Basic Principles of Cryotropic Gelation
Vladimir I. Lozinsky and Oguz Okay
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
1.1 “Gels” in General, and “Cryogels” in Particular . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
1.2 “Cryotropic Gelation” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
1.3 “Positive” and “Negative” Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
1.4 “Gel-Fraction” and “Gel-Fraction Yield” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
2 Main Stages of the Cryotropic Gelation Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
2.1 Preparation of the Feed System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
2.2 Freezing of the Feed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
2.3 Incubation of the Gelation System in a Frozen State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
2.4 Thawing of the Frozen System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
3 Specific Effects of Gel Formation in Moderately Frozen Systems . . . . . . . . . . . . . . . . . . . . . . . . . 66
3.1 Apparent Decrease in the Critical Concentration of Gelation . . . . . . . . . . . . . . . . . . . . . . . . 66
3.2 Acceleration of Gel Formation Over a Certain Range of Negative Temperatures . . 73
3.3 Bell-Shaped Temperature Dependence of Cryotropic Gelation Efficiency . . . . . . . . . . 78
3.4 Generation of Specific Porosity Peculiar to Cryogels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
Abstract Polymeric cryogels are the gel systems formed in moderately frozen
solutions or colloidal dispersions of precursors potentially capable of gelling.
Polymeric cryogels are of growing practical interest in various applied areas. The
fabrication of any cryogel includes the following necessary stages: preparation of
the feed system, its freezing, incubation of the gelation system in a frozen state, and
V.I. Lozinsky (*)
Laboratory for Cryochemistry of (Bio)Polymers, A.N. Nesmeyanov Institute of
Organoelement Compounds, Russian Academy of Sciences, Vavilov Street 28, 119991
Moscow, Russian Federation
e-mail: loz@ineos.ac.ru
O. Okay
Department of Chemistry, Istanbul Technical University, Maslak, 34469 Istanbul, Turkey
e-mail: okayo@itu.edu.tr
O. Okay (ed.), Polymeric Cryogels, Advances in Polymer Science 263,
DOI 10.1007/978-3-319-05846-7_2, © Springer International Publishing Switzerland 2014
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