Orientational long-range

Similar to cholesteric liquid crystals, the nematics have an orientational long-range order with the deviation that the direetion of the preferred orientation does not rotate (Fig. 2a). If, however, a chiral mesogen is dissolved in a nematic liquid crystal, the latter will be transformed into a eholesterie liquid crystal. 

From these experiments we can conclude that the length of the flexible spacer has no measurable influence on the orientational long range order of the mesogenic side chains. If on the contrary l-l.c. s are attached to the polymer backbone, the state of order is reduced. 

The cholesteric mesophase is a helically disturbed nematic phase. As in the nematic phase, the centers of gravity of the mesogenic molecules are statistically disordered, whereas the long molecular axes possess an orientational long range order with respect to the director. The director, however, is not constant in space, but continuously... 

As the cholesteric phase is a twisted nematic phase, the orientational long range order of the mesogenic molecules, characterized by Eq. (3) ... 

Liquid crystal is a term that is now commonly used to describe materials that exhibit partially ordered fluid phases that are intermediate between the three dimensionally ordered crystalline state and the disordered or isotropic fluid state. Phases with positional and/or orientational long-range order in one or two dimensions are termed mesophases. As a consequence of the molecular order, liquid crystal phases are anisotropic, i.e., their properties are a function of direction. 

Orientational long-range order, positional short-range order... 

In conventional LC phases the motion of the molecule is restricted only by the anisotropic interactions with its neighbors. This leads to the formation of the orientational long range order and in the case of smectic phases, to an additional lamellar sti ucture. However, completely different conditions normally exist in a liquid crystalline polymer. 

The angle 6 implied by these parameter values at strain is about 8.5°. The actual crystal can assume only those angles characteristic of (lOn) orientations, where n = 5,9,13,..., for this reconstruction, and 8.5° is about midway between the (105) and (109) orientations. Long range elastic effects, which have not been taken into account in the discussion in this section, would tend to drive the angle toward the larger angle orientation. 

Liquid crystals in which the molecules have an orientational long range order and also some type of laminar order. There are several types of smectic phases which correspond to various kinds of ordering. 

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