Liquid Crystal Formation Research Articles

A Clinical Anti-Ageing Comparative Study of 0.3 and 0.5% Retinol Serums: A Clinically Controlled Trial

Background: Retinol influences the process of keratinization of the epidermis, which improves stratum corneum structure and reduces transepidermal water loss. It also significantly enhances mature skin by brightening hyperpigmentation and reducing the signs of photoageing. Cosmeceuticals are intended to both provide aesthetic effects for the skin and allow dermatological treatment. The aim of the study was to assess the rejuvenating effect of retinol serum on facial skin at concentrations of 0.3 and 0.5%, as well as any improvements in skin brightening and elasticity. Materials and Methods: Thirty-seven volunteers were included in the study, after confirming tolerance. The novel formula was applied once daily to the face for a period of 12 weeks: one retinol concentration on the left side and the other on the right. The initial study with liquid crystal formula (study vehicle) was carried out for 8 weeks on 28 volunteers. Treatment efficiency was evaluated at baseline, and 56 and 84 days following treatment using the multi probe adapter and Fotomedicus imaging system. PRIMOS was used to measure skin surface roughness. The visual analogue scale method enabled the results to be determined by 3 independent specialists. Results: Skin hyperpigmentation, unevenness, and wrinkles gradually decreased over the course of treatment, both on the left and right parts of the face. Adverse events were predominantly mild or moderate skin irritation. More frequent and more intense symptoms were observed on the left side (0.5%). Conclusion: Retinol in liquid crystal formulation is safe and provides significant clinical benefits associated with unification of skin colour, overall skin tone, skin elasticity, and moisture. Regular use of retinol typically results in brightening of the skin and reduced signs of ageing. The objective findings confirmed the effectiveness of the procedures.

MAS NMR Investigation of Molecular Order in an Ionic Liquid Crystal.

The structure and molecular order in the thermotropic ionic liquid crystal (ILC), [choline][geranate(H)octanoate], an analogue of Choline And GEranate (CAGE), which has potential for use as a broad-spectrum antimicrobial and transdermal and oral delivery agent, were investigated by magic-angle spinning (MAS) nuclear magnetic resonance (NMR), polarizing optical microscopy, small-angle X-ray scattering (SAXS), and mass spectrometry. Mass spectrometry and the 1H NMR chemical shift reveal that CAGE-oct is a dynamic system, with metathesis (the exchange of interacting ions) and hydrogen exchange occurring between hydrogen-bonded/ionic complexes such as [(choline)(geranate)(H)(octanoate)], [(choline)(octanoate)2(H)], and [(choline)(geranate)2(H)]. These clusters, which are shown by mass spectrometry to be significantly more stable than expected for typical electrostatic ion clusters, involve hydrogen bonding between the carboxylic acid, carboxylate, and hydroxyl groups, with rapid hydrogen bond breaking and re-formation observed to average the 1H chemical shifts. The formation of a partial bilayer liquid crystal (LC) phase was identified by SAXS and polarizing optical microscopy at temperatures below ∼293 K. The occurrence of this transition close to room temperature could be utilized as a potential temperature-induced “switch” of the anisotropic properties for particular applications. The presence of an isotropic component of approximately 23% was observed to coexist with the LC phase, as detected by polarizing optical microscopy and quantified by both 1H–13C dipolar-chemical shift correlation (DIPSHIFT) and 1H double-quantum (DQ) MAS NMR experiments. At temperatures above the LC-to-isotropic transition, intermediate-range order (clustering of polar and nonpolar domains), a feature of many ILs, persists. Site-specific order parameters for the LC phase of CAGE-oct were obtained from the MAS NMR measurement of the partially averaged 13C–1H dipolar couplings (DCH) by cross-polarization (CP) build-up curves and DIPSHIFT experiments, and 1H–1H dipolar couplings (DHH) by double-quantum (DQ) build-up curves. The corresponding order parameters, SCH and SHH, are in the range 0–0.2 and are lower compared to those for smectic (i.e., layered) phases of conventional nonionic liquid crystals, resembling those of lamellar phases formed by lyotropic surfactant–solvent systems.

