Aliphatic tertiary amine based hyperbranched polymers with structure-dependent intrinsic fluorescence prepared via self-catalyzed hydroxyl–yne click polymerization

The design and synthesis of aliphatic amine based nonconjugated fluorescent polymers with structure-dependent color-tunable fluorescence property represent a major challenge. It is of paramount importance for understanding the luminescence mechanism of fluorescent polymers to expand their applications. In this study, aliphatic tertiary amine based nonconjugated hyperbranched poly(vinyl amino ether ester)s (HPVAEEs) with color-tunable intrinsic fluorescence were synthesized through the hydroxyl–yne click polymerization of triethanolamine with diynes in the absence of an external catalyst at 25℃. To gain insight into the structures, properties, and their structural relationship with performance of HPVAEEs, we conducted a comprehensive analysis using size-exclusion chromatography, Fourier transform infrared spectroscopy, multidimensional nuclear magnetic resonance, differential scanning calorimetry, thermogravimetric analysis, ultraviolet–visible spectroscopy, and fluorescence techniques. Our findings revealed the successful synthesis of thermally stable HPVAEEs with higher molecular weights and degrees of branching. These HPVAEEs exhibited unique aggregation-enhanced, excitation-dependent, and structure-dependent emission features, predominantly attributable to the aggregation of carbon–carbon double bonds and aliphatic tertiary amine chromophores. It is noteworthy that fluorescence intensity and color of these HPVAEEs were influenced by both internal factors, such as main structure and linear and branched topological architecture, and external factors, including concentration, aggregation state, and excitation wavelength. Thanks to the structure-dependent intrinsic fluorescence, the resultant LPVAEEs and HPVAEEs can be used as security inks for anti-counterfeiting techniques. Furthermore, water-soluble HPVAEEs were prepared by adjusting the monomer ratio, which exhibited low cytotoxicity and enabled multicolor cell imaging. Thus, this study proposes an environmentally friendly and simple strategy to design aliphatic tertiary amines based hyperbranched polymers with structure-dependent color-tunable fluorescence, which has good application prospects in the fields of anti-counterfeiting and cell imaging.