Hydrogels are very functional materials suitable for use in biomedical field due to their ability to retain large amounts of water. In recent times a lot of attention is focused on preparation of hydrogels from biopolymers which are biocompatible, bioresorptive and exhibit low toxicity. Ability of biopolymer surface functionalization means that they can be used to prepare smart hydrogels which swell due to external stimuli such as pH value change of their environment.
In this master thesis synthesis of cationic functionalized nanocellulose fibers was performed. With the use of catalyst sodium hydroxide and glycidyltrimethylammonium chloride as cationization reagent, cationic quaternary ammonium salts were introduced on the surface of nanofibers. Successful functionalization of input material was confirmed with the use of infrared spectroscopy. It was also checked if water dispersions of synthesised fibers exhibit hydrogel structure. Quantification of quaternary ammonium salts introduced to fibers surface was carried out using conductometric titration. Based on the results, optimal additions of synthesis reagents were determined to provide the best functionalization of nanocellulose fibers. Using both anionic and cationic nanocellulose fibers, hydrogel mixtures were prepared in a way that mesh size and viscosity of prepared hydrogel mixtures could be influenced. In the scope of this thesis, hydrogels from cationic biopolymer chitosan were also prepared. Chitosan hydrogels were crosslinked with solution of sodium tripolyphosphate to achieve stable hydrogel structure. The degree of crosslinking increased with increasing mass fraction of sodium tripolyphosphate in solution. Rheological characterization of prepared hydrogel mixtures and crosslinked hydrogels was performed. Both viscosity and shear modulus were measured, and hydrogel mesh size was determined for prepared samples.
|
