Broadband dielectric spectroscopy has been used to analyze the temperature, frequency, and concentration dependences of the molecular dynamics of a nematic liquid crystal (5CB) mixed with the nonpolar solvent benzene. Differential scanning calorimetry measurement has been also performed to confirm the phase transitions of 5CB/benzene mixtures. The phase transition temperatures (crystalline to isotropic phases) thus obtained have been described very accurately from the temperature-dependent relaxation strength, the relaxation time, and the symmetric shape parameter of the relaxation function obtained from the fitting procedure. Two relaxation processes reflecting overall rotations around the short and long molecular axes are observed in both the nematic and isotropic phases. In the crystalline phase, the former process with the longer relaxation time disappeared, and latter process with shorter relaxation time shows a discontinuity at the freezing temperature. The relaxation process with shorter relaxation time obtained in the crystalline phase is larger than that obtained in the nematic phase because of the large restrictions in the crystalline phase. For the first time, we have precisely explained the molecular mechanism and structure of liquid crystalline materials as a function of concentration, temperature, and frequency.

Differential scanning calorimetry and broadband dielectric spectroscopy measurements were performed to investigate the phase transitions in nematic liquid crystal (LC)/benzene mixtures. Noticeable changes of the crystal-isotropic phase transition and the phase transition enthalpy were observed. We also estimated the number of unfreezable benzene molecules from the LC/benzene mixtures. The crystal-isotropic phase transition temperature was described very accurately from the temperature-dependent relaxation strength, the relaxation time, and the symmetric shape parameter obtained from the fitting procedure. Surprisingly, the abnormal behavior of the isotropic phase was observed in LC/benzene mixtures that suggested the presence of local structure in the mixture, which set off the dipole moments along the long axis. The interaction between the LC molecules was also discussed from the tau-beta diagram.

We performed dielectric relaxation measurements for 5CB/benzene mixtures in the frozen state at frequencies from 40Hz to 1 OGHz and for liposome/water dispersion systems at frequencies from 300MHz to 20GHz. When 5CB/benzene mixtures take Nematic (N) phase from Isotropic (I so) phase with increasing concentration, the relaxation time distribution parameter, ~. becomes smaller. On the other hand, gelliquid crystal (LC) phase transition for liposome/water system is characterized by a change in the parameter ~ . The ~ value in the LC phase is smaller than that in the gel phase. It is considered that the larger fluctuation of water molecules is realized by interaction between water and lipid molecules in the LC phase with higher mobility. Therefore, dynamical behaviors of LC and liposome in the LC phase are reflected by smaller ~ values with respective molecular mechanisms.