Speaker
Description
The interaction of volatile molecules with paper as a complex porous material is governed by coupled transport and sorption processes that are often experimentally indistinguishable when only overall uptake dynamics are considered. In this contribution, we present a strategy to resolve such overlapping processes using the model system of dimethyl sulfoxide (DMSO) vapor interacting with cellulose-based paper. While conventional sorption curves suggest a single effective process, we demonstrate that the release dynamics reveal the presence of at least two distinct molecular populations characterized by markedly different kinetic time scales.
By combining time-resolved uptake measurements with controlled partial desorption experiments, we separate the contributions of a rapidly exchanging population and a strongly retained population. These exhibit characteristic release rates differing by several orders of magnitude (~10⁻⁴ s⁻¹ vs. ~10⁻⁶ s⁻¹), enabling the reconstruction of individual sorption kinetics for each population. This approach allows us to extract process-specific rate constants and activation energies, providing insight into the underlying physical mechanisms.
We interpret the fast population as weakly bound molecules associated with surface interactions and evolving fiber morphology, while the slow population is attributed to molecules trapped within the fiber wall. The results highlight that apparent single-process behavior can mask fundamentally different transport and interaction regimes in porous media. More broadly, the methodology offers a general framework for disentangling simultaneous kinetic processes in complex materials where standard approaches fail.
This work advances the understanding of mass transport in paper and related porous systems, with implications for applications ranging from barrier materials and packaging to functional cellulose-based materials.