Synthesis and characterizations of conjugated polymers based on PEGylated/Alkylated fluorene, benzothiadiazole and carbazole and their water-dispersed fluorescence nanoparticles

In this study, conjugated polymers based on 9,9-disubstituted fluorene, benzothiadiazole and carbazole derivatives were successfully synthesized and fully characterized. Water-dispersed fluorescence nanoparticles of the resulting polymers were also prepared by nanoprecipitation method using different initial concentrations. The polymer nanoparticles are roughly spherical shapes with the average diameter in a range of 56–100 nm. The diameter of fluorescence nanoparticles can be controlled by changing the initial concentrations and the amounts of PEGylated units. In general, the higher initial concentration, the larger diameter can be obtained. In addition, the introduction of PEGylated moieties into polymer side chains can form relatively small particle sizes due to better solubility in aqueous media. Furthermore, the photophysical properties of the polymer particles are dramatically different compared to those of the polymers in solution due to interchain interactions, kinking and bending of densely packed structure. In particular, the presence of lone-pair electrons on the oxygen atoms of the triethylene glycol side chains reduce π-π stacking which leads to hypsochromic shift and enhances the quantum yield of PEGylated polymer nanoparticles.