Physical Properties of an Ionic Liquid Composed of Two Water-Soluble Vitamins and Enhanced Skin Permeation of Both Vitamins

A highly viscous substance was prepared by evaporating an ethanol solution containing two hydrophilic vitamins; vitamin C, and vitamin B6. The viscous substance and physical mixture of the two vitamins were tested using a differential scanning calorimeter and an X-ray diffractometer. The highly viscous substance was found to be a liquid crystal (LC) made of these two hydrophilic vitamins. Determination by proton nuclear magnetic resonance measurement suggested that intramolecular hydrogen bonding in vitamin B6 was eliminated by the LC formation. This LC compound showed high solubility in 1,3-butanediol (almost 87%). Much higher skin permeation of both vitamin C and B6 was also observed from the LC compound than that from the physical mixture. The present LC compound containing vitamin C and vitamin B6 may be useful for pharmaceutical and cosmeceutical applications.

Dissecting terminal fluorinated regulator of liquid crystals for fine-tuning intermolecular interaction and molecular configuration

Intermolecular interaction and molecular configuration are of great importance to the formation of liquid crystals (LCs). In this study, we have designed a fluorinated regulator at the end of LC molecules to investigate mesomorphic properties. Dissecting the terminal fluorinated regulator shows 4-fluoro substituent with a polar effect could promote dipole-dipole interaction, 2,6-difluoro substituent with a twist effect could facilitate steric molecular configuration, while 3,5-difluoro substituent with twist & polar effects could regulate not only molecular configuration and π-π interaction but also dipole-dipole interaction. From the independent and joint effects of the three regulating positions, it is concluded that intermolecular interactions (i.e., dipole-dipole interaction, π-π interaction and perfluoroarene-arene interaction) and molecular configuration can be effectively fine-tuned by the degree and pattern of fluorination. In addition, their thermal stabilities are evaluated systematically. These results will provide a further insight into LC molecule design.

Thermochromic Fibers via Electrospinning.

Cholesteryl ester liquid crystals exhibit thermochromic properties related to the existence of a twisted nematic phase. We formulate ternary mixtures of cholesteryl benzoate (CB), cholesteryl pelargonate (CP), and cholesteryl oleyl carbonate (COC) to achieve thermochromic behavior. We aim to achieve thermochromic fibers by incorporating the liquid crystal formulations into electrospun fibers. Two methods of incorporating the liquid crystal (LC) are compared: (1) blend electrospinning and (2) coaxial electrospinning using the same solvent system for the liquid crystal. For blend electrospinning, intermolecular interactions seem to be important in facilitating fiber formation since addition of LC can suppress bead formation. Coaxial electrospinning produces fibers with higher nominal fiber production rates (g/hr) and with higher nominal LC content in the fiber (wt. LC/wt. polymer assuming all of the solvent evaporates) but larger fiber size distributions as quantified by the coefficient of variation in fiber diameter than blend electrospinning with a single nozzle. Importantly, our proof-of-concept experiments demonstrate that coaxially electrospinning with LC and solvent in the core preserves the thermochromic properties of the LC so that thermochromic fibers are achieved.

Dynamic Collapse Mechanism of Alveolar Type 1 Caveolae Buds Modeled as Cubic Mesophase Lyotropic Liquid Crystal Formation and Growth

