Mesomorphism Dependence on Cis-Trans Configuration and Varying Terminal/Lateral Group

A chalconyl trans vinyl ester homologous series of thermotropic liquid crystals RO-C₆H₄-CH=CH-COO-C₆H₄-CH=CH-CO-C₆H₃ (OCH₃)₂ meta-para is synthesized and studied with a view to understand and establish the relation between molecular structure and mesomorphism or mesomorphic behaviors. Novel homologous series consists of thirteen homologues (C₁ to C₁₈). First five (C₁ to C₅) homologues are nonmesogenic. Rest of the homologues (C₆ to C₁₈) homologues is mesogenic. Monotropically smectogenic character appears from C₆ to C₁₀ homologue and C₁₂ to C₁₈ homologues are enantiotropically smectogenic. Nematogenic property is totally absent throughout a series. Textures of smectic phase are of the type smectic A or C. Transition curves of a phase diagram behaved in normal manner. Analytical, spectral and thermal data supports the molecular structures of homologues. Odd-even effect is observed for Sm-I/I-Sm transition curve. Thermal stability for smectic is 93.7 °C and the mesomorphic phase lengths from enantiotropic homologues for smectic from minimum to maximum is 6.0 °C to 28.0 °C at the C₁₂ and C₁₈ homologue respectively. Series is smectogenic without exhibition of nematic property. The group efficiency order on the basis of thermal stability is derived; from comparative study of present series and analogous series.