3.2. Swelling properties of the hydrogels
The influence of the carboxymethylcellulose composition on the swelling ratio of cellulose/CMC hydrogels in distilled water at 37 C is shown in Fig. 6. The samples exhibited high equilibrium swelling ratio, indicating all of the samples were superabsorbent hydrogels. As expected,the equilibrium swelling ratio of the cellulose/CMC hydrogels increased rapidly with an increase in the CMC contents.
This confirmed further that highly hydrophilic carboxyl group of CMC could absorb a lot of water to enhance the space in the hydrogels. In the other hand, cellulose/ NaOH/urea aqueous solution could form irreversible gelation by heating [39], thus physical cross-linking in cellulose also played an important role in the formation of hydogels. So, the entanglements of cellulose chains through hydrogen bonds could occur easily in solutions of high cellulose concentration, leading to the decrease of the equilibrium swelling ratio with an increase of cellulose content. The maximum swelling ratio of the hydrogels was more than 1000, which was clearly higher than that prepared from cellulose derivative [32]. It is important for biodegradable materials to have high swelling ratio for wide application in the biomedical field. To evaluate the suitability of the cellulose/CMC hydrogels as biomaterials, we studied their swelling ratios in different simulated biological solutions. Fig. 7 shows the effects of the D-glucose, urea, physical saline water and synthetic urine solutions on the swelling phenomena of the different hydrogels. All of the hydrogels exhibited the same shrinking behaviors in a given solution, as a result of the inhibition of the electrostatic effects caused by the To evaluate the suitability of the cellulose/CMC hydrogels as biomaterials, we studied their swelling ratios in different simulated biological solutions. Fig. 7 shows the effects of the D-glucose, urea, physical saline water and synthetic urine solutions on the swelling phenomena of the different hydrogels. All of the hydrogels exhibited the same shrinking behaviors in a given solution, as a result of the inhibition of the electrostatic effects caused by the