Modifying nanocellulose hydrogels with O-acetylgalactoglucomannan derivatives: tuning the surface hydrophilicity of the fiber surface

Abstract

Cellulose nanofibrils (CNFs) are emerging nanomaterials for such biomedical applications as cell culture platform and biomaterials in context of tissue engineering, thanks to their outstanding properties including bio-renewability, hydrophilicity, excellent mechanical strength and high surface area and aspect ratio originated from their nanodimensions. This current master thesis work prepared CNF via 2,2,6,6- tetramethylpiperidine 1-oxyl radial (TEMPO) oxidation from a birch kraft pulp. The prepared CNF was elaborately characterised with material properties including the dry content, the surface charge density and the contents of reactive carboxylic acid groups and aldehyde groups introduced to the surface. A series of biopolymers of native galactoglucomannan (GGM) and its derivatives with polydimethylsiloxane were used to modify the CNF surface via the specific adsorption of the GGM block in the biopolymers to the cellulose surface. The adsorption of the GGM derivatives to the CNF was quantified by methanolysis in combination with gas chromatographic analysis. Depending on the molecular structure in the GGM derivatives, these hemicellulose biopolymers rendered different wetting properties with adsorption onto the CNF membrane as characterised by contact angle measurements. Using a sequential solvent exchange process and freezedrying method, aerogels were prepared out of all modified CNF membranes. Meanwhile, the adsorption of GGM derivatives onto CNF surface altered the fiber-fiber interactions to endow distinct topographical features compared with that in plain CNF aerogel.