Azomethine Schiffs Base Mesogens

These two ring azomethines gave chiral nematic phases which had relatively low thermal stabilities, but comparatively short phase ranges as demonstrated by compounds 28 and 29. 

The introduction of a third ring to give materials such as compound 30, led to markedly higher thermal stabilities. This compound is reported as having an optical rotation of 25 000 degrees mm in its chiral nematic phase, further highlighting the extraordinary optical properties associated with the chiral nematic mesophase. 

However, despite showing promising thermal stability, this type of mesogen fell from widespread use simply because the azomethine linkage (-CH = N-) imparts colour to the material and proved too sus- 

This class of chiral nematic materials clearly demonstrated their potential, as they 

The ability of the chiral 2-methylbutyl moiety to generate very short pitch chiral nematic phases was by now widely recognised. It was not therefore surprising that a number of research groups should attempt 

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