Abstract
Oxidised cellulose nanofibrils (OCNF) prepared from renewable sources of cellulose, one of the largest biopolymers, have applications in various fields. In this thesis research towards developing a sustainable electro-chemical method for the selective oxidation of cellulose to increase the dispersibility of the corresponding OCNF in aqueous solutions is reported, and some potential applications of OCNF explored.Initial work involved developing a facile method for rapid voltammetric screening of mediators, pH and buffer solutions in order to optimise the reaction conditions for electro-oxidation of cellulose. The electro-oxidation of cellulose was optimised based on the voltammetric screening results (using a TEMPO mediator in carbonate buffer at pH 10), and the reaction was accomplished in a comparable amount of time (2-3 h) to that used in the chemical oxidation. The electro-oxidised cellulose particles possessed a similar fibril-like morphology to chemically oxidised cellulose, although higher aldehyde contents were observed (a post-polishing step was required to convert aldehydes into carboxylates).
OCNF were shown to stabilise the hexadecane-water interface without the addition of other emulsifiers, producing Pickering emulsions with oil droplets of ca 2 μm in diameter in the aqueous phase, which remained stable for a period of weeks. The behaviour of OCNF at the oil-water interface under various salt concentrations was explored in situ by small angle scattering, demonstrating that salt addition thickened OCNF shell in the Pickering emulsion, which allowed the release of oil-soluble drug from the emulsion to be controlled. The study showed the potential of OCNF to be developed into an ingredient in cosmetic products and to reduce the use of some irritating surfactants (e.g. sodium lauryl sulfate) in formulations.
Two metal organic frameworks/OCNF (or bacterial cellulose) composites were prepared at ambient temperature via facile synthesis methods, forming self-standing membranes upon drying. [Cu3(benzene-1,3,5-tricarboxylate)2]n was investigated for the CO2/N2 sorption property, and (Ni(NCS)2(para-phenylpyridine)4 was explored for the separation of xylene isomer vapours. The cellulose based composites allow incorporation of selected particles for various applications (e.g. catalysts, purification), while enabling the metals used to be recycled easily after the use of the composites.
| Date of Award | 22 Jun 2016 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Karen Edler (Supervisor) & Janet Scott (Supervisor) |
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