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.

Enzymatic treatment of flax for use in composites

“…Not only tensile properties are scattered, other properties of natural fibers are also highly variable. This distribution in properties can be ascribed to differences in the fiber cultivar itself (composition and structure), influence of different testing methods and testing of fibers on different scales (fiber bundles or elementary fibers) [80].…”

Physical and biological regulation of neuron regenerative growth and network formation on recombinant dragline silks

“…On the other hand, naturally extracted extracellular matrix proteins are usually bioactive and have positive influences on cell growth. However, they suffer from batch-to-batch variations and generally have more undefined components due to the lack of standardized extraction protocols[20, 21]. There is a need for new sources of matrices for tissue engineering that could overcome both the limitations of synthetic and naturally extracted materials.…”

Sorption Thermodynamics of CO2, H2O, and CH3OH in a Glassy Polyetherimide: A Molecular Perspective

“…We present here a theoretical analysis of the sorption of low-molecular-weight penetrants in PEI combined with experimental investigations. The present contribution puts together unpublished results on the CO 2 –PEI system with results on the H 2 O–PEI and CH 3 OH–PEI systems obtained by our group and already reported in recent publications [20,46,47,48]. The aim was to compare the thermodynamic behavior of systems displaying widely different interactive characteristics.…”