Mechanical and morphological characteristics of poly(vinyl alcohol)/chitosan hydrogels

The effect of freeze–thaw cycles and chitosan type (water‐soluble or insoluble) on the morphological and mechanical characteristics of poly(vinyl alcohol) (PVA)/chitosan hydrogels was investigated with scanning electron microscopy (SEM), uniaxial testing, and a biaxial tubular vessel inflation experiment. SEM images showed that although multiple freeze–thaw cycles had no significant effect on pore size for PVA hydrogels without chitosan, both types of PVA–chitosan hydrogel developed a more porous structure with a greater distribution of pore size. Uniaxial mechanical tests demonstrated decreasing elasticity for successive freeze–thaw cycles within a range comparable to porcine aortic tissue. A conditioning effect, which modified the elastic response of the hydrogels after the first loading cycle, was also shown. Coefficients for hyperelastic material models were determined for the PVA–chitosan (water‐soluble) hydrogels. The internal pressurization and axial extension of a tubular vessel within the physiological range was investigated experimentally and compared with the predictions of a numerical model.