Cryogels on the basis of natural and synthetic polymers: preparation, properties and application

This review deals with cryotropic gelation in polymeric systems, which takes place on moderate freezing, storing in a frozen state and subsequent thawing of solutions or colloidal dispersions containing monomeric or polymeric precursors. The polymer materials formed under these conditions are termed as cryogels. They are macroporous heterophase gels in which polycrystals of the frozen solvent act as porogens during gel formation. The current knowledge about the structure of moderately frozen solutions of low- and high-molecular-mass compounds is considered, the general regularities of the cryotropic gelation processes and their similarity to and differences from gelation at positive temperatures are discussed, the fields of application of cryotropic gelation techniques are described, and examples of using polymeric cryogel-based materials for solving applied problems are given. The bibliography includes 433 references.