title: Diffusion and molecular interactions in a methanol/polyimide system probed by coupling time-resolved FTIR spectroscopy with gravimetric measurements.
abstract: In this contribution the diffusion of methanol in a commercial polyimide (PMDA-ODA) is studied by coupling gravimetric measurements with in-situ, time-resolved FTIR spectroscopy. The spectroscopic data have been treated with two complementary techniques, i.e., difference spectroscopy (DS) and least-squares curve fitting (LSCF). These approaches provided information about the overall diffusivity, the nature of the molecular interactions among the system components and the dynamics of the various molecular species. Additional spectroscopic measurements on thin film samples (about 2 μm) allowed us to identify the interaction site on the polymer backbone and to propose likely structures for the H-bonding aggregates. Molar absorptivity values from a previous literature report allowed us to estimate the population of first-shell and second-shell layers of methanol in the polymer matrix. In terms of diffusion kinetics, the gravimetric and spectroscopic estimates of the diffusion coefficients were found to be in good agreement with each other and with previous literature reports. A Fickian behavior was observed throughout, with diffusivity values markedly affected by the total concentration of sorbed methanol.
authors.affiliation: Institute of Chemistry and Technology of Polymers, National Research Council of Italy Naples, Italy.
authors.forename: Pellegrino
authors.initials: P
authors.lastname: Musto
authors.affiliation: Department of Chemical, Materials and Industrial Production Engineering, University of Naples Federico II Naples, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Galizia
authors.affiliation: Institute of Chemistry and Technology of Polymers, National Research Council of Italy Naples, Italy ; Department of Chemical, Materials and Industrial Production Engineering, University of Naples Federico II Naples, Italy.
authors.forename: Pietro
authors.initials: P
authors.lastname: La Manna
authors.affiliation: Institute of Chemistry and Technology of Polymers, National Research Council of Italy Naples, Italy.
authors.forename: Marianna
authors.initials: M
authors.lastname: Pannico
authors.affiliation: Department of Chemical, Materials and Industrial Production Engineering, University of Naples Federico II Naples, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Mensitieri
keywords: FTIR spectroscopy; diffusion; methanol; polyimide