BEND AND SPLAY ELASTIC CONSTANTS AND DIAMAGNETIC SUSCEPTIBILITY ANISOTROPIES OF FOUR MESOGENIC CYCLOHEXANE CARBOXYLATES

Abstract

Splay (K11) and bend (K33) elastic constants and magnetic susceptibility anisotropies have been determined for four mesogenic compounds with structural formulae R1‒C6H10‒COO‒C6H4‒R2. Two of the compounds, namely, CPPCC (R1 = C3H7, R2 = CN) and CPBCC (R1 = C4H9, R2 = CN) have terminal cyano groups, while the others are BPPCC (R1 = C3H7, R2 = OC4H9) and PPPCC (R1 = C5H7, R2 = OC5H11). As expected, the magnetic susceptibility anisotropies are larger for the cyano compounds than those of the others. K33/K11 ratios are greater than one for the cyano compounds and are less than one for the others. With the exception of PPPCC, this ratio decreases with increasing temperature. X-ray diffraction studies on the nematic phase of PPPCC show the presence of cybotactic groups at lower temperature. The local smectic ordering of these groups increase the value of K11 and thus reduce the value of K33/K11 at lower temperatures.