Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/17524
Title: Synthesis and characterization of fluorene based oligomers and polymers
Authors: CAI LIPING
Keywords: Fluorene,Conjugated,Oligomer,Polymer,Synthesis,Characterization
Issue Date: 27-Feb-2009
Source: CAI LIPING (2009-02-27). Synthesis and characterization of fluorene based oligomers and polymers. ScholarBank@NUS Repository.
Abstract: Organic conjugated polymers have been thoroughly investigated over the past twenty years due to their promising electronic and optical applications. Current research interests on conjugated polymers focus on tuning their spectral and electrical properties. During these researches, polyfluorene emerged as a very attractive class of conjugated polymers, especially for display applications, owing to their pure blue and efficient electroluminescence coupled with a high charge-carrier mobility and good processability. In our work, four series of fluorene based new polymers and oligomers will be reported. In the work of PPV derivatives polymers synthesis (Chapter two), two novel dichromophore side chains substituted PPV compounds were successfully synthesized. Two key steps in the whole synthesis route were aromatic CH2Br groups¿ protection and deprotection reactions. The high yields of these two reactions were guarantee of the success of whole route. Efficient green light emission, good solubility in common organic solvents, good thermal stability and relative high glass transition temperatures had been demonstrated in these two polymers. These properties made the two polymers good candidates for efficient green light emitting devices In order to investigate the effect of bistricyclic aromatic system on the polymer backbone, two novel tetrabenzo[5.5]fulvalene units containing polymers were successfully synthesized (Chapter three). Good solubility in common organic solvents, good thermal stability and relative high glass transition temperatures had been demonstrated in these two polymers. Although the quantum yield of the two polymers were low due to the good packing of the tetrabenzo[5.5]fulvalene units. These compounds can still have the potential to be used as solar cell and organic field effect transistor materials. Compared with polymers, oligomers generally have more predictable and reproducible properties that are amenable to have optimization through molecular engineering. In our work of Chapter four, five tetra-substituted [2.2]paracyclophane oligomers were obtained in high yields. Two key step reactions, which are HBr gas deprotecting reaction and UV irradiation reaction, gave satisfactory yield of whole synthesis route. Efficient blue light emission, good solubility in common organic solvents had been demonstrated in all of the five compounds. The optical and electrochemical properties all exhibited dependence on the changes of different substituted chromorphores on the [2.2]paracyclophane core. Modification on the substitution groups with different electron-donating and electron-withdrawing groups on the [2.2]paracyclophane core enabled the tuning of HOMO and LUMO energy levels. This freely modification makes the synthesis route very useful to obtain different [2.2] paracyclophanes derivatives which can be used in different applications areas such as asymmetric reaction, OLED and NLO materials. In our last chapter work, a convenient approach to synthesize high steric hindrance hexafluorenyl benzene was successfully established (Chapter Five). Detailed reaction conditions were discussed. This compound can be a theory model of conformational mobile system. In conclusion, by the different synthetic modification, fluorene based polymers and oligomers can be more useful in different materials application.
URI: http://scholarbank.nus.edu.sg/handle/10635/17524
Appears in Collections:Ph.D Theses (Open)

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