Polar Acetylenic Liquid Crystals with Broad Mesomorphic Ranges. The Positional Influence of Different C,C-Elements on the Transition Temperatures

Various mesogenic nitriles with inserted dimethylene, trans-vinylene and especially ethynylene units at different positions in the structures of typical nematogens have been prepared and examined with regard to their transition temperatures. The thermal stabilities of the mainly nematic phases for these new compounds were compared with those for the corresponding nitriles lacking these C, C-elements. Nematic thermal efficiency orders are given.