The alveolar type 1 (AT1) cells cover 95% of the cell surface area while the alveolar type 2 cells cover the remaining 5% of 100–150 m2 surface area of the lung. AT1 maintain membrane integrity by surface tension via caveolin proteins that stretch and collapse the membrane bilayer in physiological pressure cycling, however, collapse mechanics of the AT1 membrane have not been elucidated. Golani et al. modeled globular caveolin collapse structure base on mean curvature and lateral tension, and other sources have constructed similar models. The parameters are transformations of the critical packing parameter CPP equals monomer dimensions predicts that the monolayer shape of surfactants, described as v/al. Deng et al. model for gemini surfactants at the air‐water interface and Turner et al. model for the formation of caveolae bulbs via energy displacement of a membrane bound proteins have proposed similar geometric theories that show resemblance to lyotropic liquid crystal swell equation. The models feature common mathematical properties which are 1) spherical geometry, 2) lattice parameter‐based expansion, and 3) monomer population as mechanical descriptors of bilayer transformation. Each model correlated positively with cubic formation and decrease in surface tension. Krianeva et al. showed that monolayer of monoolein formed a new phase of bicontinuous phase, P4332, as the concentration of protein Horse cytochrome c increased. The spherical formation models predicted mesophases are cubic meaning that they are CPP >> 1, micellar cubic shape. The overall result, the caveolin bud shape is cubic bicontinuous mesophase, which is stabilized under physiological pressure cycling in the AT1 cell. We propose, the caveolin bud shape is a cubic bicontinuous mesophase stabilized under physiological pressure cycling in AT1 cell membrane and mechanics can be modeled by using the lamellar to cubic transition or the swelling law using change in surface tension vs lattice parameter as the formation rate. Furthermore, caveolin and cavin proteins present during the time of formation induce invagination, and, second, stabilization and fragility. Agarwal et al. show the transition phase between isotropic and cubic mesophase is a volume fraction difference of 0.05, a metastable polyhedral lattice produced by caveolin proteins, characterizing bud formation as plastic liquid crystal phase transition. This model could explain mechanoprotection by caveolae bud, and gives us a platform to think about self‐assembling monomer‐based medicines when approaching physical stretch dysfunction repair in the lung.Equations are models that describe cubic expansion from the lamellar setting across several membrane simulations. Equation 1 (left) describes the radius, r1, of Gemini surfactant. Equation 2 (middle) describes the formation of caveolae bulbs via the energy displacement of membrane‐bound proteins. Equation 3 (left) describes the swelling law of lyotropic mesophases.Figure 1

Luminescent Metallacycle-Cored Liquid Crystals Induced by Metal Coordination.

Two rhomboidal metallacycles based on metal-coordination-driven self-assembly are presented. Because metal-coordination interactions restrict the rotation of phenyl groups on tetraphenylethene units, these metallacycles were emissive both in solution and in solid state, and their aggregation-induced emission properties were well-retained. Moreover, the rhomboidal metallacyclic structures offer a platform for intermolecular packing beneficial for the formation of liquid crystalline phases. Therefore, although neither of building blocks shows mesogenic properties, both thermotropic and lyotropic (in DMF) mesophases were observed in one of metallacycles, indicating that mesophases could be induced by metal-coordination interactions. This study not only reveals the mechanism for the formation of cavity-cored liquid crystals, but also provides a convenient approach to preparing supramolecular luminescent liquid crystals, which will serve as good candidates for chemo sensors and liquid crystal displays.

From Equilibrium Liquid Crystal Formation and Kinetic Arrest to Photonic Bandgap Films Using Suspensions of Cellulose Nanocrystals

The lyotropic cholesteric liquid crystal phase developed by suspensions of cellulose nanocrystals (CNCs) has come increasingly into focus from numerous directions over the last few years. In part, this is because CNC suspensions are sustainably produced aqueous suspensions of a fully bio-derived nanomaterial with attractive properties. Equally important is the interesting and useful behavior exhibited by solid CNC films, created by drying a cholesteric-forming suspension. However, the pathway along which these films are realized, starting from a CNC suspension that may have low enough concentration to be fully isotropic, is more complex than often appreciated, leading to reproducibility problems and confusion. Addressing a broad audience of physicists, chemists, materials scientists and engineers, this Review focuses primarily on the physics and physical chemistry of CNC suspensions and the process of drying them. The ambition is to explain rather than to repeat, hence we spend more time than usual on the meanings and relevance of the key colloid and liquid crystal science concepts that must be mastered in order to understand the behavior of CNC suspensions, and we present some interesting analyses, arguments and data for the first time. We go through the development of cholesteric nuclei (tactoids) from the isotropic phase and their potential impact on the final dry films; the spontaneous CNC fractionation that takes place in the phase coexistence window; the kinetic arrest that sets in when the CNC mass fraction reaches ∼10 wt.%, preserving the cholesteric helical order until the film has dried; the ’coffee-ring effect’ active prior to kinetic arrest, often ruining the uniformity in the produced films; and the compression of the helix during the final water evaporation, giving rise to visible structural color in the films.

