A Chalconyl homologous series: RO-C6H4-CH=CH-CO-C6H4-OC14H29(n) (meta) is synthesized and studied with a view to understand and establish the effect of molecular structure on Liquid crystal behaviour by reducing molecular rigidity through diminishing of a phenyl ring and a central carboxy or vinyl carboxy group from a molecule. Novel series consists of thirteen homologues (C1 to C18). First member (C1) homologue is nonliquid crystal and the rest of the homologues (C2 to C18) are enantiotropically ( C2 to C5) nematogenic or monotropically (C6 to C18) nematogenic plus smectogenic of low mesophaselengths and low transition temperatures ( 38°C to 76°C). Transition temperatures were determined by an optical polarizing microscopy (POM) equipped with a heating stage. Cr-N/I, N-I, I-N, N-Sm transition curves behaved in normal manner in a phase diagram. N-I and I-Sm transition curves exhibited odd-even effect. Textures of nematic phase are threaded or schlieren and that of the smectic phase are of the type A or C. Analytical, spectral and thermal data supported molecular structure of homologues. Thermal stability ( N-I/ I-N) of series for nematic is 67.5°C and that of the smectic is very low. Group efficiency order derived on the basis of thermal stability is as under. –Cl with –C6H4.COO- > -OC14H29(n) without –C6H4.COO-with reference to central bridge –CH=CH-CO-.
International Letters of Chemistry, Physics and Astronomy (Volume 64)
V. S. Sharma et al., "Study of the Effects of Decreasing Molecular Rigidity on Mesomorphism", International Letters of Chemistry, Physics and Astronomy, Vol. 64, pp. 69-76, 2016