Isocyanatocyanates and (Iso)cyanatocyanurates Synthesis and Liquid Crystal Thermosets

摘要

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-lc-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.