Soft matter in hard confinement: phase transition thermodynamics, structure, texture, diffusion and flow in nanoporous media - topical review

TL;DR

This review explores how spatial confinement in nanoporous media influences the thermodynamics, structure, and dynamics of soft matter, highlighting phenomena like phase transitions, flow, and texture formation with implications for nanotechnology.

Contribution

It provides a comprehensive synthesis of equilibrium and non-equilibrium phenomena of soft matter in nanopores, connecting nanoscale behaviors to bulk properties and applications.

Findings

Confinement alters phase transition behaviors and diffusion in soft matter.

Nanoporous materials enable controlled texture formation during crystallization.

Applications include nanostructure synthesis and advanced material design.

Abstract

Spatial confinement in nanoporous media affects the structure, thermodynamics and mobility of molecular soft matter often markedly. This article reviews thermodynamic equilibrium phenomena, such as physisorption, capillary condensation, crystallisation, self-diffusion, and structural phase transitions as well as selected aspects of the emerging field of spatially confined, non-equilibrium physics, i.e. the rheology of liquids, capillarity-driven flow phenomena, and imbibition front broadening in nanoporous materials. The observations in the nanoscale systems are related to the corresponding bulk phenomenologies. The complexity of the confined molecular species is varied from simple building blocks, like noble gas atoms, normal alkanes and alcohols to liquid crystals, polymers, ionic liquids, proteins and water. Mostly, experiments with mesoporous solids of alumina, carbon, gold, silica, and silicon having pore diameters ranging from a few up to 50 nanometers are presented. The observed peculiarities of nanopore-confined condensed matter are also discussed with regard to applications. A particular emphasis is put on texture formation upon crystallisation in nanoporous media, a topic both of high fundamental interest and of increasing nanotechnological importance, e.g., for the synthesis of organic/inorganic hybrid materials by melt infiltration, the usage of nanoporous solids in crystal nucleation or in template-assisted electrochemical deposition of nano structures.