FLUOROPHOBIC EFFECT GENERATES A SYSTEMATIC-APPROACH TO THE SYNTHESIS OF THE SIMPLEST CLASS OF RODLIKE LIQUID-CRYSTALS CONTAINING A SINGLE BENZENE UNIT

4-Substituted 5,5,6,6,7,7,8,8,9,9,10,10,10-tridecafluorodecan-1- yloxy benzences, 1,11,12,12-heptadecafluorododecan-1-yloxybenzenes, and 2-me thyl-4-substituted 11,12,12,12-heptadecafluorododecan-1-yloxybenzenes benzenes were synthesized and characterized by a combination of techni ques consisting of differential scanning calorimetry (DSC), thermal op tical polarized microscopy, and small- and wide-angle X-ray diffractio n. Thermotropic s(A) and s(C) LC phases are exhibited by compounds wit h NO2, CN, CO2CH3, CH2OH, CO2H, and COCH3 substituents in the 4-positi on of the benzene ring. The thermal stability of the LC phase of these compounds increases with the increase of the length of the perfluorin ated segment of their alkoxy group. A ratio of the perhydrogenated [(C H2)(m)]/perfluorinated [F(CF2)(n)] segment lengths of m/n < 1 favors t he formation of LC phases when n + m = 10 and 12. Additional substitut ion in the 2-position of the benzene ring with a methyl group decrease s the thermal stability of the LC phase. The s(A) phase of these compo unds has a bilayered structure in which the perfluorinated segments ar e interdigitated. These compounds represent the simplest class of rodl ike liquid crystals containing a single benzene unit which exhibit cla ssic calamitic phases. The experiments reported in this paper demonstr ate a simple and convenient-method for the synthesis of liquid crystal s containing a single benzene unit via the fluorophobic effect.