STUDY OF CRYOSTRUCTURATION OF POLYMER SYSTEMS .11. THE FORMATION OF PVA CRYOGELS BY FREEZING-THAWING THE POLYMER AQUEOUS-SOLUTIONS CONTAINING ADDITIVES OF SOME POLYOLS

The influence of the presence of some polyols in initial poly(vinyl al cohol) aqueous solutions on theological and thermal properties of the cryogels, which were produced by the freezing-thawing method, was inve stigated. The polyol additives (cosolvents) were as follows: glycerol, propylene glycol, mono-, di-, and triethylene glycols, and oligoethyl ene glycols (PEG-400 and PEG-1000). It was shown that the introduction of glycerol, propylene, or ethylene glycols into the polymer solution resulted in a decrease of cryogel's shear modulus and fusion temperat ure, whereas the use of triethylene and higher ethylene glycol oligome rs as cosolvents gave rise to an increase in the gel's strength and th ermostability, and diethylene glycol exhibited a transitional influenc e. The possible mechanism of the action of reinforcing cosolvents is d iscussed. (C) 1995 John Wiley & Sons, Inc.