English abstract
The present study is concerned with synthesizing and studying the
mesomorphic properties and the thermal behavior of four novel fluorinated
chiral (bifurcated tail) organo-siloxane liquid crystals using established
procedures and protocols. The four liquid crystal mesogens (7a, 7b, 7c & 7d)
have a chiral head made up of seven carbon that has (R) absolute
configuration but with different length of the carbon chain tail (C-11, C-10, C8 & C-7) respectively. The general name of this series is (R)-4'-(heptan-2-
yloxy)-3'-nitro-[1,1'-biphenyl]-4-yl-2-fluoro-4-((n-(1, 1, 1, 3, 5, 5, 5-
heptamethyltrisiloxanyl)alkenyl)oxy)benzoate, where n= 11, 10, 8, 7 for 7a,
7b, 7c & 7d, respectively. The yield for the four synthesized LCs was: 32.7%,
38.5%, 41.5% and 48.1% for 7a, 7b, 7c & 7d, respectively.
The structures of all synthesized final products and intermediates were
confirmed using 1H-NMR, 13C-NMR spectroscopy and LC-MS (where
possible). Phase transition behavior of this series was studied using
polarized optical microscopy (POM). All the products were found to be
ferroelectric. Two liquid crystals in this study (C-7 and C-8 LC (7c & 7d) )
exhibited a smectic C* deVries behavior while exhibiting a new higherordered hexagonal smectic F* phase (SmF*) which was observed upon
cooling. The other two mesogens (7a & 7b) exhibited SmC* at room
temperature with a relatively narrow transition window.
