Columnar Liquid Crystals from Star‐Shaped Conjugated Mesogens as Nano‐Reservoirs for Small Acceptors

Abstract

Shape‐persistent conjugated mesogens with oligothiophene arms of different lengths have been synthesized. Such mesogens possess free intrinsic space between their conjugated arms. They form columnar liquid‐crystalline phases, in which the void is filled by dense helical packing in the neat phase similar to an oligo(phenylene vinylene) derivative of equal size. The void can also be compensated by the inclusion of the small acceptor molecule 2,4,7‐trinitrofluorenone. In solution, the acceptor interacts with the core as the largest π‐surface, while in the solid material, it is incorporated between the arms and sandwiched by the star‐shaped neighbours along the columnar assemblies. The TNF acceptors are not nanosegregated from the star‐shaped donors, thus the liquid crystal structure converts to a nano‐reservoir for TNF (endo‐receptor). These host–guest arrangements are confirmed by comprehensive X‐ray scattering experiments and solid‐state NMR spectroscopy. This results in ordered columnar hexagonal phases at high temperatures, which change to helical columnar mesophases or to columnar soft crystals at room temperature.

Tailoring Chiral Discotic Liquid Crystals: Mesophase Engineering through Alternative Approaches and Chain Lengths

“…Cooling revealed reversible transitions at lower temperatures: 194.3 °C (Δ H =2.8 kJ/mol) and 87.2 °C (Δ H =6.9 kJ/mol), pointing to increased mesophase viscosity. These transitions were also evident in POM, where pseudo‐focal conic domains (Col h ) [21–23] changed appearance (Figure 5a), becoming more striated in the Col r phase (Figure 5b), possibly due to layer shrinkage along the columnar axis.…”

“…At the higher temperature of 81.7 °C (Figure S22c), the mesophase displayed smooth, pseudo-focal conic textures characteristic of the Col h phase. [21][22][23] As the temperature dropped further, the initially smooth textures transformed into band-like periodic patterns within the domains at 76.8 °C, signifying a clear phase transition to another phase (Col ob phase) while retaining pseudo-focal conic domains. [21][22][23] These textures undergo slight changes as temperature is lowered (corresponding to Col x phase), as shown in Figure S22a at À 10 °C.…”

“…[21][22][23] As the temperature dropped further, the initially smooth textures transformed into band-like periodic patterns within the domains at 76.8 °C, signifying a clear phase transition to another phase (Col ob phase) while retaining pseudo-focal conic domains. [21][22][23] These textures undergo slight changes as temperature is lowered (corresponding to Col x phase), as shown in Figure S22a at À 10 °C. DSC analysis indicated an additional transition at 4.1 °C, corroborated by XRD studies.…”

Enantiomers Self-Sort into Separate Counter-Twisted Ribbons of the Fddd Liquid Crystal─Antiferrochirality and Parachirality

“…Our preliminary studies also suggest that this phase and its variants may be widespread in polycatenars, including those formed by hydrogen-bonded half-rods and in side-chain LC polymers. It would also not be surprising if it was found in compounds with 3-arm star molecules of C 3 symmetry that also form a columnar phase at higher temperatures. , As the Fddd phase is becoming a major LC type, we engaged in a more systematic study of its features. Furthermore, we undertook to find if rodlike polycatenars with a strong chiral center could produce an ordered chiral LC phase of homochiral ribbons.…”

Paramagnetic supramolecular mesogens: A new paradigm in self-assembled magnetic materials

“…These endoreceptors are able to accept up to three guests. [33][34][35] The resulting supramolecular or covalently bonded supermesogens 36 selfassemble in highly ordered double or triple nanosegregated structures. 37,38 These results prompted us to design new supermesogens 1 and 2 (Fig.…”