Study of properties of aqueous solutions of polyelectrolyte and non-ionic polymer mixtures

Study of cryostructurization of polymer systems VII. Structure formation under freezing of poly(vinyl alcohol) aqueous solutions

“…Earlier, in the works of other authors [1][2][3][4][5], it has been shown that freezing of concentrated aqueous solutions of poly(vinyl alcohol) (PVA), their standing in a frozen state and subsequent thawing result in mechanically firm gels (cryogels) which are stable in the definite temperature diapason. The formation of these cryogels proceeds due to the appearance of a threedimensional network stabilized by non-covalent interactions [1,[4][5][6][7][8].…”

A Brief History of Polymeric Cryogels

“…These findings initiated numerous fundamental studies due to the amazing combination of cryogel properties and their macroporous structure. The investigations of frozen PVA solutions by nuclear magnetic resonance (NMR) and electron spin resonance (ESR) allowed better understanding of the fine details of the gelation processes inside frost-bound Table 3 The examples of systems for the preparation of noncovalent (physical) cryogels Preparation of the gum-based cryogels, study of the influence of freezing rate and freeze/ thaw cycles number on the physicochemical properties of resulting cryogels [284][285][286][287] (continued) Apparently the first report on the empiric observation of the fact of PVA cryogel formation [230] 88.8/99.3 (2.5-15 wt%)…”

“…First, there were mainly empiric recordings on the formation of these cryogels [230,231] and the first patents were issued on the "virtual" applied possibilities of such materials [226][227][228][229]. Almost 10 years later, two approaches for increasing the strength of PVA cryogels were reported, namely, multiple freeze-thaw processing [299,[365][366][367][368][369][370] and the partial dehydration of frozen specimens in vacuo [9,300,301,371].…”

“…The majority of these studies are related to poly(vinyl alcohol) (PVA) cryogels, which have been known since the 1970s [226][227][228][229][230][231]. The formation mechanisms of PVA cryogels [1,29,[232][233][234][235][236][237] and their applications in various fields have been investigated extensively.…”

Cryostructuring of Polymeric Systems: 67 Properties and Microstructure of Poly(Vinyl Alcohol) Cryogels Formed in the Presence of Phenol or Bis-Phenols Introduced into the Aqueous Polymeric Solutions Prior to Their Freeze–Thaw Processing

“…The phenomenology of the freeze–thaw-induced sol-to-gel transformation of poly(vinyl alcohol) ( PVA ) aqueous solutions has been known since the 1970s [ 1 , 2 , 3 ]. The final “products” of such cryogenic processing (freezing—incubation in a frozen state—thawing) are gels that possess macroporosity and rubber-like elasticity [ 4 , 5 , 6 ].…”