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fbtwitterlinkedinvimeoflicker grey 14rssslideshare1
Congdon, Thomas Richard
Languages: English
Types: Doctoral thesis
Subjects: QD
Animals, plants and bacteria can survive sub-zero environments by using specialist proteins that inhibit ice growth. There has been a great deal of work into trying to understand and exploit these proteins for use in cryopreservation, but several strategies fail as the protein’s mechanism for ice growth inhibition causes ice to grow into needle-like crystals, which cause mechanical damage to the cryopreserved material. A range of studies have shown that this shaping can be removed, without affecting ice growth inhibition activity. Synthetic mimics exist, the most interesting being the simple polymer, poly(vinyl alcohol), which alone amongst other synthetic macromolecules displays ice growth inhibition behaviour. The scientific principles behind ice growth, and the molecules that can inhibit this, are detailed in Chapter 1.\ud \ud Chapter 2 examines how the molecular weight of poly(vinyl alcohol) affects ice recrystallisation inhibition activity, and the importance of hydroxyl sequence, using post-polymerisation modification and co-polymerisation. Chapter 3 details the preparation of well-defined block co-polymers of poly(vinyl alcohol), and confirms the importance of the hydroxyl sequence. These polymers maintained their ice recrystallisation inhibition activity despite the addition of large non-active blocks.\ud \ud Chapter 4 demonstrates the synthesis and utility of a novel multifunctional chain transfer agent, which is used to prepare star polymers. The resultant star-poly(vinyl alcohol) was highly active, and activity profiles of these polymers provided further evidence that the mechanism of ice recrystallisation inhibition by poly(vinyl alcohol) does not involve direct binding to ice. Chapter 5 uses the techniques and methodologies developed in Chapter 2 and applies them to another lesser-known ability of poly(vinyl alcohol); thermoresponsivity.\ud \ud In summary, controlled radical polymerisation of vinyl acetate was employed in a range of different ways to prepare poly(vinyl alcohol) and its various co-polymers. These polymers were then tested for ice recrystallisation inhibition. Due to their well defined physical properties, and advanced architectures, new insights into the nature and mechanisms of their activity were available. This mechanistic understanding, and the materials developed for this thesis, display a great deal of potential in expanding the field of cryopreservation.
  • The results below are discovered through our pilot algorithms. Let us know how we are doing!

    • 3. Synthesis and Ice Recrystallisation Inhibition Activity of PVAblock-PVP Co-polymers 3.1 Chapter Overview 111 3.2 Chapter Introduction 112 3.3i The Synthesis of Block Co-polymers via Living Polymerisation 115 3.3ii The Polymerisation and Chain Extension of PVP Macroinitiators 116 3.3iii The IRI Activity of PVA-b-PVP Co-polymers 122 3.3iv Polymerisation and Chain Extension of PVAc MacroCTAs 127 3.3v The IRI Activity of PVA10-b-PVPn Block Co-polymers 137 3.4 Conclusion 143 3.5 Experimental 145 3.6 References 150
    • 4. Synthesis and Ice Recrystallisation Inhibition Activity of ThreeArm Star-PVA 4.1 Chapter Overview 4.2 Chapter Introduction 4.3i The Synthesis of Multi-arm MADIX Agents 4.3ii The Polymerisation of Vinyl Acetate Using a Trifunctional MADIX Agent 4.3iii The IRI Activity of Well-Defined 3-Arm Star-PVA 4.4 Conclusion 4.5 Experimental 4.6 References
    • 1. Nord, F. F.; Bier, M.; Timasheff, S. N., Investigations on Proteins and Polymers. IV.1 Critical Phenomena in Polyvinyl Alcohol-Acetate Copolymer Solutions. Journal of the American Chemical Society 1951, 73 (1), 289-293.
    • 2. Shiomi, T.; Imai, K.; Watanabe, C.; Miya, M., Thermodynamic and conformational properties of partially butyralized poly(vinyl alcohol) in aqueous solution. Journal of Polymer Science: Polymer Physics Edition 1984, 22 (7), 1305- 1312.
    • 3. Furusawa, K.; Tagawa, T., Adsorption behavior of water soluble polymers with lower critical solution temperature. Colloid Polymer Science 1985, 263 (5), 353- 360.
    • 4. Eagland, D.; Crowther, N. J., Influence of composition and segment distribution upon lower critical demixing of aqueous poly(vinyl alcohol-stat-vinyl acetate) solutions. European Polymer Journal 1991, 27 (3), 299-301.
    • 5. Crowther, N. J.; Eagland, D.; Vercauteren, F. F.; Donners, W. A. B., The temperature dependent contributions of component dyads to the partial molal volumes of a series of poly(vinyl alcohol-vinyl acetate) copolymers in aqueous solution.
    • European Polymer Journal 1993, 29 (12), 1553-1561.
    • 6. Christova, D.; Ivanova, S.; Ivanova, G., Water-soluble temperature-responsive poly(vinyl alcohol-co-vinyl acetal)s. Polymer Bulletin 2003, 50 (5-6), 367-372.
    • 7. Wang, R.-C.; Liu, H.-J.; Tong, J.-G.; Chen, Y., Thermoresponsive poly(vinyl alcohol) derivatives: preparation, characterization and their capability of dispersing gold nanoparticles. Polymer Chemistry 2014, 5 (7), 2417-2424.
    • 8. Wei, L.; Cai, C.; Lin, J.; Chen, T., Dual-drug delivery system based on hydrogel/micelle composites. Biomaterials 2009, 30 (13), 2606-2613.
    • 9. An, Q.; Beh, C.; Xiao, H., Preparation and characterization of thermo-sensitive poly(vinyl alcohol)-based hydrogel as drug carrier. Journal of Applied Polymer Science 2014, 131 (1), DOI: 10.1002/app.39720.
    • 12. Congdon, T.; Notman, R.; Gibson, M. I., Antifreeze (Glyco)protein Mimetic Behavior of Poly(vinyl alcohol): Detailed Structure Ice Recrystallization Inhibition Activity Study. Biomacromolecules 2013, 14 (5), 1578-1586.
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