Filler-Dominated Polymer Nanocomposites: Molecular Transport in Extended Nanocavities

A deeper understanding of the molecular transport mechanisms in filler-dominated nanocomposites is a necessary step toward the development of innovative molecular separation membranes. Nanocomposite membranes were prepared with gas-impermeable Cellulose Nanocrystals (CNCs) at ∼80 wt % content and polyethylene glycol (PEG). Molecular transport takes place according to a configurational diffusion mechanism through extended nanocavities having a cross-sectional size of ∼0.52 nm between packed CNCs. The CO2 solubility-selectivity is favored by physical interaction with the ethylene oxide groups of dispersed PEGs. The PEG chain length affects the CO2 membrane permeability and selectivity, the first one maximized by low-molecular weight PEGs, the latter for polymeric PEGs. © 2026 The Authors. Published by American Chemical Society.