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Kinetics of photochromic reactions in thin polymeric layers
Zeman, Vojtěch ; Weiter, Martin (referee) ; Vala, Martin (advisor)
The thesis is aimed to the study of spiropyrane behavior in polymeric matrix of poly(N-vinylkarbazole) (PVK) and poly[2-methoxy-5-(3´,7´-dimethyloctyloxy)-1,4-fenylenvinylene)] (MDMO-PPV). The photochromic transformation of spiropyrane to its isomeric merocyanine form (SPMC) was studied by absorption and emission spectroscopy. It was found, that photochromic reaction is markedly dependent on the environment. In the PVK polymer, which don’t absorb in the visible region, a high yield of photochromic reaction was achieved. Both, absorption and emission spectrums were observed for this system. From the measurement of time dependencies of the fotochromic reaction, the activation energy of the reverse reaction was determined. A different behavior, particularly in emissive spectrums, was found for the MDMO-PPV polymer doped with spiropyrane. Instead of formation of new band of merocyanine, decrease of the polymer fluorescence was observed. Subsequently, we studied the interaction between the polymeric matrix and the photochromic spiropyrane using fluorescence quenching method. On the basis of energy transfer theory, a critical radius of the fluorescence quenching sphere in solution and in solid was determined.
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Kinetics of photochromic reactions in thin polymeric layers
Zeman, Vojtěch ; Weiter, Martin (referee) ; Vala, Martin (advisor)
The thesis is aimed to the study of spiropyrane behavior in polymeric matrix of poly(N-vinylkarbazole) (PVK) and poly[2-methoxy-5-(3´,7´-dimethyloctyloxy)-1,4-fenylenvinylene)] (MDMO-PPV). The photochromic transformation of spiropyrane to its isomeric merocyanine form (SPMC) was studied by absorption and emission spectroscopy. It was found, that photochromic reaction is markedly dependent on the environment. In the PVK polymer, which don’t absorb in the visible region, a high yield of photochromic reaction was achieved. Both, absorption and emission spectrums were observed for this system. From the measurement of time dependencies of the fotochromic reaction, the activation energy of the reverse reaction was determined. A different behavior, particularly in emissive spectrums, was found for the MDMO-PPV polymer doped with spiropyrane. Instead of formation of new band of merocyanine, decrease of the polymer fluorescence was observed. Subsequently, we studied the interaction between the polymeric matrix and the photochromic spiropyrane using fluorescence quenching method. On the basis of energy transfer theory, a critical radius of the fluorescence quenching sphere in solution and in solid was determined.
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Optické a elektrické přepínání v organických polovodičích
Vala, M. ; Weiter, M. ; Nešpůrek, Stanislav ; Zmeškal, O.
The work deals with tuning of electro-optical properties of polymeric media using reversible light-driven switching of photochromic spiropyran guest molecules. The significant change of dipole moment during the photochromic conversion allows construction of simple switching units. Optical responses of such devices were studied using absorbance and photoluminescence, electrical responses, were detected by impedance measurements.
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