Achiral flexible liquid crystal trimers exhibiting chiral conglomerates

Synthesis and Properties of Maleic Acid Cholesteryl Monoester–Citric Acid Triester

A new maleic acid cholesteryl monoester–citric acid trimester (MACM-CAT) containing three cholesterol units has been synthesised successfully. The structure was characterised by a series of spectroscopic methods and thermal analysis including polarising optical microscopy. The results showed that MACM-CAT displayed a triangular-like ordered layered structure and exhibited a good liquid crystalline behaviour. The introduction of sodium citrate onto cholesterol units is favourable for the formation of hydrogen bonds of MACM-CAT and improvement of the stability. More importantly, the study provides a novel route for the synthesis of liquid crystalline materials.

Linear symmetric liquid crystal trimers exhibiting supramolecular chiral architectures

We prepared a homologous series of achiral liquid crystal trimers (I-n) in which two phenylpyrimidine units and one biphenyl unit were connected via flexible spacers, and investigated the physical properties. All the trimers possessing odd-numbered methylene spacers exhibited soft crystalline chiral conglomerate phases. X-ray diffraction measurements reveal that they have an intercalated layer structure. On the other hand, the trimers possessing even-numbered spacers showed nematic and smectic C phases. We investigated the surface structures of odd-membered trimers in the soft crystalline phases using scanning electron microscopy. Trimers I-3 and I-5 were found to form cylindrical tubes, whereas trimers I-7, I-9 and I-11 toroidal pits. We discuss the formation of diverse supramolecular architectures in terms of the anisotropy of the chirality transfer.

Porous surface of an achiral trimer in the chiral conglomerate phase catalyzes a direct aldol reaction

The honeycomb-like porous surface consisting of linear trimer molecules catalyzes the direct aldol reaction of acetone with benzaldehyde at room temperature to give racemic β-hydroxyketone.

Achiral flexible liquid crystal trimers exhibiting gyroid-like surfaces in chiral conglomerate phases

Chiral conglomerate phases have attracted much attention not only for the spontaneous mirror symmetry breaking but also for their nanostructures. We investigated both surface and bulk structures of a homologues series of an achiral liquid crystal trimer I-(n,m) exhibiting soft crystalline chiral conglomerate phases by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The trimers were found to form bicontinuous networks. In particular, trimer I-(9,9) exhibited a single gyroid-like surface accompanying periodic distribution of dimples with a size of about 100 nm. It showed a sponge-like structure in the bulk of the material. The twist conformation of the flexible trimer I-(n,m) can cause layer deformation, which produces bicontinuous networks exhibiting optical activity.

The dependency of twist-bend nematic liquid crystals on molecular structure: a progression from dimers to trimers, oligomers and polymers

This article gives an overview on recent developments concerning the twist-bend nematic phase. The twist-bend nematic phase has been discussed as the missing link between the uniaxial nematic mesophase (N) and the helical chiral nematic phase (N*). After an introduction discussing the key physical properties of the N_TB phase and the methods used to identify the twist-bend nematic mesophase this review focuses on structure property relationships and molecular features that govern the incidence of this phase.

Synchronization of conformational chirality in mixtures of achiral bent-core molecules

SEM images and frequency variation of ε′′ in PDMBC with flat layers, M50 and M20 with respectively weak and strong layer deformation.