New Mesogenic Compounds Containing a Terminal-Substituted Benzoxazole Unit

A series of novel mesogenic 2-(4-alkoxyphenyl-1-yl)-benzoxazole derivatives bearing different substituents (H, NO2, CH3, Cl, coded as nPB-H, nPB-N, nPB-M, and nPB-C, respectively) at the 5-position were prepared and characterized. nPB-N, nPB-M, and nPB-C exhibited enantiotropic smectic mesophases with the mesophase ranges 3 °C–32 °C and 3 °C–82 °C on heating and cooling processes, whereas nPB-H showed no mesophases. The substituents with the stronger electron withdrawing effect let to the wider mesomorphic temperature domain. The nPB-M, nPB-C, and nPB-H displayed intense emission in CH2Cl2 solutions with λmax peaks of the photoluminescence spectra at 350–355 nm when excited at their absorption maxima.