pH‐responsive amine‐based fluorescent polymers with on–off switchable and concentration‐dependent fluorescence behaviors

Abstract

In this paper, pH‐responsive fluorescent poly(amino ether ester)s with reversible “on–off” switching fluorescence and concentration‐dependent emission behavior were reported. A remarkable difference fluorescence behavior was observed at diverse polymer concentrations with pH values. Moreover, at all investigated concentrations, poly(amino ether ester)s can respond to acid pH and exhibit extreme acid‐induced fluorescence quenching phenomenon. Dynamic light scattering and transmission electron microscopy analyses confirmed that the fluorescence quenching phenomenon is due to the aggregation, which was caused by the protonation of tertiary amine groups in poly(amino ether ester)s under extreme acidic conditions. Interestingly, the quenched fluorescence can be completely recovered by adding an alkaline solution, thereby enabling an “on–off” switch function by adjusting the pH value. Most importantly, the pH‐responsive fluorescent poly(amino ether ester)s exhibit good biocompatibility and cellular imaging, and its cellular imaging function is highly sensitive to acid pH. Thus, this study opens a new idea for the preparation of amine‐based fluorescent polymers as stimuli‐responsive fluorescent probe for cellular imaging, drug delivery, and disease diagnostics.

Hydroxyl–yne click polymerization: a facile strategy toward poly(vinyl amino ether ester)s with color-tunable luminescence

“…We performed experimental analyses and validation to further identify the exact fluorophores and elucidate the color-tunable luminescence mechanism of PVAEEs. Three PAEEs ( PAEE1 , PAEE2 , and PAEE3 ) containing only aliphatic tertiary amine groups were synthesized via the t -BuP 2 -catalyzed oxa-Michael addition polymerization of MDEA and diacrylates with different carbon chain lengths at room temperature, 67 and their PL properties were compared with those of the PVAEEs. As expected, all the PAEEs exhibited fluorescence emission, and the red-shifted emission spectra were observed with a decrease in the carbon chain length of the diacrylates (Fig.…”

“…The obtained PAEEs showed low cytotoxicity and bright cell imaging. 66,67 However, this polymerization requires the use of a phosphazene base as a catalyst. Moreover, similar to most unconventional fluorescent polymers, PAEEs exhibit fluorescence in the blue region.…”

Recent progress on polymerization‐induced emission

“…Both hb ‐ and linear‐PAEEs emitted much stronger fluorescence than those of linear and hyperbranched poly(ester ether) without aliphatic tertiary amine, and hyperbranched polymers exhibited much brighter emission than that of linear ones, suggesting that both tertiary amines and hyperbranched structures were the key factors for the fluorescence of hb ‐PAEEs (Figure 15a) [101]. The hb ‐PAEEs also showed good water solubility, specific Fe 3+ ion detection, good biocompatibility, bright cell imaging, and pH‐sensitivity with reversible “on–off” switching fluorescence [102].…”

“…Preparation of luminescent (a) hyperbranched poly(amino ether ester)s ( hb ‐PAEEs) and (b) poly(vinyl amino ether ester)s (PVAEEs) ((a) adapted with permission from Wiley [102]).…”

Rational Design of Stimuli‐Responsive Inorganic 2D Materials via Molecular Engineering: Toward Molecule‐Programmable Nanoelectronics

“…[ 241,443 ] The most employed acidic molecules are those made of carboxylic acids, phosphoric acids, sulfonic acids, or boronic acids. [ 444 ] Otherwise, main basic molecules are those containing in their skeleton N‐rich groups with nonbonding electron pairs, such as amines, [ 445 ] pyridines, [ 446 ] imidazoles, [ 447 ] piperazines, [ 448 ] hydrazones, [ 449 ] pyrrolidines, [ 450 ] and morpholines. [ 451 ] In addition, molecules containing more than one pH‐responsive group (e.g., amino acids like tryptophan, aniline, etc.)…”