A hierarchical model of crystallization in polymeric gels and porous solids

A kinetic model of the crystallization of substances in the volume of an agglomerate of many microparticles or in a polymeric gel in solution with a given composition and temperature was formulated. The model takes into account the diffusion of the crystallizing substance from outside into the space between microparticles in an agglomerate or between polymeric globules in a gel and then from this space into the volume of microparticles (globules) with the simultaneous nucleation and growth of microcrystals of the crystallizing substance. The possibility of simultaneous diffusion of several crystallizing substances, which chemically react with each other to produce product microcrystals, heating of the gel (solid) by the heat of crystallization, pushing the solution out from the space between microparticles, and changes in the volume of the gel (solid) as a result of crystallization is considered. The model was used to develop a classification of crystallization types in gels and porous solids and interpret several phenomena described in the literature. A hypothesis was advanced concerning some unknown phenomena related to crystallization.