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Highly durable one-component epoxy system through encapsulation of 1- methylimidazole curing agent via efficient thiol-ene click reaction
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DOI：10.1007/s00289-026-06587-z.png)
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Abstract
En 中文
One-component epoxy systems require latent curing agents with both long-term stability and controllable release, yet strategies that mechanistically link network structure to release behavior remain limited. Here, 1-methylimidazole (1MI) was encapsulated using thiol–ene polymerization of 4,4′-bismaleimidodiphenylmethane (BMI) with tunable cross-linking densities. Successful synthesis of the microcapsules was investigated by SEM and OM., while UV–Vis release studies revealed a strong dependence of 1MI release on network density and glass transition temperature. Loosely cross-linked capsules exhibited higher loading and faster release, whereas highly cross-linked capsules offered superior storage stability (> 30 days at 25 °C) without loss of curing efficiency at elevated temperatures and positron annihilation lifetime spectroscopy (PALS) confirmed that the release performance was strongly governed by the shell’s pore structure, where smaller and densely distributed pores in highly cross-linked capsules induced diffusion-controlled, sustained release, while the larger and more open cavities in loosely cross-linked capsules promoted thermally activated segmental motion and faster release. Kinetic modeling further demonstrated that the Korsmeyer–Peppas equation best described the release mechanism, linking anomalous diffusion to segmental mobility above Tg. DSC and DMTA analysis further demonstrated that although microcapsule-assisted curing achieved complete epoxy curing, the presence of flexible capsules reduced Tg and storage modulus due to localized plasticization effects. In addition, the microcapsules exhibited a pronounced plasticizer-like effect on the cured epoxy network, leading to significant changes in the thermomechanical properties of the system. This finding provides rare mechanistic evidence that cross-linking density governs the balance between encapsulation stability and triggered release, establishing a rational design principle for thiol–BMI-based latent curing agents in advanced one-component epoxy formulations.
Keywords:
One-component epoxy
Microcapsule
Thiol–ene click reaction
Latent curing agent
Shelf life
Controlled release
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