Synthesis and fluorescent properties of diblock terpolymer micelles modified with an aromatic thioether-based AIE fluorophore

Nghiem, T.-L.; Riebe, S.; Maisuls, I.; Strassert, C. A.; Voskuhl, J.; Gröschel, A. H.

Abstract

Aggregation-induced emission (AIE) is a rapidly evolving field particularly suited for bioapplications including imaging and sensing. We introduce a water-soluble block copolymer/AIE micelle system, in which we incorporate an aromatic thioether-based fluorophore with AIE properties into an amphiphilic diblock terpolymer via covalent post-modification. For that, we synthesized a series of poly(ethylene oxide)-block-poly(styrene-co-hydroxyethyl methacrylate) (PEO-b-P(S-co-HEMA)) diblock terpolymers by atom transfer radical polymerization featuring a hydrophilic PEO block, and a hydrophobic block of PS statistically segmented with HEMA for covalent fluorophore attachment. Synthetic steps were monitored with NMR and IR spectroscopy, mass spectrometry, and gel permeation chromatography (GPC). Self-assembly of the fluorophore-modified block copolymers in water resulted in micelles with fluorescent properties attributed to the immobilized AIEgen within the micelle core. The micelle morphology was analyzed with transmission electron microscopy (TEM) and dynamic light scattering (DLS), while photophysical properties of polymers and micelles were comprehensively investigated with fluorescence spectroscopy. In perspective, the presented diblock terpolymer can be modified with a range of compatible fluorophores, which allows the direct comparison of fluorophore performance in identical assemblies.