The electrospinnability of Saccharides.
Thesis DisciplineMechanical Engineering
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
The electrospinnability of concentrated aqueous solutions of glucose, fructose and sucrose was combinatorially studied by physicochemical and rheological characterisation methods, and by subsequently examining the fibre morphology via scanning electron microscopy. Furthermore, the significance of intermolecular forces (van der Waals versus hydrogen bonding) in the electrospinnability of saccharides was investigated as a function of the substitution of sucrose (e.g., octa-O-acetyl sucrose and octa-O-methyl sucrose), using an aqueous sucrose solution as the control.
Discussions on secondary bonding driven electrospinnability for saccharide materials are presented throughout the thesis. However, the physical-chemical and molecular mechanisms in the electrospinnability of saccharide materials are still non-obvious.
Furthermore, the electrospinnability of cyclodextrin solutions was also studied in order to explore the effects of hydrogen bonding on supramolecular materials with complex visco- elasticity. Therefore, the electrospinnability of 2-hydroxypropyl-β-cyclodextrins (2HP-β-CD) was investigated by comparing a 2HP-β-CD peroxide-aqueous/acetone-ethanol/NaHCO3 solution and an aqueous urea solution, as a function of 2HP-β-CD concentration. Furthermore, the rheological behaviour of all 2HP-β-CD solutions was characterised by a frequency- independent stress relaxation plateau such as that observed in cross-linked polymer networks and reversible polymer gels with extensive intermolecular bonding.
Moreover, electrospinnability models based on chain entanglement and visco-elasto-capillary theories were compared with experimental results. Visco-elasto-capillary theory showed a better relationship to experimental data, suggesting that longer relaxation times or the capacity to remain electrically stressed for longer periods of time, correlated to improved electrospinnability.
However, neither critical concentration nor visco-elasto-capillary theory can offer an explanation as to how bounded water and aqueous phase separation (aggregate formation) relates to hydrogen bonding or van der Waals interactions during electrospinning.
The commercial application of the research on the electrospinnability of saccharide materials, is exemplified with the development of mānuka honey-glucose syrup nanofibre composite membranes. Commercially sensitive formulations are not reported in this thesis, as products based on the research mentioned on this PhD are currently entering the market.