Diffusion and adsorption-desorption phenomena in confined systems with periodically varying medium

• Published in: Chemical engineering science 2021-04, Vol.233, p.116386, Article 116386
• Main Authors: Fernandes, M.C., Lenzi, E.K., Evangelista, L.R., Li, Q., Zola, R.S., de Souza, R.F.
• Format: Article
• Language: English
• Subjects: Adsorption-desorption; Diffusion; Liquid crystals; Modulated medium
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2020.116386

•Diffusion in a confined medium with periodically varying coefficient.•Particles may be adsorbed-desorbed with memory effects.•Kind of bulk modulation determines diffusion regimes.•Model easily connected with confined modulated liquid crystals and other lamellar phases. We study diffusing particles in a confined liquid whose diffusion coefficient periodically varies across the sample. The limiting substrates may adsorb-desorb particles when memory effects are also considered. We show how the bulk modulation (amplitude and number of turns) affects bulk and surface distributions. The diffusing regimes are also studied in terms of the physical parameters governing the system, and we show that, by controlling the modulation (amplitude and frequency) in such limited system, might lead to superdiffusive, usual, or subdiffusive regimes. In other words, increasing the number of turns and the amplitude of modulation changes how the mean square displacement changes over time. Fewer turns with large negative amplitude favors faster diffusion whereas higher number of turns and large positive amplitudes favor slower diffusion. This simple model might help understanding diffusing behavior in modulated and crowded systems such as in cholesteric and smectic liquid crystals and other lamellar systems.