title: Structural and mechanical properties of UV-photo-cross-linked poly(N-vinyl-2-pyrrolidone) hydrogels.
abstract: 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 gels. 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.
authors.affiliation: Dipartimento di Chimica, Università di Napoli Federico II, Via Cintia, I-80126 Napoli, Italy.
authors.forename: Gerardino
authors.initials: G
authors.lastname: D'Errico
authors.forename: Marco
authors.initials: M
authors.lastname: De Lellis
authors.forename: Gaetano
authors.initials: G
authors.lastname: Mangiapia
authors.forename: Annamaria
authors.initials: A
authors.lastname: Tedeschi
authors.forename: Ornella
authors.initials: O
authors.lastname: Ortona
authors.forename: Sabato
authors.initials: S
authors.lastname: Fusco
authors.forename: Assunta
authors.initials: A
authors.lastname: Borzacchiello
authors.forename: Luigi
authors.initials: L
authors.lastname: Ambrosio
mesh_terms: D004548:Elasticity; D004578:Electron Spin Resonance Spectroscopy; D020100:Hydrogels / Q000737:chemistry*; D009502:Neutrons; D011760:Pyrrolidinones / Q000737:chemistry*; D012542:Scattering, Radiation; D014466:Ultraviolet Rays; D014783:Viscosity
chemical_list: D020100:Hydrogels; D011760:Pyrrolidinones