Structure formation in biopolymer gels induced by diffusion of gelling factors

When biopolymer solutions come in contact with a coagulation bath containing a gelling factor such as ions, chemical crosslinkers, and pH conditioners, diffusion of the gelling factor through the contact interface into the polymer solutions induces gelation, which proceeds gradually in a direction along the diffusion of the gelling factor. In this directional gelation process, characteristic structures are frequently formed in the biopolymer gels. This review presents general features of the structure formation by the diffusion of the gelling factors and some specific examples for typical biopolymers.