Synthesis And Characterization Of Novel Conjugated Organic Materials

A series of fluorene-based conjugated polymers and oligomers have been designed and synthesized in the dissertation. These compounds are used for the research on electron-transporting materials, light-emitting materials and self-assembly behaviors respectively.In the first work, we focus on developing novel electron-transporting materials for OLED devices, so we design and synthesize a series of conjugated polyfluorene derivatives (PFs) based on fluorene, oxadiazole and benzothiadiazole units. All the PFs exhibit good solubility in common organic solvents, good film-forming property and high thermal stability. In addition, the photophysical properties of these PFs in dilute solution and in solid film are studied in detail. Such as the two series of PFFO and PFFT polymers, they show different characteristic. As for PFFT polymers, the absorption spectra both in dilute solution and in film exhibit two peaks attributed to fluorene and benzothiadiazole units respectively. Additionaly, the absorption of fluorene unit show blue shift with the increasing content of benzothiadiazole in the polymer's main chain. Their emission spectra show two peaks in the blue and green region in dilute solution, and the efficiency of energy transfer from fluorene fragment to benzothiadiazole fragment is improved with the increasing content of benzothiadiazole in the polymer's main chain. While in the thin film, the energy transfer in these polymers is very efficient. Both POFA-ION and PTFA-ION have good solubility in methanol, which could avoid destroying the underlayer. Their photophysical properties are similar with the two series of PFFO and PFFT polymers. Differently, due to repulsion interaction between ions in PTFA-ION, the efficiency of interchain energy transfer is affected to an extent. In addition, both POFA-ION and PTFA-ION have large electron affinity, which have potential applications as electron-transporting materials.In the second part, we focus on improving the stability and color purity of OLED device, by using the nanocomposites made of nanocrystals and conjugated polymers as light-emitting layer. So we design and synthesize a series of conjugated polymers and oligomers with the groups that can bind with nanocrystals in their side chains. As for the series of PFH-NH2F polymers, both of them have high thermal stability, good film-forming and large energy gap. The nanocomposites made of PFH-NH2F-39-1 and core-shell CdSe-ZnS nanocrystals are used as light-emitting layer, and corresponding OLED devices are fabricated by spin coating technology. The result of electroluminance spectra reveal that efficient energy transfer exchange from the polymer to nanocrystal results in bright red light emission (30 nm FWHM) atλmax = 626 nm using a voltage of 5 V. In addition, our QD-OLEDdevice posess long life-time and good stability, and show great promise in providing excellent color stability and device robustness.In the third part, in order to study the self-assembly behaviors of conjugated system, we design and synthesize several conjugated polymers and oligomers. Among these compounds, three conjugated oligomers with hydrogen bond can form one-dimensional nanowires or nanorods, which reveal that hydrogen bond and ?-? stacking play an important role in forming microscopic morphologies. PF-NH2 can form different morphologies in different solvents, and its salt form has good solubility in methanol. We can get pure blue emission using PF-NION as light-emitting layer. PF-Crown can realize self-assembly behavior with amine salt to form polypseudorotaxane in CH2Cl2, while the process doesn't happen in CHCl3. The data of dynamic light scattering reveal that different degree of aggregation in CH2Cl2 and CHCl3 have some affection on self-assembly behavior of PF-Crown with amine salt.