Synthesis of amphiphilic fluorescent polymers via a one-pot combination of multicomponent Hantzsch reaction and RAFT polymerization and their cell imaging applications

Recently, amphiphilic fluorescent polymers based on aggregation-induced emission (AIE) have been attracting much attention for their application in the bioimaging field. In this study, by employing PEGMA and TPB as hydrophilic and hydrophobic segments, respectively, novel amphiphilic polymers with AIE features were successfully prepared via the combination of RAFT polymerization and the Hantzsch reaction for the first time. For the same 25% feed ratio of TPB, the molar fraction of TPB in two-step PEG-DHP1 polymers and one-pot PEG-DHP2 polymers was respectively about 20.2% and 23.5%, and their weight average molecular weights (Mn) were about 21 000 and 25 000 with a narrow PDI. From the 1H NMR analysis, the polymer structure by the one-pot method was similar to that by the two-step method. When the feed ratio was increased to 30%, the molar fraction of TPB in one-pot PEG-DHP3 polymers and the corresponding Mn respectively changed to 27.6% and 20 000. In aqueous solution, the obtained amphiphilic PEG-DHP2 polymers tended to self-assemble into fluorescent organic nanoparticles (FONs) with 100–200 nm size, whose fluorescence spectrum presented the maximal emission peak at 460 nm with the obvious AIE phenomenon. More importantly, as a result of the high water dispersibility, good fluorescence, nano morphology and excellent biocompatibility, the as-prepared polymers are attractive for application in cell imaging.