ORIENTATIONAL SUSCEPTIBILITY AND ELASTIC-CONSTANTS NEAR THE NEMATIC-ISOTROPIC PHASE-TRANSITION FOR TRIMERS WITH TERMINAL-LATERAL-LATERAL-TERMINAL CONNECTIONS

Magnetically induced Freedericksz measurements were performed in the n ematic liquid crystal phase to extract the elastic constants of a term inal-lateral-lateral-terminal trimer, i.e., a trimer in which the conn ections to the first and third mesogens are at the end of the mesogen and both attachments to the central mesogen are lateral. Polymeric liq uid crystals based on this unit have negative Poisson ratios. Addition ally, electric field Kerr measurements were performed in the isotropic phase to extract the orientational susceptibility. The elastic consta nts were found to be similar to values obtained for typical monomers, albeit with a slightly enhanced ratio K-33/K-11 and reduced ratio K-11 /K-22 especially near the transition temperature. The temperature depe ndence of the susceptibility was found to deviate significantly from t hat of typical monomers. The observed behavior is discussed in terms o f coupled order parameters representing the terminal and core mesogens of the molecule.