화학공학소재연구정보센터
Molecular Crystals and Liquid Crystals, Vol.624, No.1, 51-58, 2016
Mesomorphism dependence on lateral substitution of functional groups and their position in series: 4(4(')-n-alkoxy benzoyloxy)-3-chloro phenyl azo-2('')-methoxy benzenes
Eleven homologues of the title series were synthesized. The methyl-to-pentyl derivatives are nonmesomorphic. The nematic mesophase commences from the sixth member of the series without any smectic phase. An odd-even effect in the nematic-isotropic transition curve is not observed. The nematic mesophase appeared as a threaded or a Schlieren-type texture as observed through a hot-stage polarizing microscope. The nematic-isotropic transition temperatures are between 89 degrees C and 127 degrees C with the mesomorphic range varying from 9 degrees C to 44 degrees C at the hexyl and tetradecyl derivative of the series, respectively. The nematic-isotropic transition curve initially rises and then falls in a normal manner as the series is ascended, but it abnormally rises beyond the 10th homologue. The series is enantiotropic nematic with a middle-ordered melting type. Analytical data support the structures of the molecules. The thermal stability and some other mesomorphic characteristics are compared with structurally similar homologous series. The average nematic-isotropic thermal stability is 105.4 degrees C.