Diffusion and Release of Molecules in Swelling Polymer Networks

2026-03-05

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Tsz Hung Wong

Jie Ma

Zander Sherburne

Shaoting Lin *

DOI：10.1016/j.eml.2026.102466

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Molecular diffusion within swelling polymer networks critically controls fundamental processes across biological systems and engineering applications. Existing studies typically model molecule diffusivity as either a constant or as a polymer-concentration-dependent variable following non-Fickian transport, which remain largely phenomenological. Here, we use experiments and theory to investigate molecule diffusion and release in crosslinked polymer networks under swelling. Our fluorescent recovery after photobleaching experiments reveal an intriguing size-dependent diffusion-swelling relationship: molecule diffusivity exhibits a concave dependence on swelling ratio for small molecules, and a convex-to-concave transition for large molecules as the polymer network swells. Our molecule release experiments further demonstrate a consistent size-dependent release–swelling relationship. We analyze this transition using a mechano-diffusion theory that establishes the relationship between molecule diffusivity and swelling-induced deformation of the polymer network. Monte Carlo simulations incorporating this diffusion-swelling transition further predict the release of molecules from swelling polymer networks, agreeing well with experimental observations. This work not only establishes a theoretical framework for molecule diffusion and release in swelling polymer networks, but also offers insights into biological processes involving molecule diffusion and release.

Keywords:

Diffusion

Swelling

Polymer networks

Molecular release

Mechano-diffusion theory

Diffusion and Release of Molecules in Swelling Polymer Networks

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