| 研究実績の概要 |
In the past year, measurement and control of polymer conformation by afm and confocal microscopy were performed. The aim was to examine the origin of the spectral variety observed on single chains of polyfluorene (PFO) and the relation of the green emission to conformation-induced chain aggregation. One approach is based on simultaneous polymer chain stretching by an afm tip and photoluminescence (PL) detection by confocal microscope. For that purpose, polyfluorene end-capped with amine reactive groups was synthesized and characterized. In another approach, nanoparticles of PFO prepared by re-precipitation method, were mechanically pressed by an afm tip and PL response was monitored simultaneously with confocal microscope. The PFO nanoparticles respond consistently to the pressure of the afm tip by strong quenching of PL, which is completely recovered when the tip is retracted. This reversible quenching is accompanied by slight decrease of the intensity of the green PL band. These findings will have important implications in for future flexible devices where PFO is used as an emitter.
Further, PL spectroscopy of neat films prepared from mixtures of two polyfluorene derivatives has been studied. After solvent-vapor annealing of the mixed films which leads to formation of well-ordered beta-phase in PFO, the green PL band completely disappeared due to endothermic energy transfer from the green band to the beta phase. This newly discovered energy transfer mechanism will have important implications in device development involving polyfluorene family of conjugated polymers.
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