Coumarin-substituted pyrrole derivatives with aggregation-enhanced emission characteristics for detecting the glass transition temperature of polymers

Converting natural fluorescent dyes with aggregation-caused quenching (ACQ) properties into functional fluorescent dyes with aggregation-induced emission (AIE) properties has attracted great attention in recent years. Coumarin is a kind of dye widely found in nature and has many excellent optical properties. Based on our group's research on the synthesis and properties of multiarylpyrroles (MAPs), a planar coumarin substituent was introduced into the 1-position of pyrrole to study the effect on the AIE properties of MAPs. The different numbers and positions of phenyl substituents on the pyrrole ring have a significant impact on photophysical properties. Among these compounds, MAP-1, MAP-2 and MAP-4 displayed aggregation-enhanced emission (AEE) properties, while MAP-3 showed ACQ characteristics. In addition, MAP-4 was selected as the AEE luminogen to accurately detect the glass transition temperature (Tg) of polystyrene and polymethyl methacrylate. MAP dyes provide a new method for conveniently and accurately measuring the Tg of polymers.