Uniform micellization: the key to enhanced mechanical strength and swelling efficiency of chitosan hydrogel

The fabrication of hydrophilic porous hydrogel, with high mechanical strength and good uptake capacity is desirable for a broad range of applications such as drug delivery and liquid sensors. The usual methods are limited to the production of structures with high density of covalently crosslinked networks that restricts the polymer chain rearrangement, resulting in non-uniformed pore size distribution. Covalent networks also limit the activity of functional groups and influence the uptake properties of the polymer. In this study, we proposed simple cyclic cryogelation for the fabrication of hydrogels with uniform pore sizes via controlling the micellization and crystal formation. The chitosan based hydrogels ionically crosslinked with 8 % (w/v) of tripoli phosphate sodium (TPP) displayed high Young’s modulus (63 MPa) after cyclic freezethawing. The liquid uptake capacity of the samples treated with 8 % (w/v) TPP solution at pH 4 showed a slight decrease of about 29 % in comparison to that of non-cyclic processed samples (36 %).