Monitoring the viscosity in-situ of polymers in real-time remains a challenge as traditional rheological methods can’t be utilized in confined environments. In this study, [Cu(I)(diptmp)2]+ (diptmp = 2,9-diisopropyl-2,4,7,8-tetramethyl-1,10-phenanthroline) was used as an optical probe and incorporated into industrial adhesives. Real-time sensing of viscosity was monitored during the curing process (viscosity increases) via changes in the luminescence of the [Cu(I)(diptmp)2]+. [Cu(I)(diptmp)2] in epoxy glue showed increased emission lifetime of the triplet metal to ligand charge transfer (3MLCT) state in real-time as the glue was cured. To verify the absence of initiator chemical quenching, the real-time viscosity was also monitored reversibly by swelling (viscosity and lifetime decrease) and by unswelling (viscosity and lifetime increase) of the polymer film. Viscosity in opaque samples was also measured which showed a similar correlation of increased luminescence lifetime as the viscosity increased during curing of the adhesive. [Cu(I)(diptmp)2]+ optical probe had higher emission lifetimes and was more ubiquitous as a real-time viscosity sensor in a variety of systems compared to [Ru(II)(bpy)3]2+ (bpy = bipyridine) as a controlled study. These results highlight how the [Cu(I)(diptmp)2]+ optical probe can be used to sense small viscosity changes, including those that are unable to be detected using traditional polymer characterization methods such as rheology.

Real-time and in-situ micro-viscosity monitoring using luminescent Cu(I) phenanthroline complex.

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ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.