C–H activation/annulation polymerizations of fumaric acid and diynes toward functional fluorescent poly(dilactone)s

The development of C–H activation-based polymerization strategies for the facile and efficient construction of novel functional fused heterocyclic polymers is an important but challenging task. Herein, we report a facile and atom-economical C–H activation/annulation polymerization (CAAP) approach that enables the in-situ formation of unique diheterocycle-fused polymers from readily available monomers based on the C‒H activation of olefins. The rhodium-catalyzed polymerizations of fumaric acid and internal diynes proceed smoothly under mild conditions, producing a series of multisubstituted poly(dilactone)s with high molecular weights (Mw up to 109,600) in moderate to high yields of up to 98.4%. The presence of multiple aryl substituents around the dilactone units endows the resulting polymers with good solution processibility and readily tunable fluorescent properties. Most of the synthesized poly(dilactone)s exhibit aggregation-induced emission (AIE) properties, showing efficient aggregate-state fluorescence. The AIE-active poly(dilactone) can function as a good lysosome-specific fluorescent probe in biological imaging with low cytotoxicity. It is anticipated that these straightforward and economic CAAP reactions together with the structure-property relationship study in this work could promote the exploration of fused heterocyclic polymer materials with more diversified structures and advanced functionalities.