2-(4-ALKYLPHENYL)-5-(ALKENYLOXY)PYRIMIDINES - SYNTHESIS, LIQUID-CRYSTAL TRANSITION-TEMPERATURES AND SOME PHYSICAL-PROPERTIES

We have recently reported the introduction of a carbon carbon double b ond into a wide variety of 5-n-alkyl-2-(4-n-alkoxyphenyl)pyrimidines t o produce the corresponding alkenyloxy derivatives. The position and n ature (E/Z) of the double bond were varied systematically and the effe ct on the liquid crystal transition temperatures studied. The position and nature (E/Z) of the double bond changed the conformation of the a lkenyloxy chain substantially. This resulted in higher smectic C and n ematic transition temperatures for compounds with a trans-double bond (E) at an even number of carbon atoms from the molecular core. Signifi cantly lower transition temperatures (including the melting point) wer e observed for materials with a cis-double bond (Z) at an odd number o f carbon atoms from the molecular core. We have now performed the same operation on the related 2-(4-n-alkylphenyl)-5-n-alkoxypyrimidines to produce the corresponding alkenyloxy derivatives. An interesting feat ure of the new results is the high melting points of the trans-substit uted materials and the low melting points of the terminally substitute d compounds. The smectic C transition temperatures of both series are high. No nematic phases could be observed. However, in admixture with other smectic C components, the new compounds lead to surprisingly fas t switching times, high smectic C transition temperatures and low melt ing points/crystallization temperatures in experimental mixtures desig ned for electro-optic display devices based on ferroelectric effects.