Synthesis, Characterization And Fluorescent Sensory Properties Of Fluorescent Conjugated Polymers

Ten new conjugated polymers were designed and synthesized via Heck or Sonogashira coupling polycondensation reaction, which include hyperbranched polymer HTP containing triphenylamine and bipyridine and its linear counterpart (PTP), hyperbranched polymer HTPY and HTPYB containing triphenylamine and pyridine,para-linked poly(p-phenylene ethynylene) type anionic conjugated polyelectrolyte (PPYSA), meta-linked poly(p-phenylene ethynylene) type anionic conjugated polyelectrolyte (PPYSB),para-linked poly(p-phenylene ethynylene) type anionic conjugated polyelectrolyte (PPS), hyperbranched water-soluble conjugated polymer HTBS containing triphenylamine and diacetylene benzene and its linear counterpart (PTBS), water-soluble conjugated polymer/silica nanoparticles (SiO2-PPS). The structure and photophysical properties of all the polymeric materials were characterized. In addition, their properties in the aggregated state and the fluorescent response to metal ions or explosive were investigated.Hyperbranched conjugated polymer HTP and its linear counterpart PTP were synthesized via Pd-catalyzed Heck coupling polycondensation reaction. The polymers were characterized by 1H NMR, FTIR and GPC. Their UV-Vis and photoluminescence (PL) spectra, thermal and electrochemical properties were also examined. The polymers showed good solubility in conventional organic solvents and exhibited good thermal stability. Electrochemical analysis revealed that they exhibited relatively high HOMO energy because of the introduction of triphenylamine unit, and thus could be promising candidates for hole transport materials in solar cells. Hyprebranched polymer HTP showed less chain entanglement and exhibited similar UV-Vis spectra in solid state and solution. In contrast, the linear polymer PTP showed more chain entanglement and its UV-Vis spectrum in film relative to solution exhibited a large bathochromic shift. Furthermore, both polymers showed large Stokes shifts, which could be ascribed to the increased disorder degree resulting from the introduction of triphenylamine unit. It was found that the fluorescence of the polymers in solution can be quenched by various metal ions. The effects of backbone structure of the conjugated polymers on their sensitivity and selectivity have been investigated towards the florescent sensing of metal ions, and the HTP showed higher sensitivity than linear copolymer PTP in the fluorescence response towards transition metal.Hyperbranched conjugated polymers HTPY and HTPYB were synthesized via Heck and Sonogashira coupling polycondensation reactions, respectively. Both polymers were characterized by 1H NMR, FTIR and GPC. In addition, their UV-Vis and PL spectra, thermal and electrochemical properties were investigated. The polymers showed good solubility in conventional organic solvents and exhibited good thermal stability. Their fluorescence responses toward metal ions were investigated. It was found that both polymers showed high sensitivity and selectivity towards Pd2+, and KSV for HTPY and HTPYB were estimated to be 1.16×105 and 2.37×105 M-1, respectively. Specifically, HTPYB exhibited higher sensitivity and better selectivity than HTPY in its fluorescence response, suggesting that rigid molecular chains are beneficial for the selective and sensitive detection of Pd2+ by fluorescence quenching.Two water-soluble fluorescent conjugated polymers PPYSA and PPYSB were synthesized via Sonogashira coupling polycondensation reaction. The polymers exhibited good thermal stability and good solubility in water. Their PL emission properties showed concentration and solvent dependency due to the aggregation of the conjugated polyelectrolyte in water solution. It was found that surfactants affected the aggregation of both polymers, and the polyvinylpyrrolidone (PVP) was proved to exhibit best results in promotion and breaking of the aggregation of both polymers in solution. The fluorescence response of PPYSA and PPYSB were investigated towards metal ions in solution. The results revealed that both polymers showed high sensitivity and good selectivity to Pd2+, and the KSV for PPYSA and PPYSB were 7.64×104 and 3.51×104 M-1, respectively.Hyperbranched conjugated polymer HTBS and its linear counterpart PTBS were synthesized via Sonogashira coupling polycondensation reaction. Both polymers were characterized by'H NMR, FTIR and viscosity measurements. In addition, their UV-Vis and PL spectra were investigated. Both polymers showed good solubility in water, and exhibited concentration and solvent dependency in their PL emissions. The interactions between HTBS and different surfactants revealed the aggregation of the water-soluble hyperbranched conjugated polymer in water solution. The PL emission of HTBS could be quenched by Cd2+and Fe3+, suggesting its potentials as chemical sensors for detection of Cd2+ and Fe3+ ions. The introduction of hyperbranched structure provided more migration pathways for excitons to visit receptor and detect an analyte, leading to higher sensitivity than its linear counterpart.Conjugated polymer-grafted silica nanoparticles SiO2-PPS were prepared by Sonogashira coupling reaction involving a two-step procedure. The resulting conjugated polymer-grafted silica nanoparticles were characterized by FT IR, thermogravimetric analysis, transmission electron microscopy (TEM). UV-vis and PL spectroscopy. TEM images showed that the thickness of fluorescent conjugated polymer were 5-10 nm on the silica nanoparticles. The conjugated polymer-grafted silica nanoparticles are highly fluorescent, and the fluorescent response of the nanoparticles of different sizes towards electrondeficient trinitrotoluene (TNT) in solution was studied by examining how the steady state fluorescence intensity changes with the concentration of TNT. The conjugated polymer-grafted silica nanoparticles showed high sensitivity towards TNT. The concentration of SiO2-PPS had little effect on fluorescence response towards TNT, while the sensitivity increased with decreasing the size of silica nanoparticles. Moreover, SiO2-PPS can be used as fluorescent sensor for the detection of dinitrotoluene (DNT) in solution.