Poly(Vinyl Alcohol) Cryogels Formed from Polymer Solutions in Dimethyl Sulfoxide with Tetramethoxysilane Additives

Organic–inorganic hybrid cryogels of poly(vinyl alcohol) (PVA) containing silica inclusions (SiO₂) were obtained and studied. Such inclusions were formed in the course of hydrolytic polycondensation (sol-gel process) of tetramethoxysilane (TMOS) introduced into concentrated polymer solutions in dimethyl sulfoxide (DMSO). PVA concentration in these solutions was 60, 80 or 100 g/L; while the concentration of TMOS was varied in a range of 0.15–0.61 mol/L. The polymer solutions were subjected to the cryogenic treatment at temperatures by 40 °С lower than DMSO crystallization temperature (+18.4°C). The frozen samples were thawed out at a heating rate of 0.03°/min. It is shown that moderate freezing at −21.6 °C, then frozen storage and subsequent thawing of the initial reaction mixture PVA/DMSO/TMOS/acid catalyst resulted in the formation of strong macroporous PVA/SiO₂ cryogels. Such cryogel materials are hybrid systems, because the gel-forming polymer and the silica containing moieties belong to the content of the gel phase. The basis of this intermolecular interaction is hydrogen bonding between OH groups of the adjacent chains. This leads to the formation of modified microcrystallinity zones that perform as the nodes of the three-dimensional network of cryogels. The effects of significant increase in their rigidity and heat-resistance with increasing PVA and TMOS concentration in the initial feed were also observed. It was shown that the success of the synthesis of transparent elastic and heat-resistant PVA/SiO₂ cryogels depends on the choice of the optimal ratio between the precursors and the combined effect of the liquid (methanol and water) and silicon-containing components on the formation of multiple hydrogen bonds and microcrystallites.

1. Lozinsky V.I. Cryogels on the basis of natural and synthetic polymers: preparation, properties and applications. Russ. Chem. Rev. 2002; 71(6):489-511.

2. Alves M.-H., Jensen B.E.B., Smith A.A.A., Zelikin A.N. Poly(Vinyl Alcohol) physical hydrogels: new vista on a long serving biomaterial. Macromol. Biosci. 2011;11(10): 1293-1313. (DOI:10.1002/mabi.201100145).

3. Lozinsky V.I. Cryotropic gelation of poly(vinyl alcohol) Russ. Chem. Rev. 1998; 67(7):573-586.

4. Willcox P.J., Howie D.W., Schmidt-Rohr K., Hoagland D.A., Gido S.P., Pudjijanto S., Kleiner L.W., Venkatraman S. Microstructure of Poly(vinyl alcohol) hydrogels produced by freeze/thaw cycling. J. Polym. Sci. Part B: Polymer Physics. 1999; 37(24): 3438-3454.

5. Kokabi M., Sirousazar M., Hassan Z.M. PVA– clay nanocomposite hydrogels for wound dressing // Eur. Polym. J. 2007; 43(3):773-781. (DOI:10.1016/j.eurpolymj.2006.11.030)

6. Pan Y., Xiong D., Chen X. Mechanical properties of nanohydroxyapatite reinforced poly(vinyl alcohol) gel composites as biomaterial. J. Mater. Sci. 2007; 42(13):5129-5134. (DOI:10.1007/s10853-006-1264-4).

7. Bakeeva I.V., Ozerina L.A., Ozerin A.N., Zubov V.P. Structure and Characteristics of jrganic-inorganic hybrid hydrogels based on poly(N-vinylcaprolactam)-SiO2. Polymer Sci. Series A. 2010; 52(5):496-505. (DOI:10.1134/S0965545X10050044)

8. Cheng H.K.F., Sahoo N.G., Tan Y.P., Pan Y., Bao H., Li L., Chan S.H., Zhao J. Poly(vinyl alcohol) nanocomposites filled with poly(vinyl alcohol)-grafted graphene oxide. ACS Appl. Mater. & Interfaces. 2012; 4(5): 2387-2394. (DOI:10.1021/am300550n)

9. Bakeeva I.V., Egorova E.A., Perov N.S., Dementsova I.V., Chernikova E.V., Zubov V.P. Magnetosensitive organicinorganic hybrid hydrogels. Polymer Sci. Series B. 2014; 56(3):384-392. (DOI:10.1134/S1560090414030038)

10. Sanchez C., Rozes L., Ribot F., Laberty-Robert C., Grosso D., Sassoye C., Boissiere C., Nicole L. ‘‘Chimie douce’’: A land of opportunities for the designed construction of functional inorganic and hybrid organic-inorganic nanomaterials. Comptes Rendus Chimie. 2010; 13(1-2):3-39. (DOI:10.1016/j.crci.2009.06.001)

11. Lozinsky V.I., Bakeeva I.V., Presnyak E.P., Damshkaln L.G., Zubov V.P. Cryostructuring of polymer systems. XXVI. Heterophase organic-inorganic cryogels prepared via freezingthawing of aqueous solutions of poly(vinyl alcohol) with added tetramethoxysilane. J. Appl. Polym. Sci. 2007; 105(5):2689-2702. (DOI:10.1002/app.26360)

