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. (c) 2008 Wiley Periodicals, Inc.