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Thiol-functionalized ESIPT dye in rubber matrices: Mechanically robust, fluorescent, and reversible solid-state pH
Franciela Arenhart Soares1, Magdalena Gaca2, Marcin Kozanecki3
1International Centre for Research on Innovative Biobased Materials (ICRI-BioM)-International Research Agenda, Lodz University of Technology, Żeromskiego 116, 90-924 Lodz, Poland.
Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
|October 24, 2025
Summary
This study introduces novel pH-responsive rubber composites by covalently incorporating a special dye. These functionalized rubbers show potential for developing advanced solid-state optical pH sensors.
Area of Science:
- Materials Science
- Polymer Chemistry
- Chemical Engineering
Background:
- Functionalizing rubbers for sensing is challenging due to dye compatibility and processing issues.
- Existing methods often compromise the inherent properties of elastomers.
- Developing robust, integrated sensing materials is crucial for advanced applications.
Purpose of the Study:
- To develop solid-state, pH-responsive rubber composites.
- To covalently incorporate an excited state intramolecular proton transfer (ESIPT) dye into rubber matrices.
- To assess the dye's stability, the composites' properties, and their pH-sensing capabilities.
Main Methods:
- Synthesized a thiol-functionalized ESIPT dye (HBT-SH).
- Incorporated HBT-SH into butadiene rubber (BR), isoprene rubber (IR), and isobutylene isoprene rubber (IIR) during sulfur vulcanization.
- Characterized dye incorporation using infrared spectroscopy and solvent-release studies.
- Evaluated thermal, mechanical, and optical properties of the resulting composites.
Main Results:
- Successfully achieved stable, covalent incorporation of the ESIPT dye into all tested rubber matrices.
- Composites exhibited strong green fluorescence and distinct responses to acidic and basic vapors.
- BR and IR composites showed reversible fluorescence color changes upon pH variation.
- Minor changes in thermal and mechanical properties were observed, with overall robust mechanical integrity maintained.
Conclusions:
- Demonstrated a scalable method for creating pH-responsive rubber composites.
- The integrated ESIPT dye allows for solid-state optical pH sensing without compromising rubber properties.
- These functionalized elastomers hold promise for developing novel, durable pH sensors.
