| Scheler, E.; Strohriegl, P.: Three color random fluorene-based oligomers for fast micrometer-scale photopatterning, Chemistry of Materials, 22(4), 1410-1419 (2010), doi:10.1021/cm902254f | |
| Abstract: In this contribution we show that random fluorene cooligomers with photoreactive acrylate units can be prepd. in a simple 1-step Yamamoto synthesis. The acrylate functionalities are preserved quant. under Yamamoto conditions. NMR and Maldi-TOF measurements point to an almost statistical incorporation of the comonomers into the oligomer chain. Maldi-TOF analyses give a further insight into the chain compns., and we found fluorene-only oligomers to be present in low quantities. Thin films of the arom. amine contg. cooligomer show a blue fluorescence, the benzothiadiazole oligomer shows yellow photoluminescence, and the bithiophene oligomer emits orange-red light upon excitation. Compared to pure fluorene oligomers with a HOMO of 5.7 eV the HOMO levels of the TPD and bithiophene derivs. are increased to 5.25 and 5.31 eV, resp., whereas the HOMO level of the benzothiadiazole oligomer is decreased to 5.85 eV. Photolithog. expts. reveal that a careful optimization of the conditions, for example, the choice of the photoinitiator, temp., and irradn. wavelength, leads to well-resolved micrometer sized patterns. A min. feature size of 1 micro m was obtained. Thus we showed that with a simple 1-step Yamamoto coupling oligomers with photo-cross-linkable acrylate groups are accessible. UV irradn. leads to densely cross-linked, insol. networks. Thus these materials are ideal candidates for multilayer as well as patterned semiconducting devices |
