Mechanical Properties of Nonequilibrium-Swollen Biopolymer Materials Based on Carboxyalkylated Chitosan Derivatives

A series of nonequilibrium-swollen biopolymer materials based on N-(1,2-dicarboxyethyl) chitosan (DCEC), N,O-(carboxymethyl) chitosan (CMC), N-(2-carboxyethyl) chitosan (CEC) and hyaluronic acid (HA) as carboxyl-containing polysaccharides were obtained. Evaluation of the mechanical strength of the swollen materials under compression showed that the samples of biopolymers based on N-(1,2-dicarboxyethyl) chitosan with a functionalization degree of 0.35, 0.5 and N,O-(carboxymethyl) chitosan with a functionalization degree of 1, were destroyed, probably due to the formation of a denser network of intermolecular interactions. Materials based on hyaluronic acid and N-(2-carboxyethyl) chitosan showed high elasticity and plasticity. However, the biopolymer material based on hyaluronic acid has lower mechanical strength due to its low molecular weight. A sample based on N-(2-carboxyethyl) chitosan with a functionalization degree of 1 is characterized by high mechanical strength and elasticity, with a true stress of 1.24 MPa. This opens the possibility of developing new medical materials based on these biopolymers.