Light-driven fluorescence enhancement of phenylazo indazole-terminated polystyrene

The well-defined phenylazo indazole-terminated polystyrene (PS) was successfully prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene (St) mediated by a novel chain transfer agent (CTA) bearing phenylazo indazole moieties in the Z group, benzyl-5-(4-(dimethylamino)phenylazo) indazole-1-carbodithioate (BPCD). The fluorescence emission of BPCD and the phenylazo indazole-terminated PS in chloroform (CHCl₃) before and after the 365 nm ultraviolet irradiation was investigated. Interestingly, the fluorescence intensities of BPCD and the phenylazo indazole-terminated PS in CHCl₃ were both sensitive to the 365 nm ultraviolet irradiation. The fluorescence intensities of these solutions increased with the irradiation time and reached maximum at 110 min. The light-driven fluorescence enhancement of BPCD and the phenylazo indazole-terminated PS were both attributed to the formation of spherical aggregate originated from the trans-cis isomerization of azobenzene moieties in BPCD and PS chain, which was confirmed by transmission electron microscopy (TEM), ¹H NMR, UV and dynamic light scattering (DLS) spectra.