Conjugated polymers based on polyfluorene derivatives and polypyrrole
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In this thesis, a series of polyfluorene based copolymers have been prepared via Suzuki Coupling for use in light emitting diodes (LEDs). Polyfluorene based polymers are synthesized from different monomers. These polymers are characterized with spectroscopic techniques including FT-IR, UV-VIS, Fluorescence and 1H, 13C NMR. Conjugated polymers are attractive chemical structures inherently allowing charge transport. However, in the solid state, conjugated polymers lack stability and form aggregates. To overcome this problem, conjugated polymers can be converted to insulated molecular wires. This can be achieved by separation of the conjugated polymer chains by a macrocycle. In this study, encapsulation of conjugated polymers is tried with two methods. First method is to encapsulate the polymer main chain by macrocycles. Polypyrrole based polypseudorotaxane is prepared in this way. Pyrrole is complexed with the cucurbituril (CB(6)) and following chemical oxidation by FeCl3 in acidic medium yields the desired polypseudorotaxane. Spectroscopic investigations such as FT-IR, UV-VIS, Fluorescence and 1H-NMR confirm the formation of polypyrrole based polypseudorotaxane. The second method involves the rotaxanation of the polymer side chains. For this purpose, fluorene based monomers are chosen because the 9th position of fluorene can be easily functionalized. After attaching suitable groups to the 9th position of fluorene, the rotaxane formation was attempted via 1,3 dipolar cycloaddition in the presence of CB(6). A white light emitting diode is prepared using a hybrid inorganic and organic material based system. Prepared conjugated polymers were used in white light generation. Good results are obtained with high CRI indices. Also the thermal stability of the conjugated polymers is studied by FT-IR, UV-VIS and Fluorescence spectroscopic techniques under heat exposure.
White light emitting diode