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Nyamayaro, Kudzanai

University of British Columbia

The use of bioderived polymers to manufacture functional and sustainable materials for advanced applications is an attractive approach to tackle pollution. Cellulose nanocrystals are an appealing alternative material for applications that have been dominated by petrochemical-based polymers. This thesis focused on the modification of cellulose nanocrystals to enhance their applicability in biodegradable electronics and in rheology modifiers. The rising interest in wearable devices has led to increased research into the development of flexible electronics. Flexible iontronic devices that employ ions as charge carriers have been accessed by employing ionic conducting hydrogels (ICHs). Towards this goal, we created an ICH based on bioderived cellulose nanocrystals (CNCs) for a flexible, biocompatible, and biodegradable ionic diode. The current rectification ratio reached 70 reproducibly, which was significantly higher than analogous diodes generated with microfibrillated cellulose (~15) and the first polyelectrolyte gel diode (~40). The ionic diode was then used to study the mechanism of ionic current rectification. The diode was shown to operate via a physical mechanism that involves the electrochemical generation of proton and hydroxyl ions at the electrodes to generate current. In addition to understanding the mechanism, designing robust ICHs for electronics is essential. The water retention and anti-swelling properties in hydrogels was tuned by incorporating CNCs with different counter ions. In neutral polyacrylamide (PAM) hydrogels, changing from CNC-Na to CNC-Mg and CNC-Al did not influence the extent of anti-swelling while the water retention properties of PAM were significantly changed. In contrast, for ionic conductive Poly(AM-co-SPA) hydrogels, the different CNCs significantly reduced the swelling whereas they did not significantly influence the water retention properties. The rheological properties play a major role in different applications. Rheology was used to investigate the influence of surface characteristics (surface functional groups and counter ion) on the structure of CNC hydrogels. It was demonstrated that CNC suspensions with increased interparticle interactions such as hydrogen bonding and electrostatic interactions form network structures at lower concentration. The varying rheological properties displayed from CNCs with different surface properties help in understanding and predicting the performance of CNC as rheological modifiers in fluid-based applications.

Text; Still Image

2024-09-30

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/85460

Chemistry

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/