In situ visualizable self-assembly, aggregation-induced emission and circularly polarized luminescence of tetraphenylethene and alanine-based chiral polytriazole

Abstract

This work provides a novel strategy for the construction and characterization of novel luminescent nano/micro architectures and functional thin solid films at the macroscale of chiral aggregation-induced emission (AIE) polymers. By introducing a chiral amino acid pendent into AIE scaffolds, we have prepared chiral polytriazole with the backbone of tetraphenylethene (TPE) and alanine by Cu(I)-catalyzed click polymerization. The chiral polytriazole P(TPE–alanine) product shows a typical AIE property and the capacity to self-assemble into diverse fluorescent nano/micro architectures owing to the induction of the chirality of the amino acid attachments. The nano architectures formed at low concentrations undergo a morphological transition from vesicles, “pear-necklace” to helical nanofibers and microfibers while carefully tuning the concentration or the water content of the polymer solution, as revealed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM) and dynamic light scattering (DLS). The microaggregates formed at high concentrations are monitored using a fluorescence microscope (FM) and it provides simple and direct in situ visualization of the “fluorescent” morphological alteration processes of the assemblies. The fluorescence imaging provides better contrast and characteristic information of the micro fluorescent assemblies which is easily disguised in SEM imaging. It correlates the assemblies of the chiral AIE polymer with its characteristic fluorescence and facilitates a rational design of building blocks to construct the desired fluorescent architectures. The polymer also exhibits good film-forming ability and the film shows efficient solid-state emission, excellent optical transparency and aggregation-induced circular dichroism (AICD) and aggregation-induced circularly polarized luminescence (AICPL). From the nano- to microscale, it is an ideal candidate for the fabrication of novel functional materials for promising applications in optoelectronic devices.