Phase transition behaviour of novel Y‐shaped liquid crystal oligomers

Abstract

We have designed novel liquid crystal oligomers in which three mesogenic units are connected via 3,5-dihydroxybenzoic acid. 4-Cyanobiphenyl-49-yl 3,5-bis{6-[4-(5-octylpyrimidin-2-yl)phenyloxy]hexyloxy}benzoate and 4-(5-octylpyrimidine-2-yl)phenyl 3,5-bis{6-[4-(5-octylpyrimidine-2-yl)phenyloxy]hexyloxy}benzoate have been prepared, and their physical properties investigated by optical microscopy and differential scanning calorimetry. The Yshaped liquid crystal oligomers were found to show a direct phase transition from isotropic liquid to anticlinic SmC (SmCanti) phase.

Non-Symmetric Liquid Crystal Dimers: High Thermal Stability in Nematic Phase Enhanced by Thiophene-2-Carboxylate Moiety

“…At high-field, the twelve methylene protons of the C 8 H 16 spacer give rise to two sets of multiplets at d=1.44-1.88 ppm. A triplet at d=4.07 ppm assignable to four methoxy protons, on the other hand, is similar to the absorption reported for 5-octylpyrimidine-2-yl oligomers [17]. Although the overall structure is non-symmetric due to two different mesogenic groups, the appearance of only one triplet owing to the two pairs of methoxy protons indicates the presence of symmetry in the flexible spacer.…”

λ-Shaped azomesogens with polar chloro- and nitro-substituents

“…Recently Yoshizawa et al [15] have reported the synthesis and physical properties of novel S-shaped LC oligomers in which two U-shaped mesogenic molecules are connected. Yoshizawa et al [16] have also reported novel Y-shaped LC oligomers in which three mesogenic units are connected by 3,5-dihydroxybenzoic acid. Y-shaped LC oligomers are found to exhibit only an anticlinic SmC anti (SmC) phase.…”

Synthesis and Phase Transition Behavior of Novel Liquid Crystal Tetramers

“…We have reported liquid crystal oligomers in which cyanobiphenyl and phenylpyrimidine moieties are connected via a flexible spacer [18][19][20], 1,3-dihydroxybenzene [21], 3,4-dihydroxybenzoic acid [22][23][24] or 3,5-dihydroxybenzoic acid [25], as shown in Figure 1. Intermolecular interactions between such mesogenic moieties were found to have significant effects on the molecular assemblies in the liquid-crystalline phases: (i) antiparallel interactions between cyanobiphenyl moieties promote the formation of N and SmA phases, (ii) interactions between phenylpyrimidine moieties were found to stabilize smectic phase [26], and (iii) interactions between cyanobiphenyl and phenylpyrimidine moieties are known to induce an SmA phase [27].…”