Mesomorphic behaviour of some 4-n-Pentanoyl-4′-n-alkanoyloxy azobenzenes (PPAPE). A new series of liquid-crystal compounds

In this paper we present the synthesis and the study of the homologous series $$CH_3 - (CH_2 )_m - CO - C_6 H_4 - N = N - C_6 H_4 - O - CO - (CH_2 )_n - CH_3$$ whithm=3 andn ranging from zero to sixteen. Transition temperatures, enthalpies and entropies have been determined making use of optical methods, differential scanning calorimetry and X-ray diffraction. Smectic and/or nematic phases have been observed for all the homologues with a complex polymorphism in some cases. A comparison with the seriesm=0,m=1 andm=2, precedently studied, is also reported.