Study of Cryostructuration of Polymer Systems. XX. Foamed Poly(vinyl acohol) Cryogels

摘要

Foamed poly(vinyl alcohol) (PVA) cryogels, which are formed as a result of freeze-thaw treatment of whipped PVA water solutions (polymer with MW of 69,000 Da and DD approx 99 mol % was used), wer obtained and their propeties were studied. The rheological characteristics and macrostructure of these gel materials were controlled by the same factors as for the ordinary nonfoamed PVA cryogels (initial polymer concentration and freezing-thawing regimes) and also by the conditions of generation of fluid PVA foams. The study of the kinetics of the freeze-thaw-induced gel formation of these foams revealed that the temperature dependence of the efficiency of cryotropic gelation showed a maximum at about -1.5 deg C. The presence of low molecular weight admixtures in the initial polymer solution appears to be a rather important factor because the admixtures were capable of decreasing the stability of fluid PVA foams and weakening both foamed and nonfoamed cryogel samples.