Design of a graftable triphenylamine-pyridinium-based red fluorescence probe with dual fluorescence emission for quantifying polarity parameters in polymer networks

Fluorescence spectroscopy is a powerful tool for polymer characterization; however, the use of commercial probes is frequently hindered by the UV-visible opacity of the matrices. To circumvent this limitation, a novel reactive push-pull probe was designed, combining a triphenylamine core with a pyridinium and amine group (NH 2 -TPA-Py + ). Through its amine functionality, the probe is covalently grafted within an epoxy-amine network (DGEBA-DDM), thereby eliminating sublimation risks and mitigating self-aggregation (AIE phenomena). This work presents the synthesis and characterization of this probe. It exhibits an intense, red-shifted dual fluorescence (LE and TICT states), which bypasses the internal filter effects of the matrix. After deconvolving the various fluorescence emission signals from the isolated probe and aggregates in different solvents, the use of absorbance and LE and TICT states enables the solvatochromic behaviour of the probe using the Kamlet-Abboud-Taft multiparameter model. This approach was successfully applied to characterize the local polarity ( ), acidity ( ), and basicity ( ) of the network. This work establishes the solution calibration required to convert the dual emission of the probe into local polarity parameters, and applies it to a fully cured DGEBA-DDM network. Extension of this calibration to the in situ monitoring of network ageing is the subject of a dedicated study.