Liquid Crystals Derived from Semifluorinated Alkoxybenzoyl Hydrazines

Abstract

A variety of liquid crystals with semifluorinated tails including 4-alkoxybenzoic acids (1d–h), 4-alkoxybenzoyl hydrazines (2d–h), and N,N′-bis(4-alkoxybenzoyl) hydrazines (3d–m) have been synthesized, and their properties are compared with their perhydrogenated analogs. Semifluorination in compounds 1d–h suppressed nematic phases, and semifluorinated compounds 2d–h exhibit mesogenic behavior where none is found in their perhydrogenated counterparts. Compounds 3a–c with perhydrogenated chains display Cub and SmC phases. Introduction of one semifluorinated chain, 3d–h suppresses the Cub phase but induces a SmA phase, with lower melting but higher clearing temperatures compared to compounds with two semifluorinated chains, 3i–m. The mesogenic properties of some selected binary mixtures of these compounds 3a–d and some lateral fluoro substituted N,N′-bis (4-alkoxybenzoyl) hydrazines 7–9 are also discussed.

Keywords:

• binary mixtures
• lateral fluoro substitution
• nematic
• perhydrogenated chains
• semifluorinated mesogens
• smectic

Notes

Literature data in Table 1 were obtained from heating.

^a Compound exhibits several crystalline phases

^b Undetermined high-order smectic mesophase (e.g., SmB, SmE, SmH, SmK) [18]

^c Reported as Cr₁-Cr₂ phase transitions [52].

Data in Table 2 were obtained on heating.

^a Values from the second run. Compound exhibits two crystalline phases in the first DSC run but only one crystalline phase can be observed in the second run for the same sample.

Data in Table 3 were obtained from heating.

Data in Table 4 were obtained on heating.

Data in table 5 were obtained on heating.

^a Compound exhibits several crystalline phases. On cooling, 3b shows SmC phase at 150.4°C before becomes Cub phase at 146.5°C. On heating, the SmC phase could not be observed (phase sequence: Cr-Cub-I).

Data in Table 6 were obtained on heating.

^a Values from the first run. Compound exhibits three crystalline phases in the first DSC run but only two crystalline phases can be observed in the second run for the same sample.

^b Mesophase values observed using POM. Unit for enthalpy for compounds in Table 6 is J/g.

^a Compound exhibits several crystalline phases. Data in Table 7 were obtained on heating.

^a Compound exhibits several crystalline phases. Data in Table 8 were obtained on heating.