Mechanical Measurements on Free-Standing Films of Smectic Liquid-Crystal Phases

Abstract

Shear mechanical properties have been measured for free-standing films of the liquid crystal $n$-hexyl 4′-$n$-pentyloxybiphenyl-4-carboxylate (65OBC) in its stacked-hexatic $B$ phase. The smectic-$I$ phases of (±)-4-(2′-methylbutyl)phenyl 4′-$n$-nonyloxybiphenyl-4-carboxylate and (-1)-2 methylbutyl 4-(4′-$n$-decyloxybenzylideneamino) cinnamate (DOBAMBC) were also studied. Unlike the crystal $B$ phase, none of these phases exhibited an in-plane shear modulus. Enhanced crystalline surface ordering was observed in 65OBC.