Inducing Liquid Crystallinity in Dilute MXene Dispersions for Facile Processing of Multifunctional Fibers

The liquid crystal (LC) phases of two-dimensional (2D) transition metal carbides/nitrides (MXenes) has enabled the production of their unique macro-architectures with ordered microstructure and enhanced properties. However, LC phases in...

Tuning the Liquid Crystallinity of Cholesteryl-o-Carborane Dyads: Synthesis, Structure, Photoluminescence, and Mesomorphic Properties

A set of mesomorphic materials in which the o-carborane cluster is covalently bonded to a cholesteryl benzoate moiety (mesogen group) through a suitably designed linker is described. The olefin cross-metathesis between appropriately functionalized styrenyl-o-carborane derivatives and a terminal alkenyl cholesteryl benzoate mesogen (all type I terminal olefins) leads to the desired trans-regioisomer, which is the best-suited configuration to obtain mesomorphic properties in the final materials. The introduction of different substituents (R = H (M2), Me (M3), or Ph (M4)) to one of the carbon atoms of the o-carborane cluster (Ccluster) enables the tailoring of liquid crystalline properties. Compounds M2 and M3 show the chiral nematic (N*) phase, whereas M4 do not show liquid crystal behavior. Weaker intermolecular interactions in the solid M3 with respect to those in M2 may allow the liquid crystallinity in M3 to be expressed as enantiotropic behavior, whereas breaking the stronger intermolecular interaction in the solid state of M2 leads directly to the isotropic state, resulting in monotropic behavior. Remarkably, M3 also displays the blue phase, which was observed neither in the chiral nematic precursor nor in the styrenyl-cholesterol model (M5) without an o-carborane cluster, which suggests that the presence of the cluster plays a role in stabilizing this highly twisted chiral phase. In the carborane-containing mesogens (M2 and M3), the o-carborane cluster can be incorporated without destroying the helical organization of the mesophase.

Tailored growth of graphene oxide liquid crystals with controlled polymer crystallization in GO-polymer composites

Kinetics of polymer crystallization determines the liquid crystallinity of graphene oxide and its long range alignment.

The effect of liquid crystalline graphene oxide compared with non-liquid crystalline graphene oxide on the rheological properties of polyacrylonitrile solution

In this article, polyacrylonitrile (PAN) and two kinds of graphene oxide (GO) with different structural properties are blended in dimethyl sulfoxide (DMSO) according to a certain ratio to prepare stable-spinning solution. One kind of GO is purchased, and we call it GO1. The other is a kind of self-made GO with liquid crystal property in solution, which is called GO2. The effects of two kinds of GO on the rheological properties of PAN/GO spinning solution (15 wt%) were studied. The results show that the viscous activation energy of the liquid crystal GO2/PAN blend solution is significantly higher than that of the nonliquid crystal GO1/PAN blend solution. Moreover, the liquid crystal system is more obviously affected by temperature. The structural viscosity index of the liquid crystalline GO2/PAN solution is obviously lower than that of the GO1/PAN solution. It indicates that the existence of liquid crystallinity is beneficial to the spinning of the solution. In the low-frequency region, the addition of GO1 makes the solution more elastic, and the addition of GO2 makes the solution more viscous.

Conclusion—from soft matter to life

The Conclusion looks at the topics that haven't been covered in this VSI. There is so much more to the topic to be learnt: recent developments in rheology at the single molecule level through atomic force microscopy, and the single polymer imaging of confocal microscopy to name but a few. It is an undisputed truth that, through evolution, life itself has recruited the structures of soft matter for its own purposes. Polymers, membranes, liquid crystallinity, self-assembly form its fundamental constituents, from the humblest bacterium to the most complex multicellular creature. The tree of life has taken these materials and combined them in vast complexities of such intricacy that the student of simple systems is easily bewildered by the questions of life.

Synthesis of multifunctional liquid crystalline epoxy resin embedded cyclic-siloxane chain with Tg-less behavior and enhanced toughness

A novel tetrafunctional mesogenic epoxy monomer with a cyclic-siloxane chain as a central part was successfully synthesized and characterized by proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, differential scanning calorimetry, and polarized optical microscopy. The transition temperature and liquid crystallinity of cyclic-siloxane type mesogenic epoxy were compared with those of linear-siloxane type mesogenic epoxy. Moreover, epoxy thermosets were prepared based on the cyclic- and linear-siloxane type mesogenic epoxy monomers and 4,4′-diaminodiphenylethane. The effects of epoxy backbone moiety on thermal and mechanical properties were investigated in detail. As a result, the cyclic-siloxane type mesogenic epoxy thermoset shows glass transition temperature-less behavior and low coefficient of linear thermal expansion without a decrease in toughness.

Induction of Polyacetylene to a Chiral Smectic Liquid Crystal–Chiral Direct Conversion

The synthesis of polyacetylene-bearing pyrimidine-type three-ringed mesogenic core exhibiting smectic C (SmC) characteristics was conducted. Gas-phase iodine doping of the polymer provided evidence of chemical interaction between the polyene and iodine, which acted as an electron acceptor. The side-chain fluorine atom tilted the mesogen moiety to form SmC as a tilted liquid crystal. The addition of a small amount of chiral inducer yielded SmC* of the polymer as the chiral version of SmC. The liquid crystallinity and electronic properties of the π-conjugated chiral liquid crystal polymer with a helical structure were evaluated.