ИСТИНА

Polymeric cryogels and cryostructurates are the supramolecular matrices, whose formation occurs in the non-deeply frozen systems. When the buildup of the 3D polymeric network and its simultaneous cross-linking via chemical or physical bonds take place exactly in frozen sample, the final, i.e. after defrosting, matrices are the cryogels. If the feed solution of polymeric precursors is initially frozen, and the formed solvent crystals are further removed via sublimation or cryoextraction techniques, it results in obtaining a macroporous cryostructurate, which can be then fixed chemically using suitable cross-linking methods. Cryotropic gelation processes possess a set of specific features, when the main observed effects are as follows: (i) an apparent decrease in the critical concentration of gelation upon the preparation of cryogels as compared with gelling of the same precursors in the non-frozen liquid medium; (ii) an increase in the gelation rates over certain range of cryogenic temperatures compared with the rates of traditional gelation at temperatures above the freezing point (the temperature dependences of the parameters capable of reflecting the efficiency of gelation are, as a rule, of bell-shaped character); (iii) all cryogels are the macroporous gel matrices, since the crystals of frozen solvent perform as porogens, and the gel-formation itself occurs in between their particles in the space of so-called unfrozen liquid microphase, where solutes are concentrated. A fortunate combination of good physicochemical properties of diverse polymeric cryogels and cryostructurates with their specific porous morphology makes these materials attractive in various applied areas, especially as gel matrices of biomedical and biotechnological interests.