On the smectic cybotactic groups and pretransition effects in the Miesowicz viscosity coefficient η₂

The Influence of Natural and Model Nanoinclusions on the Properties of Nematic Phase

“…Thus, after reaching the maximum the number Figure 2. The number of smectic cybotactic groups as a function of the reduced temperature, (TÀT NA )=T NA (T NA is the nematic-smectic A transition temperature), for 8OCB [21]. With decreasing of the reduced temperature the number is rising to reach the maximum and diminish afterwards.…”

“…are longitudinal and transverse correlation lengths and appropriate critical coefficients, respectively. The observed difference in the character of the temperature dependence of the cybotactic group volume, most probably results from the temperature behavior of the number of cybotactic groups [21]. The number can be estimated by dividing the cybotactic groups volume fraction, / cyb , by the single cybotactic group volume: u cyb = T À T NA =T NA ð Þ Àn jj À2n ?…”

“…Calculation of the cybotactic groups volume fraction using the Batchelor's formula is only some reasonable estimation, due to different reasons discussed in detail elsewhere [21].…”

“…u is the volume fraction of the cybotactic groups in the system. It can be argued that the nematic solvent viscosity coefficient at any given temperature T, can be estimated using the Arrhenius equation [21]:…”

“…The theory of the critical behavior of cybotactic nematic was given by Jähnig and Brochard [12]. Although these smectic cybotactic intrusions are not solid, but under favourable conditions could act like solid-like ones, which manifests in, e.g., twist and bend elastic constants K 22 and K 33 [13,14], rotational viscosity coefficient c 1 [13,15] and Miesowicz viscosity coefficient g 2 (directorn n is parallel to the flow viscosity v * ,n njj v * ) [13, [16][17][18][19][20][21]. This work concentrates on influence the inclusions have on the Miesowicz viscosity coefficient g 2 [16] in the liquid crystalline nematic phase.…”