It has been shown that the temperature behavior of dielectric permittivity ($\varepsilon$) in the isotropic phase of nematogens can be described in the same way as in critical binary solutions. Hence, using a relation with the critical exponent $\phi =1-\alpha =0.5\mathrm{}\pm 0.03$ it was possible to portray the results of $\varepsilon \mathrm{}\left(T\right)\mathrm{}$ measurements in the isotropic phase of 5-heptyl-2-(4′-cyanobiphenyl)-pyrimidine and 4,4-$n$-octylcyanobiphenyl. The influence of the position of the permanent dipole moment on the results was tested by additional measurements in $n$-($p$-methoxybenzylidene)-$p^{\prime }$-butylaniline. It also has been shown that a fluidlike analogy can be applied to the nonlinear dielectric effect (NDE), which describes changes of dielectric permittivity induced by a strong electric field. Measurements were conducted for the lowest frequency used in NDE studies ($f=67\mathrm{}$ kHz), so the condition $\tau f\ll 1$ (with $\tau$ the relaxation time) was always fulfilled. Values of discontinuities of the isotropicnematic phase transition from both the analysis of $\varepsilon \mathrm{}\left(T\right)\mathrm{}$ measurements and NDE studies are in good agreement.

Results of studies of static dielectric permittivity (ɛ) and nonlinear dielectric effect (NDE) in the isotropic phase of 4-n${-4\mathrm{}}^{\prime }$-isothiocyanatobiphenyl $\left(n\mathrm{BT}\right)$ homologous series from $n=2\mathrm{}$ to $n=10\mathrm{}$ exhibiting the isotropic-smectic E $(I-\mathrm{S}\mathrm{m}E)$ transition, are presented. They are compared with results of similar studies in 4-cyano-4-n-alkylbiphenyls $\left(n\mathrm{CB}\right)$ from $n=4\mathrm{}$ to $n=12.\mathrm{}$ In this homologous series isotropic-nematic $\mathrm{}(I-N)\mathrm{}$ and isotropic-smectic-A $(I–\mathrm{Sm}-A)$ transitions take place. Despite significant differences between N, $\mathrm{S}\mathrm{m}-A,$ and $\mathrm{Sm}-E$ phases the same pretransitional behavior of ɛ and NDE in the isotropic phase, described by critical exponents $\gamma =1\mathrm{}$ and $\alpha =0.5,$ was found. It has been shown that when the length of the alkyl chain of a compound increases the discontinuity of the transition drops in $n\mathrm{BT}$ and rises in $n\mathrm{CB}.$ The influence of pressure on the discontinuity is also discussed.

The dynamics of glass is of importance in materials science but its nature has not yet been fully understood. Here we report that a verification of the temperature dependencies of the primary relaxation time or viscosity in the ultraslowing/ultraviscous domain of glass-forming systems can be carried out via the analysis of the inverse of the Dyre-Olsen temperature index. The subsequent analysis of experimental data indicates the possibility of the self-consistent description of glass-forming low-molecular-weight liquids, polymers, liquid crystals, orientationally disordered crystals and Ising spin-glass-like systems, as well as the prevalence of equations associated with the 'finite temperature divergence'. All these lead to a new formula for the configurational entropy in glass-forming systems. Furthermore, a link to the dominated local symmetry for a given glass former is identified here. Results obtained show a new relationship between the glass transition and critical phenomena.

