Amphiphilic AIE-active copolymers with optical activity by chemoenzymatic transesterification and RAFT polymerization: Synthesis, self-assembly and biological imaging

Recently, various AIE-based materials with new characteristics and functions have been developing for different fields. Many chiral polymers are attracting the research interests for the new multifunctional materials in biomedicine, chiral recognition, etc. In this work, novel AIE copolymers with chirality activity were successfully fabricated for the first time. Firstly, a new fluorescent monomer (R)-THM with AIE effect and chirality activity was firstly synthesized by Suzuki reaction and enzymatic transesterification reaction. The quantum yield of (R)-THM increased to 0.643 from 0.100 of its substrate TBP with remarkable red-shift of emission spectra, which was consistent with their quantum chemical calculations of HOMO and LUMO situations, and its specific optical rotation [α]D25°C was about −9.67°. Subsequently, a series of chiral AIE copolymers of PEG-(R)-THM1 and PEG-(R)-THM2 were prepared via RAFT polymerization of (R)-THM and PEGMA with different feeding ratios. Their molecular weights were about 2.0 × 104 g/mol with narrow polydispersity index (PDI), and the kinetics analysis presented a pseudo-first-order linear procedure. For the molar 24.2%–32.3% feeding ratio of (R)-THM, the actual fraction of (R)-THM in the copolymers PEG-(R)-THM1 and PEG-(R)-THM2 was respectively about 22.3% and 30.2%, and the [α]D25°C value of copolymers PEG-(R)-THM1 and PEG-(R)-THM2 was about −2.51° and −3.74°. The amphiphilic structure of the obtained PEG-(R)-THM make them be easily dispersed in water solution and tend to self-assemble into fluorescent organic nanoparticles (FONs) with 100–150 nm diameter by TEM, and their maximum emission wavelength presented at 495 nm with obvious AIE effect. Moreover, the PEG-(R)-THM FONs had good biological compatibility, desirable low cytotoxicity and good cells absorption effect, which showed the great potential in bioimaging application. [Display omitted] •A novel AIE monomer with chirality activity named as (R)-THM was successfully synthesized for the first time.•The PEG-(R)-THM copolymers had the obvious AIE and chirality properties with a pseudo-first-order linear procedure.•The PEG-(R)-THM copolymers have a promising application in bioimaging field.