Study of cryostructuration of polymer systems. XVII. Poly(vinyl alcohol) cryogels: Dynamics of the cryotropic gel formation

Lozinsky, V. I.; Damshkaln, Lilija G.

doi:10.1002/1097-4628(20000829)77:9<2017::aid-app18>3.0.co;2-6

Cited by 56 publications

(48 citation statements)

References 19 publications

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“…For foamed cryogels free of surfactants, the same regularity was observed also for the fusion temperature, i.e., the most high fusible were the samples incubated at -2.5°C. This coincides completely with the tendency that is known for common PVA cryogels, for which the temperature range from -2 to -3°C is the region of the most efficient gelation [23,24].…”

Section: The Effect Of the Conditions Of Cryotropic Gelation On The Psupporting

confidence: 87%

“…1b, 2b, 3b, and 4b (freezing at -30°C, incubation at -20°C, and thawing at a rate of 0.3°C/min). The thawing of samples at a tenfold slower rate corresponds to tenfold increase in the time of system gelation at negative temperatures that are optimal for cryotropic gelation [1,23,24]. With account of very high viscosity of unfrozen part of water-PVA system [28] (so-called unfrozen liquid mesophase [29] where the cryogel is formed [1,6]), such an increase in the duration of a process ensures not only more ordered arrangement of porogen particles (ice polycrystals) but also more complete incorporation of PVA macromolecules into the 3D network of physical gel [1,23,30].…”

Section: Peculiarities Of the Morphology Of Gas-filled Pva Cryogels Fmentioning

confidence: 99%

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Study of Cryostructuring of Polymer Systems: 25. The Influence of Surfactants on the Properties and Structure of Gas-Filled (Foamed) Poly(vinyl alcohol) Cryogels

et al. 2005

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Foamed poly(vinyl alcohol) (PVA) cryogels are studied. Such heterogeneous gel composites are formed as a result of the cryogenic treatment (freezing-storage in a frozen state-thawing) of water-PVA liquid foams in the absence and presence of surfactants. It is shown that the addition of ionic and nonionic surfactants to an aqueous PVA solution and its subsequent foaming result in the formation of liquid foam whose stability is lower than that of the foam prepared from an aqueous PVA solution in the absence of surfactant, i.e., surfactants cause a destabilizing effect on the foams containing PVA. Gas-filled PVA cryogels formed as a result of freezing-thawing of such foams contain large (up to ~ 180 µ m) pores (air bubbles incorporated into the matrix of heterogeneous gel). Mechanical and thermal properties of cryogels depend on the nature and concentration of surfactants, as well as on the regime of cryogenic treatment. The rigidity of foamed PVA cryogels prepared in the presence of sodium dodecyl sulfate and cetyltrimethylammonium bromide ionic surfactants is lower and that in the presence of nonionic decaoxyethylene cetyl ether is higher than for equiconcentrated (by the polymer) foamed PVA cryogel containing no surfactant. Microscopic studies and the analysis of obtained images of cryogel structure demonstrate that the effect of surfactant on the morphology of freezing foam can be different, depending on the type of surfactant added to the initial system. This leads to foam-destabilizing effects such as the collapse, deformation, and coalescence of air bubbles; the failure of gel phase structure near the bubble surface; etc. However, the complete disintegration of the foamed structure is prevented by a very high viscosity of the unfrozen liquid microphase of a macroscopically solid sample and by the cryotropic PVA gelation that fixes the structure of partially destroyed foam.

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Section: The Effect Of the Conditions Of Cryotropic Gelation On The Psupporting

confidence: 87%

Section: Peculiarities Of the Morphology Of Gas-filled Pva Cryogels Fmentioning

confidence: 99%

Study of Cryostructuring of Polymer Systems: 25. The Influence of Surfactants on the Properties and Structure of Gas-Filled (Foamed) Poly(vinyl alcohol) Cryogels

et al. 2005

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“…Materials Natural MOM KSF [K 0.2 Ca 0.3 (Fe,Al,Mg) 8 (Si 4 O 10 ) 4 (OH) 8 .12H 2 O] with a cationic exchange capacity of about 60 mequiv. per 100 g and a surface area of about 15 m 2 Á g À1 was purchased from Acros.…”

