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Ice Inhibition Properties of Supramolecular Hydrogels

Sepulveda-Medina, Pablo Ivan
http://rave.ohiolink.edu/etdc/view?acc_num=akron1636623892680971

Abstract Details

2021, Doctor of Philosophy, University of Akron, Polymer Engineering.
The control of ice crystallization is desired in biology, food industries, renewable wind power, and food packaging. Nature has designed countermeasures to control ice crystallization, like antifreeze proteins found in fauna and flora that allowed the biological specimen to survive extreme low-temperature conditions. Antifreeze proteins inhibit ice crystallization by surface absorption into the ice crystal by forming hydrogen bonds between protein hydroxyl groups and water molecules. Another possible mechanism is the confinement of water molecules in the antifreeze protein hydrophobic segments. Due to the low quantity extraction of antifreeze proteins in their native source and inability to be successfully synthesize by bacterial recombination, other forms of ice inhibition technologies have been sought after. Polyvinyl alcohol (PVA) is a synthetic antifreeze protein analog. PVA can inhibit ice nucleation by forming hydrogen bonds between the hydroxyl group of the polymer and ice nuclei. The control of ice crystallization has also been achieved by confining water molecules in rigid materials with well-defined nanoscale porous structures. Nanoscale confinement prevents the alignment of hydrogen bonds into a crystalline structure. The hydrogels polymer network structure size tunability and large water content represent an alternative to rigid porous materials and synthetic antifreeze proteins for antifreeze applications. Modifying the hydrogel chemical composition directly impacts the size of the polymer nanostructure, hydration level, water dynamics, and the degree of ice crystallization of water within the hydrogel. Therefore, it is hard to decouple the water content and ice inhibition properties. In the first part of this dissertation, we demonstrate a route to decouple hydrogel water content and ice inhibition properties by synthesizing copolymer hydrogel using a crystalline hydrophobic crosslinker and kinetically controlled processing of the dry copolymer. We have successfully synthesized a copolymer hydrogel formed from 2-hydroxyethyl acrylate (HEA) and n-octadecyl acrylate (ODA), where ODA is the effective hydrophobic crystalline crosslinker. Thermal control of the ODA hydrophobic crosslinker crystallization process provides a way to modify the microstructure without altering the copolymer chemical composition and hydrogel hydration level. Consequently, controlled kinetic processing of the dry copolymer represents an alternative to enhance the ice inhibition properties in physically crosslinked hydrogels. The physical nature of the hydrophobic crosslinkers was examined in the second part of this dissertation. Two series of copolymer hydrogels with the same hydrophilic component (HEA) but with a crystalline (octadecyl acrylate) or rubbery (ethylhexyl acrylate) hydrophobic component were examined for antifreeze applications. The crystalline crosslinker restricts the polymer network motion. Conversely, the rubbery crosslinker enables a higher degree of freedom in the polymer network. Here we provide a combination of mechanical and structure properties of the hydrogel that directly impact the antifreeze efficacy of these materials. The relationship between copolymer chemistry and dynamics of confined water molecules within hydrogels under freezing temperatures is also investigated. Here we show how the chemistry of the hydrophilic component of a physically crosslinked hydrogel formed from 2-hydroxyethly acrylate and 2-(N-ethylperfluorooctan sulfonamido) ethyl methacrylate (HEA-FOSM) effectively enhances the water self-diffusion coefficient when compared with N,N-dimethylacrylamide -co- 2-(N-ethylperfluorooctane sulfonamido) ethyl acrylate (DMA-FOSA). In summary, control of hydrogel microstructure was achieved without altering chemical composition and maintaining the same hydration level. Mechanical and structure properties were also examined for a rigid and flexible water confinement environment and their correlation to ice inhibition properties. Finally, the water self-diffusion coefficient was improved by altering the hydrophilic chemistry of the copolymer network.
Bryan Vogt (Advisor)
Kevin Cavicchi (Committee Member)
Bi-min Newby (Committee Member)
Fardin Khabaz (Committee Chair)
Mark Foster (Committee Member)
175 p.
Engineering; Physical Chemistry; Polymer Chemistry
Copolymer Hydrogel, Ice inhibition, Small Angle X-ray and Neutron Scattering (SAXS) and (SANS), Wide Angle X-ray Scattering (WAXS), Water Confinement, DSC

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Citations

  • Sepulveda-Medina, P. I. (2021). Ice Inhibition Properties of Supramolecular Hydrogels [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1636623892680971

    APA Style (7th edition)

  • Sepulveda-Medina, Pablo. Ice Inhibition Properties of Supramolecular Hydrogels. 2021. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1636623892680971.

    MLA Style (8th edition)

  • Sepulveda-Medina, Pablo. "Ice Inhibition Properties of Supramolecular Hydrogels." Doctoral dissertation, University of Akron, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1636623892680971

    Chicago Manual of Style (17th edition)

akron1636623892680971
179
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This open access ETD is published by University of Akron and OhioLINK.