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Open AccessArticle

Dual Monitoring of Cracking and Healing in Self-healing Coatings Using Microcapsules Loaded with Two Fluorescent Dyes

1
Research Center for Green Fine Chemicals, Korea Research Institute of Chemical Technology, Ulsan 44412, Korea
2
Department of Chemical Engineering, Ulsan National Institute of Science and Technology, Ulsan 44919, Korea
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Author to whom correspondence should be addressed.
Academic Editor: F. Christopher Pigge
Molecules 2019, 24(9), 1679; https://doi.org/10.3390/molecules24091679
Received: 1 April 2019 / Revised: 21 April 2019 / Accepted: 29 April 2019 / Published: 30 April 2019
(This article belongs to the Special Issue Aggregation-Induced Emission: Materials and Applications)
We report the development of an extrinsic, self-healing coating system that shows no fluorescence from intact coating, yellowish fluorescence in cracked regions, and greenish fluorescence in healed regions, thus allowing separate monitoring of cracking and healing of coatings. This fluorescence-monitoring self-healing system consisted of a top coating and an epoxy matrix resin containing mixed dye loaded in a single microcapsule. The dye-loaded microcapsules consisted of a poly(urea-formaldehyde) shell encapsulating a healing agent containing methacryloxypropyl-terminated polydimethylsiloxane (MAT-PDMS), styrene, a photo-initiator, and a mixture of two dyes: one that fluoresced only in the solid state (DCM) and a second that fluoresced dramatically in the solid than in the solution state (4-TPAE). A mixture of the healing agent, photo-initiator, and the two dyes was yellow due to fluorescence from DCM. On UV curing of this mixture, however, the color changed from yellow to green, and the fluorescence intensity increased due to fluorescence from 4-TPAE in the solid state. When a self-healing coating embedded with microcapsules containing the DCM/4-TPAE dye mixture was scratched, the damaged region exhibited a yellowish color that changed to green after healing. Thus, the self-healing system reported here allows separate monitoring of cracking and healing based on changes in fluorescence color. View Full-Text
Keywords: extrinsic self-healing; self-healing detection; aggregation-induced emission; dye-loaded microcapsule; self-healing monitoring extrinsic self-healing; self-healing detection; aggregation-induced emission; dye-loaded microcapsule; self-healing monitoring
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Song, Y.K.; Lee, T.H.; Kim, J.C.; Lee, K.C.; Lee, S.-H.; Noh, S.M.; Park, Y.I. Dual Monitoring of Cracking and Healing in Self-healing Coatings Using Microcapsules Loaded with Two Fluorescent Dyes. Molecules 2019, 24, 1679.

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