Section: Experimental Partmentioning

confidence: 99%

“…[6] This interesting characteristic of PVA solutions has been used to produce PVA hydrogels without chemical crosslinkers to design non-toxic and biocompatible biomedical devices. [7][8][9] Montmorillonite (MOM) and bentonite are the main…”

Section: Introductionmentioning

confidence: 99%

Poly(vinyl alcohol)/Clay‐Based Nanocomposite Hydrogels: Swelling Behavior and Characterization

Paranhos

Soares

Oliveira

et al. 2007

Macro Materials & Eng

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Polymer/clay composite hydrogels were prepared based on PVA hydrogels containing 3–10 wt.‐% MOM. Their microstructure and morphology were studied by FT‐IR, WAXS and SEM, whereas the interactions between MOM and PVA were evaluated by thermal analyses. The swelling ratios for the PVA/MOM hydrogels decrease with increasing MOM content. WAXS results indicate that MOM was intercalates, and DSC results show a strong interaction between PVA and MOM. This interaction results in a stable network, which is confirmed by the elastic modulus and the thermal decomposition behavior of the hydrogels. Therefore, MOM acts as a co‐crosslinker, improving the stability of the network.magnified image

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“…The polymer gel phase is formed during one of the stages of the cryogenic treatment: during freezing of the initial system, during storage of the samples in the frozen state or during thawing of the frozen specimens. (1, [3][4][5][6] Recently, the structuring of different polymers by applying a cryogenic treatment has attracted a lot of attention, as indicated by the following examples. For a thiol-containing poly(acryl amide) derivative, the conditions were optimized in order to obtain an insoluble gel after freezing-thawing.…”

Section: Introductionmentioning

confidence: 99%

Effect of Cryogenic Treatment on the Rheological Properties of Gelatin Hydrogels

Vlierberghe

Dubruel

Schacht

2010

Journal of Bioactive and Compatible Polymers

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Above the critical gelation concentration, gelatin has the ability to form a gel when cooled below the sol-gel temperature. In the present work, freeze-thaw cycles were implemented on gelatin solutions possessing varying concentrations. The rheological properties of the cryogels developed were compared with hydrogels formed at room temperature. The results indicated that the rheological properties of cryogels were superior to those of the corresponding hydrogels formed at room temperature. In addition, the critical gelation concentration decreased after (repeated) cryo-treatment(s). The effect of applying various (cryo)parameters, including the number of freeze-thaw cycles, the cooling rate, the thawing rate and the gelatin concentration, on the final material properties was examined. The rheological properties of the cryogels improved with an increasing number of cryo-cycles and a decreasing cooling and thawing rate. In a second part of the work, methacrylamide-modified gelatin was treated cryogenically, followed by in situ UV-irradiation to enable radical crosslinking. It was shown that the crosslinking efficiency improved upon freeze-thawing. The latter was however limited by the gelatin concentration, which affects the chain mobility required to induce phase separation. The present work demonstrates that cryogelation offers possibilities to finetune the mechanical properties of hydrogels. The observed findings are of relevance for the field of tissue engineering, since this concept was previously applied for the development of porous gelatin hydrogels as biomaterials. In addition, a cryogenic treatment can be applied to a wide range of synthetic and natural polymers.-3 -

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Study of cryostructuration of polymer systems. XVII. Poly(vinyl alcohol) cryogels: Dynamics of the cryotropic gel formation

Cited by 56 publications

References 19 publications

Study of Cryostructuring of Polymer Systems: 25. The Influence of Surfactants on the Properties and Structure of Gas-Filled (Foamed) Poly(vinyl alcohol) Cryogels

Study of Cryostructuring of Polymer Systems: 25. The Influence of Surfactants on the Properties and Structure of Gas-Filled (Foamed) Poly(vinyl alcohol) Cryogels

Poly(vinyl alcohol)/Clay‐Based Nanocomposite Hydrogels: Swelling Behavior and Characterization

Effect of Cryogenic Treatment on the Rheological Properties of Gelatin Hydrogels

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