| Summary: | 碩士 === 國立東華大學 === 材料科學與工程學系 === 97 === This research had been study the effect of molecule weight and end-capped in Phase Behavior and Electroptical Properties of conjugated polymers. We choose four sample of Poly[2-methoxy-5-(3,7-dimethyloctyloxy)-1,4- phenylenevinylene] (MO-PPV) that with two different molecule weight and end-capped. We research electroptical properties and topographer of those polymer by HT X-ray diffraction(HT-XRD), Differential Scanning Calorimetry(DSC), UV/Vis Spectrophotometry(UV/Vis), Photoluminonscence spectrometry(PL) and Field Emission Scanning Electron Microscope(FE-SEM). The structure, phase behavior and electroptical properties is similar, but their phase transition temperature are different. All the structure of those sample are lamellar, the d-spacing of as cast sample is about 1.5nm which estimated by XRD, we called it β phase. When the temperature is rising to 80-100 oC, β phase will transition to α phase. The d-spacing of α phase is 2nm and its melt temperature is 320 oC. If it heats over the melt temperature, it will be thermal pyrolysis or crosslink, and become amorphous at cooling step. If it doesn’t heats over melt temperature, the α phase will be retain in the cooling step and the β phase is no more appearance. This result infers that β phase is transient phase or mesopase. The experimental of UV/Vis shows their absorption peak are about 495 nm and bandgap are about 2.14 eV. The wavelength are blue shift at heating. When temperature is heating over melt temperature, the peak of absorption will decrease and can not become initial state. The bandgap of Sample with end-capped DMP is higher than POSS. Higher molecular weight, lower bandgap. The major and minor emission peak of the α phase in PL is about 590 nm and 630 nm, respectively. The wavelength will be blue shift and the major emission peak will decrease when it is heating. At 240 oC, the major emission peak is about 540 nm. When temperature is heating over melt temperature, the peak of absorption will decrease and can not become initial state and the emission peak is similar with β phase. The experiment of FE-SEM shows there are no aggregation at the surface of the as-cast sample. After thermal treatment, we can observe the aggregation had grow up to 40-80 nm in the surface. If the retain time is longer, it will coalesce. As the temperature is rise to 320 oC, the structure is broke down and aggregation is disappearance.
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