Surface morphology regulates the sorption-induced deformation of mesoporous media

Chen, Mingyang; Ke, Liao-Liang

doi:10.1016/j.micromeso.2022.111822

Cited by 1 publication

(2 citation statements)

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“…The shrinkage along the in-plane direction as observed in this study can be explained by the appearance of attractive solid–fluid forces when a rough surface becomes covered with water molecules, as described in the literature . Along the x - and y -directions, this surface stress prevails over the swelling stress induced by the sorption in the matrix, leading to an overall in-plane shrinkage.…”

Section: Resultssupporting

confidence: 69%

“…The shrinkage along the in-plane direction as observed in this study can be explained by the appearance of attractive solid−fluid forces when a rough surface becomes covered with water molecules, as described in the literature. 41 Along the xand y-directions, this surface stress prevails over the swelling stress induced by the sorption in the matrix, leading to an overall in-plane shrinkage. On the other hand, the swelling of the matrix in the z-direction before capillary condensation is dominated by the swelling of the bulk AC and not counteracted by surface effects.…”

Section: ■ Methodsmentioning

confidence: 99%

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Sorption-Deformation Interplay in Hierarchical Porous Polymeric Structures Composed of a Slit Pore in an Amorphous Matrix

et al. 2023

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Prevailing absorbents like wood-derived porous scaffolds or polymeric aerogels are normally featured with hierarchical porous structures. In former molecular simulation studies, sorption, deformation, and coupled sorption-deformation have been studied for single-scale materials, but scarcely for materials where micropores (<2 nm) and mesopores (2−50 nm) coexist. The present work, dealing with a mesoscopic slit pore between two slabs of microporous amorphous cellulose (AC), aims at modeling sorption-deformation interplay in hierarchical porous cellulosic structures inspired by polymeric modern adsorbents. Specifically, the atomic system is modeled by a hybrid workflow combining molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) simulations. The results clarify the multiple sorption/deformation mechanisms in porous materials with different slit-pore sizes, including water filling in micropores, surface covering at the solid−air interface, and subsequent capillary condensation in mesopores. In particular, before the onset of capillary condensation, the sorption behavior of the AC matrix in the hybrid system is almost the same as that of bulk AC, in which sorption and deformation enhance each other through sorptioninduced swelling and additional sorption in the newly created voids. Upon capillary condensation, the interaction between the micropores and the mesopore emerges. Water molecules in the mesopore exert a negative hydrostatic pressure perpendicular to the slab surface on the matrices, resulting in an increase in porosity and water content, a decrease in distance between the centers of mass (COMs) of the slabs, and thus a thinning of the slit pore. As described by Bangham's Law, the surface area of the rough slitpore slab increases proportionally to the surface energy variation during surface covering. For a system composed of a compliant polymer like AC, however, the surface area enlargement does not result in an in-plane swelling as expected but instead in an in-plane shrinkage along with an increase in local roughness or irregularity (an accordion effect).

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Section: Resultssupporting

confidence: 69%

Section: ■ Methodsmentioning

confidence: 99%