Synthesis, mesomorphic and geometrical approaches of new non-symmetrical system based on central naphthalene moiety

Abstract

ABSTRACT New non-symmetrical homologues series based on central naphthalene moiety, (E)-4-(4-(hexyloxy phenyl diazenylnaphthalene-1-yl-4ʹ-alkoxybenzoate (I 6/n), were synthesised and their mesomorphic properties was investigated. The prepared group constitutes four homologues bearing two terminal alkoxy chains of different proportionation. Elemental analyses, FT-IR and NMR spectroscopy were carried out to elucidate their molecular structures. Examination of their mesomorphic properties, were conducted via differential scanning calorimetry (DSC) and polarised optical microscopy (POM). DSC and POM investigations indicated that all the synthesised homologues are monomorphic possessing the enantiotropic nematic (N) phase. A comparative study was conducted between the present investigated central naphthalene series (I 6/n) and their corresponding central benzene analogues (II 6/n). The results indicated that, the mesophase type and stability as well as the mesophase temperature are affected by the protrusion of the naphthalene group. Theoretical calculations are in accordance with the experimental values of the investigated series. Moreover, the location of naphthalene group in the centre of the molecular geometry, increases the rigidity of the molecule, thus affects their thermal and physical parameters. The experimentally determined nematic stability was correlated with the calculated parameters and the study reveals that there are many factors sharing together to different extents in the enhancement of the behaviour of the observed nematic phase, depending on the different proportionation of the terminal lengths.