Role of Sulfate Half Ester Groups on Modifications and Network Formation of Cellulose Nanocrystals

Doctoral thesis, 2023

Cellulose nanocrystals (CNCs) are nanomaterials with unique mechanical, physical, and chemical properties, which make them suitable as films and foams. To tap into the potential of CNCs and develop materials with tailored properties and a wider range of applications, it is essential to overcome existing challenges. These include surface-specific chemical modification, detailed analysis of functional groups, and stable CNC dispersion in water without aggregation. The present doctoral thesis addresses these challenges by investigating the role of sulfate half-ester groups, found on CNC surfaces, and in the chemical or enzymatic oxidative modification of CNCs. Moreover, the thesis explores the properties of CNC networks in water suspensions and as part of gel matrices. The results reveal that sulfate half-ester groups, which are negatively charged and bulky, have varied effects on oxidation reactions, highlighting the need to consider functional groups when working with nanomaterials. Furthermore, the thesis emphasizes the importance of analyzing both solid and soluble products for accurate conclusions. The work presented herein also illustrates the methods used to modify the CNC-CNC interaction governed by sulfate half-ester groups. The findings in this thesis advance our knowledge of CNC modifications, as well as our understanding of the mechanisms underlying CNC network formation. This will contribute to the development of green nanotechnologies rooted in nature's renewable resources.