dimensional gelation e xperiments, the distance moved by the sol/gel interface was proportion al to (time(1/2)), which implies that the gelation process is diffusio n-limited. Using the gelation model previously proposed by Smidsrod an d co-workers, together with the initial reaction conditions and assumi ng that the diffusion coefficient of the alginate molecules is extreme ly small, it was found that the diffusion of calcium ions through the gel network is dependent on the initial concentration of the calcium, the ionic strength of the alginate solution, and the size of pores in the gel which is formed.