ABSTRACT. Novel homologous series: RO-C 6 H 4 -CH=CH-COO-CH 2 -C 6 H 4 -Br (p) synthesized and studied with a view to understand and establish the effects of molecular structure on liquid crystal (LC) behavior of a series. Series consists of eleven homologues. C 1 to C 7 members of a novel series are non-liquid crystals. Mesomorphism commences from Octyloxy (C 8 ) homologue and continued upto hexadecyloxy homologue (C 16 ) as enantiotropic nematic without exhibition of smectic property. The textures of a nematic phase are threaded or Schlieren. Transition temperatures (table-3) and textures are determined by an optical polarizing microscopy equipped with a heating stage. Cr-N/I and N-I transition curve behaved in normal manner in phase diagram, showing their phase behavior (figure-2). Odd-even effect is absent for N-I transition curve. Analytical and spectral data confirmed the molecular structures of a series. The LC properties are compared with the structurally similar series. The transition temperatures are relatively lower than the corresponding n-alkoxy benzoic acid. Thus, present novel series is partly nematogenic with absence of smectic property whose mesogenic phase length is low and of low ordered melting type. Thermal stability for nematic is 93.0°C and the mesophaselength ranges from 8 to 21°C.

Novel homologous series: RO-C6H4-CH=CH-COO-CH2-C6H4-Br (p) synthesized and studied with a view to understand and establish the effects of molecular structure on liquid crystal (LC) behavior of a series. Series consists of eleven homologues. C1 to C7 members of a novel series are non-liquid crystals. Mesomorphism commences from Octyloxy (C8) homologue and continued upto hexadecyloxy homologue (C16) as enantiotropic nematic without exhibition of smectic property. The textures of a nematic phase are threaded or Schlieren. Transition temperatures (table-2) and textures are determined by an optical polarizing microscopy equipped with a heating stage. Cr-N/I and N-I transition curve behaved in normal manner in phase diagram, showing their phase behavior (figure-1). Odd-even effect is absent for N-I transition curve. Analytical and spectral data confirmed the molecular structures of a series. The LC properties are compared with the structurally similar series. The transition temperatures are relatively lower than the corresponding n-alkoxy benzoic acid. Thus, present novel series is partly nematogenic with absence of smectic property whose mesogenic phase length is low and of low ordered melting type. Thermal stability for nematic is 93.0°C and the mesophaselength ranges from 8 to 21°C.

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