The derivative-based analysis for detecting regions of the validity of the Vogel-Fulcher-Tammann (VFT) dependence for superpressed and supercooled liquids is discussed. For the temperature $\left(T\right)$ path the analysis introduced by Stickel et al. [J. Chem. Phys. 104, 2043 (1996); J. Chem. Phys. 107, 1086 (1997)] is recalled. For the pressure $\left(P\right)$ path the derivation based on the counterpart of the VFT dependence proposed in Paluch et al. [J. Phys.: Condens. Mater 10, 4131 (1998)] is presented. The appearance of two ideal glass temperatures $\left(T_0\right)$ or pressures $\left(P_0\right)$, fragility strength coefficients $(D_T,D_P)$, and prefactors $({\tau }_0^T,{\tau }_0^P)$ for VFT equations in following dynamical domains, i.e., high-temperature $\left(\mathrm{\Delta }{T}_{high}\right)$ and low-temperature $\left(\mathrm{\Delta }{T}_{low}\right)$ or low-pressure $\left(\mathrm{\Delta }{P}_{low}\right)$ and high-pressure $\left(\mathrm{\Delta }{P}_{high}\right)$, is stressed. It is noteworthy that the values of $T_0\left(\mathrm{\Delta }{T}_{high}\right)>T_0\left(\mathrm{\Delta }{T}_{low}\right),D_T\left(\mathrm{\Delta }{T}_{high}\right)⪡D_T\left(\mathrm{\Delta }{T}_{low}\right)$, and ${\tau }_0^T\left(\mathrm{\Delta }{T}_{high}\right)⪢{\tau }_0^T\left(\mathrm{\Delta }{T}_{low}\right)$. Analogous behavior was noted for isothermal $\mathrm{\Delta }{P}_L$ and $\mathrm{\Delta }{P}_H$ dynamic domains. A similar derivative-based approach is also applied to test the validity of the mode coupling theory (MCT) critical-like equation $\tau \left(T\right)\propto (T-T_X{)}^{-\mathcal{g}}$. It yields the temperature $T_X$ and the MCT power (“critical”) exponent $\mathcal{g}$ exclusively from the simple linear regression. The extension of such an analysis for the pressure path is also given. The hardly discussed question of the error of estimations of $\mathcal{g}$ and $T_X$ is emphasized. The relation between the derivative based behavior mentioned above and the apparent activation enthalpy (temperature path) or the apparent activation volume (pressure path) is indicated. The presented analysis was applied to discuss the dynamic crossovers in supercooled and superpressed diethyl phthalate, based on experimental data supplemented by those given in Pawlus et al. [Phys. Rev. E 68, 021503 (2003)].

Results are presented of temperature and pressure studies of static dielectric permittivity (ɛ) and the nonlinear dielectric effect (NDE) in the isotropic phase of smectogenic n-cyanobiphenyls: 9CB, 10CB, and 12CB ${(4-\mathrm{c}\mathrm{y}\mathrm{a}\mathrm{n}\mathrm{o}-4\mathrm{}}^{\prime }$-n-alkylbiphenyl, $n=9,$ 10, and 12). For the mentioned properties, pretransitional effects can be well portrayed by applying the relations used for the isotropic phase of nematogens, where evidence of the quasicritical, fluidlike behavior with exponents $\alpha \approx 0.5$ and $\gamma =1\mathrm{}$ exists. This kind of behavior one can also observe on approaching the isotropic–smectic A transition. NDE studies in 10CB and 12CB made it possible to determine the pressure evolution of the discontinuity $\left(\Delta T\right)$ of the $I-\mathrm{Sm}A$ transition. It was found that pressure first decreases the discontinuity of the transition, and that next a gradual rise appears. This behavior is unlike the one observed for the isotropic-nematic transition, where only an increase of $\Delta T$ with rising pressure was observed.

Despite decades of studies on the grand problem of the glass transition the question of well-defined universal patterns, including the key problem of the previtreous behavior of the primary (structural) relaxation time, remains elusive. This report shows the universal previtreous behavior of the apparent fragility, i.e. the steepness index m_P (T > T_g) = d log₁₀τ(T)/d( T_g/T). It is evidenced that m_P(T) = 1(T − T*), for T → T_g and T*= T_g − Δ T*. Basing on this finding, the new 3-parameter dependence for portraying the previtreous behavior of the primary relaxation time has been derived: τ(T) = C_Ω((T − T*)/T)^−Ω × [exp((T − T*)/T)]^Ω. The universality of obtained relations is evidenced for glass formers belonging to low molecular weight liquids, polymers (melt and solid), plastic crystals, liquid crystals, resins and relaxors. They exhibit clear preferences either for the VFT or for the critical-like descriptions, if recalled already used modeling. The novel relation can obey even above the dynamic crossover temperature, with the power exponent Ω ranging between ~17 (liquid crystals) to ~57 (glycerol), what may indicate the impact of symmetry on the previtreous effect. Finally, the emerging similarity to the behavior in the isotropic phase of nematic liquid crystals is recalled.