Divergence rotational viscosity

If there is a phase transition from a nematic to a smectic phase, pretransitional effects are observed in the neighbourhood of the transition [9, 44, 49-51]. Figure 10 [9] shows this behaviour for 4-/7-octyloxy-4 -cyanobiphenyl (80CBP) with a nematic-smectic phase transition at 340.3 K. Pretransitional effects cause a divergence of the shear viscosity coefficient 772 and the rotational viscosity /j. 

A divergence of the rotational viscosity is observed in the neighbourhood of transitions to smectic phases as the molecular rotation will be hindered by the pretransition-al formation of the smectic layer structure. Figure 10 shows this effect for 80CBP [9]. The divergence can be described by an equation similar to Eq. (35) [52-54] ... 

A main problem in evaluating the divergence of the rotational viscosity in the vicinity of a smectic phase is the separation of the non-divergent part. An additional determination of the pressure dependence can be very advantageous. First, the pressure dependence can be studied directly, as the pressure dependence of the non-divergent part is less pronounced than its temperature dependence. Secondly, the above discussed... 

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