Preparation Of Fluorescent Microspheres With Poly(phenylene-vinylene)s As The Fluorophores

Fluorescent microspheres are the solid particles with the fluorescent materials on the surface or inside, having the diameters in the range of nanoscale to micron. They emit fluorescence when excited. Conjugated polymers(CPs) are used as one of the fluorophores for fluorescent microspheres. Conjugated Polymers (CPs) are polymers with delocalizedπelectrons in the polymer backbone. The delocalization of the electrons facilitates the electronic and energy migration along the whole polymer backbone, which make it possible for affect the fluorescence of the whole polymer chain only by a very tiny disturbance from anywhere on the chain. Compared to small molecules, fluorescent CPs can achieve enhanced sensitivity by"million-fold"amplifying of signals. Even higher sensitivity could be achieved in CP aggregates where multi-dimensional energy or electronic migration exists. The fluorescence could be tuned by varying the chemical structures of the backbones, side-chains or adjusting the aggregation structure of conjugated polymer. Here we present a new approach to preparation of fluorescent microspheres with PPV and its derivatives as the shell and the polymer sphere as the core. The sulfonium-salt precursor polymer of PPV and its derivatives were prepared by the Wessling route, which is easy for characterization by FTIR, NMR and GPC. Then they were introduced onto the surface of the host microspheres with negative charged on the surface, through an electrostatic adsorption. The positive charged polymer precursors for PPV or its derivatives were adsorbed onto the negative charged host microspheres. Then the fluorescent microspheres were finally obtained by converting the precursors to PPV and its derivatives through thermal elimination. The properties of fluorescent microspheres were characterized by TGA,FT-IR,UV-Vis absorbance and fluorescence emission. The second and third chapters will discuss about the preparation of PPV-OC₁₂H₂₅ fluorecsent microspheres and PPV fluorescent microspheres, respectively. (1)The sulfonium-salt precursor polymer of PPV-OC₁₂H₂₅ was successfully synthesized by Wessling route, and then converted to PPV-OC₁₂H₂₅ through thermal elimination. The resulting precursor and polymers were very soluble in common organic solvents such as THF and chloroform;It was relatively easy to characterize the resultant PPV and investigate the influence of thermal elimination temperature on fluorescent properties as well as the difference between PPV-OC₁₂H₂₅ solution and PPV-OC₁₂H₂₅ film. Then the precursor polymers were introduced onto the surface of the microspheres through an electrostatic adsorption. The fluorescent microspheres were finally obtained by converting the precursors to PPV-OC₁₂H₂₅ through thermal elimination.(2)Monodisperse fluorescent microspheres with stable emission were obtained by the incorporation of the PPV polymers without side group on the surface of spheres through an similar method metioned above. The properties of fluorescent microspheres were well characterized by TGA,FT-IR,UV-Vis,fluorescence emission,confocal microscopy and flow cytometry. The influence of thermal elimination temperature and time on emission was also studied. Considering the fluorescent stability of the fluorescent microspheres,the sodium polyacrylate polymer layers were introduced onto the surface of the microspheres by LBL, to avoid fluorescence quenching or photobleaching made by environmental impurities.