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Amphiphilic discotic pentakis (arylethynyl) benzene compounds 1 and 2 containing an enlarged aromatic core functioning as a chromophoric p-electron system were studied with regard to their photophysical properties within Langmuir-Blodgett (LB) films. The results obtained from steady-state absorption as well as fluorescence excitation and emission measurements will be discussed with regard to interchromophoric interactions in the LB films. Time-resolved fluorescence inves6igations revealed the formation of a ground-state complex as well as excimer formation. Thermal treatment causes irreversible destruction of the LB film structure of the discotic amphiphiles. Within droplets the reorganization of the original nematic-discotic (ND) mesophase of the bulk materials was found for the alcohol 2 as indicated by a Maltese Cross texture, whereas the acid 1 remained isotopic.
Langmuir-Blodgett(LB) multilayers were prepared from disc-shaped multiyne mesogens based on amphiphilic alkyl pentakis(aryl-ethynyl)benzene ethers. The two compounds used are characterized by five hydrophobic flexible chains and one hydrophilic substituent at the terminal position of the alkoxy chain. The LB films were analysed by X-ray scattering and spectroscopic measurements. An edge-on arrangement of the two discotic pentaalkynes within Y-type bilayers with a different packing density proved to be possible for the LB films of both compounds.
The structure of mono- and multilayers of amphiphilic disc-shaped pentaynes wa inbestigated by Brewsterangle microscopy, X-ray specular reflection and grazing incidence diffraction (GID). X-ray specular reflection experiments confirm the "edge on" arrangement of the molecular discs. The molecular modelling of the Langmuir-Blodgett (LB)- multilayers predicts a columnar in-plane packing of the molecules. A GID experiment with monochromatic synchrotron radiation was used to verify the predicted multilayer structure on molecular level, while the Brewsterangle microscopy gave a deeper insight in the monolayer in-plane structure on micron scale.