Synthesis Of Two New Fluorescent Conjugated Polymers And Their Analytical Applications To Nonionic Surfactants

Fluorescent Conjugated Polymers (FCPs) are one ofπ-conjugated linear polymers. They have gained more attention in recent years, and have been widely applied in fluorescent sensing fields because of their unique properties. In this work, two new conjugated polymers, i.e. poly [2, 5-bisnonyloxy-1, 4-phenylene-ethynylene-9, 10-anthrylene] (PPEA) which is hydrophobic, and the water-soluble conjugated polymer, poly [2, 5-di(propyloxysulfonate)-1, 4-phenylene-ethynylene-9, 10-anthrylene] (PPEASO3) were synthesized based on sonogashira palladium-catalyzed cross-coupling reaction, and characterized by 1H NMR, 13C NMR, FTIR, gel chromatography, fluorescence and absorption spectra.Then, we investigated the fluorescence behaviors of PPEA and PPEASO3 in different surfactants. The results showed that the PPEA can be used as a probe for the determination of Triton X-100 and its CMC with high selectivity. Meanwhile, as molecular light switch, PPEASO3 with the large emission change can provide a direct indication for critical micelle concentration of nonionic surfactants. The thesis consists of five chapters as following:In chapter 1, reviews were given firstly on the basic conception, properties, categories and analytical fields of fluorescent conjugated polymers in recent years. Then, the purpose and significance of this study has been illustrated.In chapter 2, the hydrophobic conjugated polymer (PPEA) and the near-infrared water-soluble conjugated polymer (PPEASO3) were prepared and characterized. In chapter 3, the interaction between PPEA and different surfactants was investigated. The fluorescence was dramatically quenched in aqueous solution. However, the fluorescence gradually enhanced with the increasing of the concentration of TX-100. Also, the fluorescence intensity was proportional to the concentration of Triton X-100 in the range of 0-200μmol/L and 200-700μmol/L, respectively. And the concentration corresponding to the point of intersection of the two calibration graphs was found to be in good agreement with the Critical Micelle Concentration (CMC) of Triton X-100. Therefore, a fluorescence enhancement method based on fluorescent conjugated polymer has been developed. It can be used to selectively detect Triton X-100 in the presence of other surfactants and indicate the CMC of Triton X-100.In chapter 4, the fluorescence behavior of near-infrared water-soluble conjugated polymer was studied. It was found that the fluorescence emission of PPEASO3 at 670 nm was quenched due to its self-aggregation in water and aqueous solution containing a low concentration (below the critical micelle concentration, CMC) of nonionic surfactants. However, a dramatic fluorescence enhancement with a large emission blue-shift (> 40 nm) was found once the concentration of nonionic surfactants reached the CMC (especially Triton X-100). An orange fluorescence could be observed even with naked-eyes under UV-lamp, which gave a direct indication for the micelle forming process and provided a simple method for the CMC determination of the nonionic surfactants.In chapter 5, traits and innovations of the thesis were summarized. An outlook of further research was given.