Surface Functionalisation and Characterisation of Cellulose Nanocrystals

Cellulose nanocrystals (CNCs) are elongated nanoscale crystalline particles able to be extracted from cellulose. They are noted for their combination of strength, stiffness, low density, and biodegradability, as well as emergent properties, such as forming birefringent liquid crystals. CNCs have found applications as a promising new nanomaterial, used in polymer composites, biocompatible scaffolds and optical materials. All these applications depend on the surface properties of CNCs, therefore reliable quantitative characterisation methods of these properties are required. The chemical groups available at the CNC surface are a function of the extraction process used. For CNCs extracted with sulfuric acid, sulfate half-esters are key to their surface chemistry; for CNCs oxidised with the TEMPO reagent, carboxylic acids are key. Here, the functionalisation of CNCs with the conductive polymer PEDOT and with an amine-terminated polyether were both attempted. Moreover, to understand the results of these attempted functionalisation reactions, characterisation of the targeted surface groups was attempted. Various methods have been developed for characterising these surface groups, with conductometric titration chosen as the main focus of this work. Conductometric titration is attractive for its specificity and apparent simplicity. However, it was observed that the measurements from the titrations were significantly influenced by the addition of NaCl and HCl to the samples. This suggested the method’s sensitivity to conditions had been underestimated in previous CNC literature. Therefore, the conductometric titration of CNCs bearing both carboxylic acid and sulfate half-ester groups was investigated in more detail. Focus was given to how the results of these titrations are affected by the concentrations of NaCl and HCl in the sample. The findings indicate that the measurements from these titrations are strongly dependent on the chosen conditions. Further, the conventional approach of fitting tangent lines to the conductivity plot does not fully capture the effects occurring during these titrations. These insights show the need for nuanced analytical methods for accurate measurements of CNC surface chemistry with conductometric titration. These methods should give particular consideration to measurement conditions and the functional groups on the CNCs.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2025

Author dc:creator

• Teall, Benjamin

Advisor dc:contributor.advisor

• Vignolini, Silvia

• Titration
• Conductometric Titration
• Cellulose
• Cellulose Nanocrystals

Licence

• https://www.repository.cam.ac.uk/bitstreams/9817537c-265c-4fd0-aa68-eed482c6c337/download
• http://purl.org/NET/rdflicense/allrightsreserved

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.121633

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/389876