K. Czuprynski et al., Carborane-containing liquid crystals: a comparison of 4-octyloxy-4 '-(12-pentyl-1,12-dicarbadodecaboran-1-yl)biphenyl with its hydrocarbon analogues, LIQ CRYST, 26(2), 1999, pp. 261-269
4-Octyloxy-4'-(12-pentyl-1,12-dicarbadodecaboran-1-yl)biphenyl (1BC) has be
en synthesized along with three hydrocarbon analogues in which the 1,12-dic
arbadodecaborane is replaced by a phenyl (IPH), trans-cyclohexyl (1CH) or b
icycle [2.2.2]octyl (1BO) ring. The mesogenic properties of these materials
have been compared and contrasted in both their pure states and as binary
mixtures. The binary phase diagrams for the liquid crystal 1BC, with its hy
drocarbon analogues 1CH and 1BO exhibit excellent miscibility of the smecti
c A phase while the more highly ordered smectic phases (SmB and SmE) for th
e hydrocarbons are suppressed by 1BC. In contrast the binary mixture of 1BC
with the terphenyl analog (1PH) exhibits complex behaviour in which the th
ermal stability of the smectic E phase is enhanced. X-ray diffraction data
for the 1PH-1BC binary mixture suggest a strong in-plane molecular ordering
which might be attributed to intermolecular associations stabilizing the s
mectic E phase in preference to other smectic modifications.