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Quantifying Fluorogenic Dye Hydration in an Epoxy Resin by Noncontact Microwave Dielectric Spectroscopy
Sindhu Seethamraju1,2, Jan Obrzut1, Jack F Douglas1
1Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8542, United States.
The Journal of Physical Chemistry. B
|March 13, 2020
Summary
Chemically modified rhodamine B dye quantifies local water content in epoxy resins. This fluorogenic dye, attached to epoxy backbones, enables precise water measurement using dielectric and fluorescence techniques.
Area of Science:
- Materials Science
- Polymer Chemistry
- Analytical Chemistry
Background:
- Epoxy resins are susceptible to water absorption, affecting their performance.
- Accurate quantification of local water content in polymers is crucial for material characterization and performance prediction.
- Existing methods for water detection in polymers may lack spatial resolution or sensitivity.
Purpose of the Study:
- To develop and validate a chemically modified rhodamine B dye as a sensor for local water content in epoxy resins.
- To combine fluorescence and dielectric measurements for estimating dye-water association.
- To assess the potential of fluorogenic dyes for monitoring interfacial water in epoxy materials.
Main Methods:
- Covalent attachment of a water-sensitive fluorogenic rhodamine B dye to an epoxy resin backbone.
- Photoactivation of the dye using ultraviolet light, leading to fluorescence upon protonation by water.
- High-resolution noncontact microwave cavity dielectric measurements to detect changes in dielectric permittivity.
- Correlation of dielectric changes with dye hydration levels.
Main Results:
- The modified rhodamine B dye exhibits fluorescence upon photoactivation and protonation in the presence of water.
- Photoactivation of the dye resulted in a measurable decrease in dielectric permittivity of the epoxy resin.
- The observed dielectric changes allowed for the determination of the average hydration extent of activated dye molecules.
- A correlation was established between dye fluorescence, dielectric changes, and local water content.
Conclusions:
- Chemically modified fluorogenic rhodamine B dyes are effective sensors for local water content in epoxy resins.
- The combination of fluorescence and dielectric measurements provides a robust method for quantifying water in polymer systems.
- This approach offers a promising solution for monitoring interfacial water, a critical factor in epoxy material performance.
