Synthesis and mesomorphic properties of 4-alkylamino-4 '-substituted diphenyldiacetylenes

Various substituted aminodiphenyldiacetylenes of the type with X=C3H7, [GRAPHICS] C5H11, F or NO2 and R, R' = H, CH3-C6H13 were synthesized and their mesomor phic properties determined. Semi-empirical and ab initio quantum chemical c alculations using AM1, 421G and 631G* suggested that the amino group would increase the dielectric anisotropy and optical birefringence as compared to the alkyl chain. Mesomorphic properties were found to be poor with the max imum nematic phase range being 44.8 degrees C and many of the compounds hav ing no nematic phase. Both melting temperatures and enthalpies for chose ha ving nematic phases were too high to form good eutectic mixtures.