Abstract
Tristriazolotriazines (TTTs) with a threefold alkoxyphenyl substitution were prepared and studied by DSC, polarized optical microscopy (POM) and X-ray scattering. Six pentyloxy chains are sufficient to induce liquid-crystalline behavior in these star-shaped compounds. Thermotropic properties of TTTs with varying substitution patterns and a periphery of linear chains of different lengths, branching in the chain and swallow-tails, are compared. Generally, these disks display broad and stable thermotropic mesophases, with the tangential TTT being superior to the radial isomer. The structure–property relationships of the number of alkyl chains, their position, length and structure were studied.
Highlights
Despite earlier accounts [1,2], t-TTTs 1 are sensitive to high temperatures
The cyclocondensation of chlorotriazoles 7 is the direct route to the isomeric r-TTTs 2 [58,59]
Most r-TTTs known today were obtained by thermal isomerization of the tangential isomer
Summary
Tristriazolotriazines (TTTs), with a threefold alkoxyphenyl substitution [1,2,3,4] (Figure 1), belong to the youngest classes of discotic liquid crystals (DLCs) [5,6,7,8,9,10,11,12,13,14,15,16] and to the small subgroup of DLCs with a heterocyclic [17,18,19,20,21,22,23,24,25,26] and electron-deficient core [27,28,29,30,31,32,33,34,35,36]. Two C3 -symmetrical isomeric forms of these star-shaped molecules are known: the paddle-wheel with phenyl substituents in tangential positions (t-TTT) 1, and, if the aromatic rings are attached to the radial positions, the propeller (r-TTT) 2 (Figure 1). This ostensible small change from tangential to radial substitution severely alters the mesomorphic properties. The objective of this report is to elucidate the correlation between the mesomorphism of TTTs and the composition of their periphery This includes the number of side chains, the variation of their position, their length and branching
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