1. Cellulose Nanofibrils Films: Molecular Diffusion through Elongated Sub-Nano Cavities
- Author
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Werner Egger, Roberto S. Brusa, Cecilia Ada Maestri, Tönjes Koschine, Paolo Bettotti, Riccardo Checchetto, Marina Scarpa, and David Roilo
- Subjects
Molecular diffusion ,Materials science ,02 engineering and technology ,Activation energy ,engineering.material ,Permeation ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Thermal diffusivity ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,General Energy ,Penetrant (mechanical, electrical, or structural) ,Polylactic acid ,chemistry ,Coating ,Chemical engineering ,Polymer chemistry ,Nano ,engineering ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
We have studied the kinetics of gas transport through films made of self-assembled cellulose nanofibrils (CNF) by a time-resolved mass spectroscopy technique. Few micrometers thick films deposited on polylactic acid (PLA) substrates act as impermeable barriers for CO2, O2, and N2 and reduce the 2H2 (deuterium) and He permeation flux by a factor of ∼103 with respect to the uncoated substrate. Penetrant transport is controlled by the solution-diffusion mechanism and the coating acts as a diffusive barrier. 2H2 and He diffusivity values are in the 10–10 and 10–9 cm2 s–1 range, respectively, and their migration occurs by thermally activated process with 39 ± 1 and 33 ± 2 kJ mol–1 activation energy. Positron annihilation lifetime spectroscopy analysis indicates that the diffusive path between the packed nanofibrils consists of elongated cavities with cross-sectional size ∼ 0.31 nm. Results evidence that the selective transport of the small size penetrants is due to sieving effects and that small penetrant tran...
- Published
- 2017
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