Structural and Mechanical Properties of UV-Photo-Cross-Linked Poly(N-vinyl-2-pyrrolidone)Hydrogels

摘要

Biocompatible poly(N-vinyl-2-pyrrolidone)(PVP)hydrogels have been produced by UV irradiation of aqueous polymer mixtures,using a high-pressure mercury lamp.The resulting materials have been characterized by a combination of experimental techniques,including rheology,small-angle neutron scattering(SANS)electron paramagnetic resonance(EPR),and pulsed gradient spin-echo nuclear magnetic resonance(PGSE-NMR)to put in evidence the relationship between the microstructural properties and the macrofunctional behavior of the eels Viscoelastic measurements showed that UV photo-cross-linked PVP hydrogels present a strong gel mechanical behavior and viscoelastic moduli values similar to those of biological gels.The average distance between the cross-linking points of the polymer network was estimated from the hydrogels elastic modulus.However SANS measurements showed that the network microstructure is highly inhomogeneous,presenting polymer-rich regions more densely cross-linked,surrounded by a water-rich environment.EPR and PGSE-NMR data further support the existence of these water-rich domains.Inclusion of a third component,such as glycerol,in the PVP aqueous mixture to be irradiated has been also investigated.A small amount of glycerol(<3% w/w)can be added keeping satisfactory properties of the hydrogel,while higher amounts significantly affect the cross-linking process