Smectic dynamic scattering

It is energetically unfavorable to alter the layer thickness of the smectic phase, therefore any process that relies on this feature is very unlikely to occur. However, bending of the smectic layers is possible, because this need not cause a change in the layer thickness thus the molecules can undergo a splay (A, ) distortion. In a smectic film, any point distortion of the layer, e.g., arising from a surface feature, propagates for some distance into the film this feature is important for electrically addressed dynamic scattering devices. Bend ( 33) and twist ( "22) elastic constants approach infinity at the nematic (N) to smectic transition. 

The conductivity of the smectic phase is important rather than rely on impurities in the liquid crystal or degradation products of the dynamic scattering, it is desirable specifically to add ionic dopants. In the early work, the homeotropic aligning dopant [hexadecyltrimethyl ammonium bromide (HMAB)] conveniently also acted as the... 

The conductivity of the SmA phase is also dependent on the texture or molecular arrangement of the smectic phase. The scattering state (asc) has a different conductivity to the homeotropic state (Ctr) it was found that when cTsc is larger than oVr, then dynamic scattering will occur [57] and that, as the ratio cTsc/cTtr increases, the threshold voltage decreases. 

In smectic C materials, the relative twist of the planes is uncoupled to the layer thickness, giving rise to strong, nematic-like scattering [106]. There are relatively few light scattering studies of either achiral or chiral SmC phases, despite the technological importance of the ferroelectric SmC phase. This is in part due to the few discussions of the elastic theories of these phases, and in particular descriptions that include dynamic behaviour. Indeed it is only relatively recently that Leslie et al. [107] de-... 

K. C. Chu, W. L. McMillan, Static and dynamic behavior near the second order Smectic-A-Neraatic phase transition by light scattering, Phys. Rev. A 1975,11, 1059-1067. 

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