Chirality-Induced Liquid Crystalline Properties of Seven-Ring Trimeric Mesogens Incorporating Dual Chiral Centers

Laterally Brominated Symmetric Liquid Crystal Trimers with (S)-(-)-2-Methylbutyl-4′-(4″-phenyl)benzoate Exhibiting N* and Blue Phases

“…One such example is shown in a series of non-symmetric dimers which incorporates a cholesteryl moiety [13]. Due to the similarities in transitional properties between dimers and trimers, the pronounced difference in DS N Ã I =R magnitude between the even and odd trimers can, therefore, be reasonably justified based FIGURE 2 The dependence of chiral nematic-isotropic transitional entropy, DS N Ã I =R on the number of methylene units, n in the flexible spacers for compounds 4b-4f and 4h, and compounds 5a-5c and 5e-5h (dotted line) as previously reported [7]. on the understanding on the dimeric models.…”

“…For compounds 4a-4h, the larger size of Br atom (atomic radius, 94 pm) as compared to H atom (53 pm) reduces the shape anisotropy of compounds 4a-4h to an extent that the resulting effect is observed in the thermal properties of these compounds. In addition, the odd spacers in compounds 4a, 4c, 4e, and 4g cause the shape anisotropy of these compounds to decline further leading to FIGURE 6 The comparison between N Ã -I transition temperatures of compounds 4b-4f, 4h, and those of the previously reported laterally unsubstituted analogous trimers [7]. the significantly lower chiral nematic-isotropic transition temperatures (Fig.…”

“…In order to study the influence of the presence of lateral bromine atoms on the liquid crystalline properties, comparison is made between the properties of compounds 4a-4h and those of our earlier reported analogous trimers [7]. The trimers, with spacers ranging from pentyl to dodecyl, are labeled as 5a-5h and the general molecular structure of the trimers is shown below.…”

“…For instance, the trimer with two C 6 H 12 spacers possesses clearing temperature of 266.0 C [7]. Such thermal properties of the trimers are mainly attributed to the long calamitic molecular structure and the presence of seven aromatic rings which favours strong intermolecular attraction.…”

Effects of combining of different flexible spacers in liquid crystal trimers and tetramers on transition properties

“…These molecules exhibit a remarkable odd-even effect in their transition properties, which depends on the length and parity of the flexible spacer. The structure property relationships in LC trimers and tetramers have been studied by a number of researchers [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], and we have also studied odd-even effects in LC trimers (1) [21] and tetramers (2) [22]. The molecules (1) and (2) contain two kinds of flexible spacers, namely O(CH 2 ) m O and COO(CH 2 ) n O groups.…”