title: Thermodynamics of water sorption in high performance glassy thermoplastic polymers.
abstract: Sorption thermodynamics of water in two glassy polymers, polyetherimide (PEI) and polyetheretherketone (PEEK), is investigated by coupling gravimetry and on line FTIR spectroscopy in order to gather information on the total amount of sorbed water as well as on the different species of water molecules absorbed within the polymers, addressing the issue of cross- and self-interactions occurring in the polymer/water systems. Water sorption isotherms have been determined at temperatures ranging from 30 to 70°C while FTIR spectroscopy has been performed only at 30°C. The experimental analysis provided information on the groups present on the polymer backbones involved in hydrogen bonding interactions with absorbed water molecules. Moreover, it also supplied qualitative indications about the different "populations" of water molecules present within the PEEK and a quantitative assessment of these "populations" in the case of PEI. The results of the experimental analysis have been interpreted using an equation of state theory based on a compressible lattice fluid model for the Gibbs energy of the polymer-water mixture, developed by extending to the case of out of equilibrium glassy polymers a previous model intended for equilibrium rubbery polymers. The model accounts for the non-equilibrium nature of glassy polymers as well as for mean field and for hydrogen bonding interactions, providing a satisfactory quantitative interpretation of the experimental data.
authors.affiliation: Department of Chemical, Materials and Production Engineering, University of Naples Federico II Napoli, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Scherillo
authors.affiliation: Department of Chemical, Materials and Production Engineering, University of Naples Federico II Napoli, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Petretta
authors.affiliation: Department of Chemical, Materials and Production Engineering, University of Naples Federico II Napoli, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Galizia
authors.affiliation: Institute for Polymers, Composites and Biomaterials, National Research Council of Italy Pozzuoli, Italy.
authors.forename: Pietro
authors.initials: P
authors.lastname: La Manna
authors.affiliation: Institute for Polymers, Composites and Biomaterials, National Research Council of Italy Pozzuoli, Italy.
authors.forename: Pellegrino
authors.initials: P
authors.lastname: Musto
authors.affiliation: Department of Chemical, Materials and Production Engineering, University of Naples Federico II Napoli, Italy ; IMAST S.c.ar.l. - Technological District on Engineering of Polymeric and Composite Materials and Structures Napoli, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Mensitieri
keywords: NETGP-NRHB model; on-line FTIR spectroscopy; polyetheretherketone; polyetherimide; water sorption thermodynamics