부산대학교 도서관

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 N2and reduce the 2H2(deuterium) and He permeation flux by a factor of ∼103with respect to the uncoated substrate. Penetrant transport is controlled by the solution-diffusion mechanism and the coating acts as a diffusive barrier. 2H2and He diffusivity values are in the 10–10and 10–9cm2s–1range, respectively, and their migration occurs by thermally activated process with 39 ± 1 and 33 ± 2 kJ mol–1activation 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 transport occurs in configurational diffusion regime.