12. Hench L.L., West J.K. The sol-gel process. Chem. Rev. 1990; 90(1):33-72. (DOI:10.1021/cr00099a003)

13. Sol-gel science. The physics and chemistry of sol–gel processing, Ed. by Brinker C.J. and Scherer G.W., Academic Press Inc.: Boston 1990. xiv. 908 p. (https://doi.org/10.1002/adma.19910031025)

14. Rother D., Sen T., East D., Bruce I.J. Silicon, silica and its surface patterning/activation with alkoxy- and aminosilanes for nanomedical applications. Nanomedicine. 2011; 6(2):281-300. (DOI:10.2217/nnm.10.159)

15. Karimi A., Daud W.M.A.W. Nanocomposite cryogels based on poly(vinyl alcohol)/ unmodified Na+-montmorillonite suitable for wound dressing application: optimizing nanoclay content. J. Mineral. Metals & Mater. Soc. 2017; 69(7):1213-1220. (DOI:10.1007/s11837-016-2194-5)

16. Chaturvedi A., Bajpai A.K., Bajpai J., Singh S.K. Evaluation of poly(vinyl alcohol) based cryogel–zinc oxide nanocomposites for possible applications as wound dressing materials. Mater. Sci. & Eng. Part C. 2016; 65: 408-418. (DOI:10.1016/j.msec.2016.04.054)

17. Badranova G.U., Gotovtsev P.M., Zubavichus Y.V., Staroselskiy I.A., Vasiliev A.L., Trunkin I.N., Fedorov M.V. Biopolymer-based hydrogels for encapsulation of photocatalytic TiO2 nanoparticles prepared by the freezing/ thawing method. J. Mol. Liquids. 2016; 223:16-20. (DOI:10.1016/j.molliq.2016.07.135)

18. Abudabbus M.M., Jevremovic I., Jankovic A., Peric-Grujic A., Matic I., Vukasinovic-Sekulic M., Hui D., Rhee K.Y., Miskovic-Stankovic V. Biological activity of electrochemically synthesized silver doped polyvinyl alcohol/graphene composite hydrogel discs for biomedical applications. Composites. Part B. 2016; 104:26-34. (DOI:10.1016/j.compositesb.2016.08.024)

19. Chen K., Liu J., Yang X., Zhang D. Preparation, optimization and property of PVA-HA/PAA composite hydrogel. Mater. Sci. & Eng. Part C. 2017; 78: 520-529. (DOI:10.1016/j.msec.2017.04.117)

20. Su C., Su Y., Li Z., Haq M.A., Zhou Y., Wang D. In situ synthesis of bilayered gradient poly (vinyl alcohol)/ hydroxyapatite composite hydrogel by directional freezing-thawing and electrophoresis method. Mater. Sci. & Eng. Part C. 2017; 77:76-83. (DOI:10.1016/j.msec.2017.03.136)

21. Timofejeva A., D'Este M., Loca D. Calcium phosphate/polyvinyl alcohol composite hydrogels: A review on the freeze-thawing synthesis approach and applications in regenerative medicine. Eur. Polym. J. 2017; 95: 547-565. (DOI:10.1016/j.eurpolymj.2017.08.048)

22. Samadi N., Sabzi M., Babaahmadi M. Selfhealing and tough hydrogels with physically cross-linked triple networks based on agar/PVA/graphene. Int. J. Biol. Macromol. 2018; 107(Part B):2291-2297. (DOI:10.1016/j.ijbiomac.2017.10.104)

23. Tang Y., Pang L., Wang D. Preparation and characterization of borate bioactive glass cross-linked PVA hydrogel. J. Non-Cryst. Solids. 2017; 476:25-29. (DOI:10.1016/j.jnoncrysol.2017.07.017)

24. Pritchard J.G. Poly(vinyl alcohol): Basic properties and uses. London: Gordon & Breach Science. Publ., 1970. P. 16. (https://doi.org/10.1002/pol.1970.110080914)

25. Jia E., Su L., Liu P., Jiang M., Ye G., Xu J. Hydrogen bond and crystalline structure of the junction network in polyvinyl alcohol/dimethysulfoxide gels. J. Polym. Res. 2014; 21(9): Article: 548. (DOI:10.1007/s10965-014-0548-7)

26. Lozinsky V.I., Leonova I.M., Ivanov R.V., Bakeeva I.V. A study of cryostructuring of polymer systems. 46. Physicochemical properties and microstructure of poly(vinyl alcohol) cryogels formed from polymer solutions in mixtures of dimethyl sulfoxide with low-molecular-mass alcohols. Colloid Journal. 2017; 79(6):788–796. (DOI:10.1134/S1061933X17060114)

27. Chemical encyclopedia: in 5 v. Ed. I.L. Knunyants. M.: Sov. Encyclopedia Publ., 1988. V. 1. P. 171-172. (in Russ).

28. Rogozhin S.V., Lozinsky V.I., Vainerman, E.S., Domotenko, L.V., Mamcis, A.M., Ivanova S.A., Shtil´man M.I., Korshak V.V. Non-covalent cryostructuring in polymer systems. Dokl. Acad. Nauk USSR. 1984; 278:129-133. (in Russ)

29. Eldridge J.E., Ferry J.D. Studies of the cross-linking process in gelatin gels. III. Dependence of melting point on concentration and molecular weight. J. Phys. Chem. 1954; 58(11):992-995. (DOI:10.1021/j150521a013)