Dielectric properties of PVA cryogels prepared by freeze–thaw cycling

Solutions of polyvinyl alcohol (PVA) in water can form gels upon repeated freezing and thawing. These PVA cryogels have applications as biomaterials, including artificial tissue and drug delivery systems. We have studied the dielectric properties of PVA cryogels within the freeze–thaw cycles as a fu...

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Bibliographic Details
Published in:The Journal of chemical physics 2020-07, Vol.153 (4), p.044901-044901
Main Authors: Getangama, Nuwansiri Nirosh, de Bruyn, John R., Hutter, Jeffrey L.
Format: Article
Language:English
Subjects:
Artificial tissues
Biomedical materials
Cold Temperature
Critical temperature
Cryogels - chemistry
Dielectric properties
Dielectric relaxation
Drug delivery systems
Freeze thaw cycles
Freezing
Gels
Materials Testing
Polyvinyl alcohol
Polyvinyl Alcohol - chemistry
Temperature dependence
Thermal cycling
Thermodynamics
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Summary:Solutions of polyvinyl alcohol (PVA) in water can form gels upon repeated freezing and thawing. These PVA cryogels have applications as biomaterials, including artificial tissue and drug delivery systems. We have studied the dielectric properties of PVA cryogels within the freeze–thaw cycles as a function of both frequency and temperature in order to understand the physical changes that take place during the thermal cycling process. Our results indicate that most of the changes in dielectric properties occur during the cooling phase of the first cycle and suggest that the solution must be cooled below a critical temperature of about 263 K for the formation of a gel that persists after thawing. The material’s dielectric spectrum shows the presence of several relaxation processes. We identify one of these with the dielectric relaxation of ice and two others with motions of the PVA polymer chains. The temperature dependence of the polymeric relaxation times suggests that they are both thermally activated, with an activation energy of roughly 300 kJ/mol.
ISSN:0021-9606
1089-7690
DOI:10.1063/5.0007251