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.