Hyperbranched Poly(vinyl ether ester)s with Structure-Dependent Intrinsic Fluorescence: Synthesis, Properties, and Applications

In this study, nonconjugated hyperbranched poly(vinyl ether ester)s (HPVEEs) with carbon-carbon double bonds in their backbone were synthesized via bicyclo[2.2.2]-1,4-diazaoctane-catalyzed hydroxyl-yne click polymerization of triols with diynes at 25 °C. Moreover, the branching polymerization behavior, structures, and properties of HPVEEs and the correlation between their structures and performance were analyzed by employing techniques such as size-exclusion chromatography, Fourier transform infrared spectroscopy, nuclear magnetic resonance, differential scanning calorimetry, thermogravimetric analysis, ultraviolet-visible spectroscopy, and fluorescence spectroscopy. Results demonstrated the successful preparation of thermally stable HPVEEs with relatively high molecular weights, high degree of branching, and regular structure in excellent yields through the efficient DABCO-catalyzed hydroxyl-yne branching polymerization. These HPVEEs displayed concentration-enhanced and excitation-dependent emission characteristics, which are attributed to the cluster luminescence generated by the aggregation of carbon-carbon double-bond chromophores. Additionally, these HPVEEs exhibited a unique structure-dependent emission, wherein triols with varied side chains regulated the luminescence quantum yield but not the color; diynes with differing carbon chain lengths could modulate the luminescence color and quantum yield. Remarkably, the polymerization of diynes with other hydroxyl-containing compounds, such as β-cyclodextrin and galactose, resulted in polymers exhibiting low cytotoxicity and bright cell imaging. Thus, this study presents nonconjugated hyperbranched polymers containing unconventional chromophores of carbon-carbon double bonds showing structure-dependent intrinsic fluorescence, which is promising for application in fields such as anticounterfeiting technology and biomedical applications.