Isocyanatocyanates and (iso)cyanatocyanurates synthesis and liquid crystal thermosets

Synthesis and liquid crystal properties of a series of trifunctional star-shaped cyanurate rings containing mesogens with trimethylsiloxy-, hydroxy, cyanate- and isocyanate groups and of 4-cyanatophenyl-4-isocyanato benzoate ( 2 ) are described. Urethanes from the isocyanato-cyanurate ( 8 ) and monoalkohols were high-melting monotropic or non-1c-compounds. Cyclotrimerisation of the cyanuratocyanate ( 7 ) in comparison to the parent dicyanate ( 1 ) was studied to prove that the strong increase of isotropisation temperature with conversion was related to the polymer effect and not to the gel point. Cyclotrimerisation of 8 and of the isocyanatocyanate ( 2 ) give networks with identical structure of alternating cyanurate and isocyanurate cross-links, the former with nematic organisation, the latter isotropic, which proves the possibility of kinetic stabilization of a mesophase.