Liquid crystalline model compounds based on 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA)

3,3′,4,4′-Biphenyltetracarboxylic dianhydride (BPDA) was investigated as the central core unit in mesogenic molecules. Of particular interest was whether the BPDA unit could be self-constrained into a trans-conformation, and thus organize into a liquid crystalline phase. Two homologous series of symmetrical substituted model compounds, 3,3′,4,4′-biphenyltetracarboxy-N-N'-bis-(4-n- alkylphenyl) diimides and 3,3′,4,4′-biphenyltetracarboxy-N-N'-bis-(4-n- alkoxyphenyl)diimides were synthesized. For both series high temperature smectic A phases were observed. To our knowledge these are the first examples of liquid crystalline behaviour observed with BPDA as the mesogenic core.