W. Mormann, Saria Benadda
Oct 1, 1991
Macromolecular Chemistry and Physics
The first examples of triad diisocyanatodiesters with a substituent in the central aromatic ring, namely methyl-, trimethyl-, tert-butyl-, and phenyl-substituted 1,4-phenylene bis(4-isocyanato-benzoates), and bis(4-isocyanatophenyl) trans-1,4-cyclohexanedicarboxylate are described. The diisocyanatodiesters melt in the range of 160°C, give nematic mesophases and have a clearing transition above 300°C except for the phenyl-substituted diisocyanate which exhibits a monotropic mesophase. Due to the more favourable aspect ratio of the mesogens thermotropic diurethanes were obtained by reaction with butanol and oligomeric thermotropic polyurethanes resulted from the reaction with butanol and diethylene glycol, triethylene glycol, or 3-methyl-1,5-pentanediol. The phase behaviour of the urethanes in relation to their structure is discussed. The thermal stability of the urethanes is limited by the occurrance of urethane cleavage.