Institute of Physics, University of Silesia, Katowice, Poland.
J Phys Condens Matter. 2013 Jun 19;25(24):245105. doi: 10.1088/0953-8984/25/24/245105. Epub 2013 May 29.
Results of studies of the static and dynamic dielectric properties in rod-like 4-n-octyloxy-4'-cyanobiphenyl (8OCB) with isotropic (I)-nematic (N)-smectic A (SmA)-crystal (Cr) mesomorphism, combined with measurements of the low-frequency nonlinear dielectric effect and heat capacity are presented. The analysis is supported by the derivative-based and distortion-sensitive transformation of experimental data. Evidence for the I-N and N-SmA pretransitional anomalies, indicating the influence of tricritical behavior, is shown. It has also been found that neither the N phase nor the SmA phase are uniform and hallmarks of fluid-fluid crossovers can be detected. The dynamics, tested via the evolution of the primary relaxation time, is clearly non-Arrhenius and described via τ(T) = τ(c)(T-T(C))(-φ). In the immediate vicinity of the I-N transition a novel anomaly has been found: Δτ is proportional to 1/(T - T*), where T* is the temperature of the virtual continuous transition and Δτ is the excess over the 'background behavior'. Experimental results are confronted with the comprehensive Landau-de Gennes theory based modeling.
呈现了各向同性（I）-向列（N）-近晶 A（SmA）-晶体（Cr）型混合态的 4-正辛氧基-4′-氰基联苯（8OCB）的静态和动态介电性能的研究结果，这些结果与低频非线性介电效应和热容的测量相结合。通过基于导数的和对实验数据的失真敏感的变换来支持分析。证明了 I-N 和 N-SmA 预过渡异常，表明了三叉点行为的影响。还发现，无论是 N 相还是 SmA 相都不是均匀的，可以检测到流体-流体交叉的标志。通过主要弛豫时间的演变测试的动力学显然是非 Arrhenius 的，并通过 τ(T) = τ(c)(T-T(C))(-φ)来描述。在 I-N 转变的附近，发现了一个新的异常：Δτ与 1/(T - T*)成正比，其中 T*是虚拟连续转变的温度，Δτ是超过“背景行为”的过剩值。实验结果与基于综合朗道-德·热内斯理论的建模进行了对比。
