SANS Characterization of an Anisotropic Poly(vinyl alcohol) Hydrogel with Vascular Applications

Abstract

Poly(vinyl alcohol) (PVA) hydrogels are formed by physical cross-linking through freeze/thaw cycles. By controlling the stress applied during the freeze/thaw process, anisotropic PVA hydrogels can be produced. An anisotropic PVA hydrogel conduit that mimics the nonlinear and anisotropic mechanical properties displayed by porcine aorta was developed. Preliminary structural characterization of isotropic and anisotropic PVA samples using small-angle neutron scattering reveals a polymer mesh cross-linked by crystallites spaced by about 18 nm and, most importantly, that the anisotropic properties are due to large-scale (>100 nm) structures alone; the geometry of the polymer mesh and crystallites remains largely unaltered. Controlling the properties of these anisotropic PVA hydrogels promises a broad range of potential applications in biomedical devices, such as coronary bypass grafts, where compliance mismatch between the implanted synthetic graft and the surrounding tissue has been identified as a major cause of failure.