Bend and splay elastic constants and diamagnetic susceptibility anisotropies of four mesogenic cyclohexane carboxylates

Splay (K-11) and bend (K-33) elastic constants and magnetic susceptibility anisotropies have been determined for four mesogenic compounds with structu ral formulae Rl-C6H10-COO-C6H4-R2. Two of the compounds, namely, CPPCC (R1= C3H7,R2=CN) and CPBCC (R1=C4149, R2=CN) have terminal cyano groups, while t he others are BPPCC (R1=C3H7,R2=OC4H9) and PPPCC (R1=C5H7, R2=OC5H11). As e xpected, the magnetic susceptibility anisotropies are larger for the cyano compounds than those of the others. K-33/K-11 ratios are greater than one f or the cyano compounds and are less than one for the others. With the excep tion of PPPCC, this ratio decreases with increasing temperature. X-ray diff raction studies on the nematic phase of PPPCC show the presence of cybotact ic groups at lower temperature. The local smectic ordering of these groups increase the value of K-11 and thus reduce the value of K-33/K-11 at lower temperatures.