STUDY OF CRYOSTRUCTURIZATION OF POLYMER SYSTEMS .9. POLY(VINYL ALCOHOL) CRYOGELS FILLED WITH PARTICLES OF CROSS-LINKED DEXTRAN GEL

The influence of deformable disperse filler on rheological and thermal properties of poly(vinyl alcohol) cryogels (obtained by freezing-thawing of concentrated aqueous solutions of the polymer) was studied. Spherical particles of crosslinked dextran gel-the Sephadex beads of two types: G-25 and G-100 - were used as filler. It was found that an increase in the filler concentration from 0 to 20 wt % produced an increase in the composite cryogel strength; the greater reinforcement effect was observed with large-pore Sephadex beads into the cryogel matrix. An increase in the fraction of disperse phase also leads to an increase in fusion temperatures of these composites, such effect being determined mainly by the filler type. The filling of cryogels with G-100 beads improves the thermostability of composite samples to a higher extent as compared with the use of G-25 particles. Several possible reasons for the trends observed in rheological and thermal properties of Sephadex-filled PVA cryogels were revealed.