Highly swellable hydrogels were produced by crosslinking of high molecular weight carboxymethylated chitosan (CmCHT) with poly(ethylene glycol) (PEG) oligomers. The hydrogel swelling capacity could be controlled via the crosslinking density and ranged from 900% to 5600%. The hydrogels showed good homogeneity with a high interconnected porosity in the swollen state and with nanodomains rich in CmCHT and others rich in PEG diglycidyl ether. Oscillatory frequency sweep analysis showed a storage modulus of 27 kPa for the hydrogel with the highest crosslinking density, which together with the exhibited enzyme degradability with lysozyme at 59 days indicate that these hydrogels have potential use in delivery systems or soft tissue regeneration.
Rheological properties of the hydrogelsAn oscillatory frequency sweep was carried out to determine the mechanical properties of the hydrogels. Measurements of the shear modulus (G ′ ) were only possible for CmCHT-79 and CMCHT-58 because the other hydrogel samples were too fragile and disintegrated at the beginning of the test. The G ′ values for both samples (Fig. 7(a)) demonstrated that the hydrogel with the highest crosslinking density presented a higher storage modulus value (G ′ = 27 ± 9 kPa for CmCHT-58 and G ′ = 13 ± 6 kPa for CmCHT-79 at 1 Hz). No noticeable changes were observed in G ′ at all sweep frequencies for any sample. The values of the loss modulus (G ′′ ) were lower than G ′ .
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