A Novel Liquid State of trans-1,2-Dichloroethylene

抄録

The spin-lattice relaxation times (T₁) of trans-1,2-dichloroethylene (trans-DCE), cis-1,2-dichloroethylene (cis-DCE) and 1,2-dichloroethane (EDC) at atmospheric pressure were measured in a temperature region of each melting point to room temperature. Temperature dependences of T₁ of cis-DCE and EDC were those of an ordinary and isotropic liquid, however, T₁-temperature curve of trans-DCE had a “jump” which indicates presence of a liquid-liquid phase transition at −16°C. The liquid state of trans-DCE was divided into two liquid states at this transition temperature as L₁ and L₂ corresponding to the high and low temperature states, respectively.
In the L₁ state, a rotational motion accounts for a large part of the molecular motion as same as other ordinary liquid. In contrast to L₁ the rotational motion is suppressed and the molecules move only translationally in the L₂ state.
The L₂ state is a mesomorphic state which lacks freedom of the molecular rotational motion and is similar to a nematic phase of liquid crystals in this point. A large molecular quadrupole moment of trans-DCE plays an important role in the ordered liquid state.