Splay elasticity in an oligomeric liquid crystal

Abstract

A magnetically-induced Freedericksz transition was used in conjunction with capacitance techniques to determine the splay elastic constant of the 4,4′-dialkoxyphenylbenzoate monomer ‘5OO5rsquo; [C₅H₁₁OC₆H₄COOC₆H₄OC₅H₁₁] and its dimer. As a function of reduced temperature in the nematic phase, it was found that K ₁₁ of the dimer is only about 20 per cent larger than that of the monomer. Moreover, the values of K ₁₁/S ² versus reduced temperature, where S is the scalar order parameter, are equal to within experimental noise. These results suggest that for short oligomers Meyer's entropic model for splay elasticity in polymer liquid crystals is not applicable. A lowest order correction to the entropic model is suggested, which partially accounts for excluded volume and dispersive effects.