Synthesis and mesogenic properties of a novel family of oligothiophene derivatives.

With the aim of developing new oligothiophene-based liquid crystals involving hydrogen bonding, new terthiophene derivatives containing an alkylamide group, N,N′-distearyl-2,2′ : 5′,2″-terthiophene-5,5″-dicarboxamide (DNC[sub 18]3T) and N,N′-dialkyl-5,5″-dibromo-2,2′ : 5′,2″-terthiophene-4,4″-dicarboxamides (DNC[sub n]DBr3T, n = 5, 8, 16, 18), were designed and synthesized, and their thermal behaviour examined. While DNC[sub 18]3T did not exhibit liquid crystallinity, DNC[sub n]DBr3T compounds with n = 8, 16, 18 were found to form smectic A phases. In addition to liquid crystal behaviour, crystal polymorphism was also observed for DNC[sub 16]DBr3T. It is shown that both the position of the amido group and the alkyl chain length greatly affect liquid crystal phase formation. The absence of liquid crystallinity in the corresponding ester derivatives suggests that intermolecular hydrogen bonding also plays a role in the formation of liquid crystal phases in the DNC[sub n]DBr3T system. [ABSTRACT FROM AUTHOR]