Functionalization of dextran, xylan and nanofibrillated cellulose was performed by first introducing hydroxypropyl azide groups by etherification using glycidyl azide in alkaline aqueous media. The reaction efficiency and degree of functionalization was found to depend on the amounts of reactants, reaction temperature and concentration of the polysaccharide. In the second step, the azide groups were used in copper-catalyzed azide-alkyne cycloaddition reactions for further derivatization. Dextran was grafted with polyethylene glycol and temperature-responsive xylan-based hydrogels were developed by crosslinking reactions using thermoresponsive poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol) block copolymers. In addition, the reaction was applied on surface functionalization of NFC, providing fluorescent 5-(dimethylamino)-N-(2-propyl)-1-naphthalenesulfonamide or pH responsive amine functionalized NFC. Experiments of utilizing the developed amine functionalized NFC in graphene composites were conducted. The composites were found to exhibit good electrical and mechanical properties. In addition, all-cellulose NFC composites were developed. The modification of nanofibrillated cellulose was done by both physical and chemical means, using carboxymethyl cellulose and solid state epoxy chemistry. These composites were produced by tape-casting from aqueous NFC suspensions containing carboxymethyl cellulose. CMC was shown to alter the rheological properties of the suspensions by physical interactions, which allowed the production of anisotropic composites by shear-induced partial orientation of fibrils during tape casting. The CMC also provided carboxyl groups to the composite, which could be used to improve the wet strength of the material though ionic crosslinking using glycidyl trimethylammonium chloride.
|Translated title of the contribution||Dextraanin, xylaanin ja selluloosan nanokuitujen funktionalisointi click-kemialla vedessä|
|Publication status||Published - 2014|
|MoE publication type||G5 Doctoral dissertation (article)|
- chemical modification