Uncovering divergent fluorescence of aliphatic polyamides: Synthesis, dual polymerization-induced emissions, and organelle-specific imaging

Abstract Amides, essential structural units to construct aliphatic polyamides, peptides and proteins, have been lately demonstrated with Non-traditional intrinsic luminescence (NTIL). However, diversified compositions, structures and environments in current research render aliphatic polyamides with significant divergences in NTILs and obfuscate the fluorescent nature. Herein, we construct a library of aliphatic polyamides by thiolactone chemistry. This versatile approach equips the resultant polyamides with tunable amide category, amide distribution, and chemical environment, facilitating to uncover the structure-NTILs relationship of aliphatic fluorescent polyamides. Unexpectedly, aliphatic polyamides possess dual Polymerization-induced emissions (PIEs) due to different self or non-self hydrogen bonding interactions, which result in distinct fluorescence quenching effect upon various metal ions. Additionally, in-situ generated sulfhydryl can simplify the hetero-atom doping strategy and regulate the PIEs of aliphatic polyamides by modulating the intermolecular forces among the system or with the environment. Furthermore, the introduction of a piperazine unit provides the resultant fluorescent polyamide with lysosome-specific anchoring, which lights up the organelle. These findings not only elucidate the origin of divergent fluorescence in aliphatic polyamides, but also afford fundamental basis to develop new kinds of aliphatic polymers with controllable fluorescence and functionality.