An acrylate AIE-active dye with a two-photon fluorescent switch for fluorescent nanoparticles by RAFT polymerization: synthesis, molecular structure and application in cell imaging

Recently, AIE-active fluorescent materials have attracted extensive investigation due to their significant applications in the fields of memory devices, photomodulation, information displays, sensors, and biological imaging. In this contribution, a novel acrylate AIE-active dye of TPMA was successfully synthesized by Suzuki coupling and acylation reaction, and belongs to the monoclinic crystal system and P2(1)/c space group from the crystal structure analysis, and its fluorescence intensity was stronger with an obvious red shift of emission wavelength as compared with the reported TPB dye. Moreover, the obtained TPMA dye exhibits multi-stimuli-responsivity and a two-photon fluorescent switch with excellent reversibility in the solid state. Subsequently, the corresponding fluorescent polymers of PEG-TM were successfully fabricated via RAFT polymerization of TPMA and PEGMA with a molecular weight of about 25 000 (M(n)) and narrow polydispersity index (PDI). From (1)H NMR analysis, when the feeding ratio of TPMA increased to 32.2% from 19.2%, the molar fraction of TPMA in PEG-TM polymers accordingly increased to 32.8% from 19.5%. In water solution, the as-prepared PEG-TM1 polymers would self-assemble into fluorescent organic nanoparticles (FONs) with diameters ranging from 150 to 250 nm, and their maximum emission wavelength presented at 518 nm with obvious AIE phenomena. Moreover, the as-synthesized PEG-TM polymers have prospective application in biological imaging due to their good fluorescence, high water solubility and excellent biocompatibility.