TEMPO [(2,2,6,6-Tetramethylpiperidin-1-yl)oxyl]-mediated oxidation of bacterial cellulose nanopaper
File(s)
Author(s)
Yang, Yu
Type
Thesis
Abstract
TEMPO [(2,2,6,6-tetramethylpiperidin-1-yl)oxyl] mediated oxidation of bacterial cellulose (BC) nanopaper has been explored. It was found that instead of forming a homogenous suspension of TEMPO-oxidised BC in water, the oxidation reaction produced robust and water stable TEMPO-oxidised BC (TOBC) hydrogels. This is discussed in detail in chapter 3 of this thesis, whereby a pristine BC pellicle was first press-dried into a dried and well-consolidated BC nanopaper, followed by TEMPO oxidation at various NaClO concentrations. The oxidation reaction introduced sodium carboxylate moieties onto the exposed segment of the BC nanofibrils within the nanopaper network structure. This then led to the swelling of the nanopaper into a hydrogel. A swelling ratio of up to 100 times the original thickness of BC nanopaper was observed upon TEMPO oxidation. Neat BC nanopaper, on the other hand, could not swell in water. The water retention value of the TOBC hydrogels was also found to increase with increasing carboxylate content. In chapter 4, this thesis reports that BC nanopaper heat-pressed from pristine BC pellicle at lower temperature is more susceptible towards TEMPO-mediated oxidation. The nanopaper swelling of up 120 times its original thickness when an NaClO concentration of 60 mmol per g and a heat-pressing temperature at 55°C was used. BC nanopaper heat-pressed from BC pellicle at 115°C achieved a swelling ratio of only 20 upon TEMPO-mediated oxidation at an NaClO concentration of 70 mmol per g. The strength of inter-fibril bonding of BC nanopaper was observed to increase with heat-pressing temperature. In chapter 5, self-standing TEMPO-oxidised nanocellulose films fabricated from TEMPO-oxidised BC hydrogel, as well as a homogenous suspension of BC-in-water were compared.
Version
Open Access
Date Issued
2023-03
Date Awarded
2023-12
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Lee, Koon-Yang
Publisher Department
Aeronautics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)