The synthesis of 4-cyano-4'-(2,2,2-trifluoroethoxy)biphenyl (20CBF(3)) is described and the melting point is found to be 20 degrees C above that of 20CB. The nematic-isotropic transition temperature for 20CBF(3) is determined to be lower than 30 degrees C by extrapolation of the transition temperatures obtained for mixtures with the nematogen I35. The conformational distribution in 20CBF(3) is investigated by analysis with the maximum entropy method of the dipolar couplings obtained from the deuterium-decoupled, proton NMR spectrum of a partially-deuteriated sample dissolved in the nematic solvent ZLI 1132. It is concluded that 20CB and 20CBF(3) have very similar conformational distributions, and that the differences in their phase transition temperatures is probably a consequence of the very different charge distributions in the two molecules.
A comparison between the structure and liquid-crystalline properties of 4-cyano-4'-ethoxy- and 4-cyano-4'-(2,2,2-trifluoroethoxy)-biphenyl
CELEBRE, Giorgio;DE LUCA, Giuseppina;
1996-01-01
Abstract
The synthesis of 4-cyano-4'-(2,2,2-trifluoroethoxy)biphenyl (20CBF(3)) is described and the melting point is found to be 20 degrees C above that of 20CB. The nematic-isotropic transition temperature for 20CBF(3) is determined to be lower than 30 degrees C by extrapolation of the transition temperatures obtained for mixtures with the nematogen I35. The conformational distribution in 20CBF(3) is investigated by analysis with the maximum entropy method of the dipolar couplings obtained from the deuterium-decoupled, proton NMR spectrum of a partially-deuteriated sample dissolved in the nematic solvent ZLI 1132. It is concluded that 20CB and 20CBF(3) have very similar conformational distributions, and that the differences in their phase transition temperatures is probably a consequence of the very different charge distributions in the two molecules.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
