Synthesis and properties of 2-phenylbenzoxazole-based luminophores for insitu photopolymerized liquid-crystal films

16 pages, 5 figures, 4 tables, 2 schemes.We report the synthesis of a series of blue-emitting 2-phenylbenzoxazoles (PBOs) substituted at either the 5- or 6-position of the benzoxazole ring and the para-position of the phenyl substituent. The thermal and optical properties of the materials can be rationalized in terms of the position of the substituent at the benzoxazole moiety and the electron-withdrawing or electron-donating character of the substituents. From the results, we conclude that the combination of an electron-donating substituent at the benzoxazole fragment and an electron-withdrawing one at the phenyl fragment has a more marked effect on the electronic properties of the aromatic PBO core than other possibilities. This particular combination gives luminophores that are suitable for optical applications on the basis of their high emission efficiency and photostability. In view of that, oriented films were prepared by in situ polymerization of a mixture of a liquid crystalline direactive matrix containing 5% (w/w) of the luminophore. The films exhibit linearly polarized emission.Peer reviewe