Synthesis of Platinum-Containing Conjugated Polymers Having QuinoxP* and Bipyridine Ligands. Chirality Transfer from the Phosphine Ligand to the Polymer Backbone

Platinum (Pt)-containing novel conjugated polymers, poly­(1-2a)–poly­(1-2d) having bipyridine ligands were synthesized by the Sonogashira–Hagihara coupling polymerization of [Pt­(4,4′-dibromo-2,2′-bipyridine)­((R,R)-2,3-bis­(tert-butylmethylphosphino)­quinoxaline)­(trifluoromethanesulfonate)2] (1) coordinated with 4,4′-dibromo-2,2′-bipyridine/(R,R)-2,3-bis­(tert-butylmethylphosphino)­quinoxaline [(R,R)-QuinoxP*] and 1,4-diethynylbenzene (2a), 1,4-diethynyl-2,5-bis­(heptyloxy)­benzene (2b), 1,4-diethynyl-2,5-bis­(2-ethylhexyloxy)­benzene (2c), and 1,4-diethynyl-2,5-bis­(2-(2-methoxyethoxy)­ethoxy)­benzene (2d). Poly­(1-2d) exhibited circular dichroism signals derived from (R,R)-QuinoxP* and the conjugated main chain around 290 and 440 nm in DMF, respectively. The simulated CD spectroscopic pattern of a low molecular model compound, M1-Pt, agreed well with the observed spectra. The TEM images of poly­(1-2d) in the solid state exhibited dispersed patterns with sizes around 10 nm. Concentrated solutions of polymer 1-2d in DMF and CHCl3 partly exhibited patterns assignable to the formation of lyotropic liquid crystals.

Optical effects in liquid crystal cell with photosensitive chalcogenide glass substrate

We report on the observation of dynamic light-induced annular patterns formation in a planar liquid crystal (LC) cell with chalcogenide microfilm As2S3 as orientating layer. The annular patterns appear under the irradiation of the cell by the laser beam (λ = 473 nm) with Gaussian distribution of intensity. The experimental results are explained in terms of the liquid crystal director reorientation in the LC cell after absorption of light by chalcogenide film. The director reorientation results in the LC refractive index change and formation of annular patterns in LC cell. To theoretically model the system under study we first minimized the total free energy functional subject to Gaussian-type modulation of the pretilt angle at chalcogenide covered substrate. Having found the director spatial profile we studied the light beam propagation through the cell with a spatially modulated pretilt angle. We determined the number of the aberration rings depending on the parameters of the laser beam and LC cell. We believe that light-induced change in the LC director anchoring at chalcogenide film can be applied to the development of various optical and electro-optical elements, such as dynamic micro-lenses, light controlled switchers and triggers, etc.

Ultra-tough and highly ordered macroscopic fiber assembly from 2D functional metal oxide nanosheet liquid crystals and strong ionic interlayer bridging.

Macroscopic assembly of 2D nanomaterials, especially for the one-dimensional macroscopic ordered fiber assembly from 2D liquid crystals (LCs), is rising to an unprecedented height and will continue to be an important topic in materials. However, this case of 2D functional metal oxide nanosheets is quite challenging. For the first time, the high-performance tungstate macroscopic fiber has been realized through an LC wet-spinning process involving the formation of LC colloid with spinnability and performance improvement by interlayer bridging in macroscopic assembly. The resultant macroscopic fiber yields record high tensile strength (198.5 MPa) and fracture toughness (3.0 MJ m-3) owing to their highly ordered structure and strong ionic interlayer bridging. Despite the intrinsically weak mechanical strength of the nanosheets, with only a few percent of graphene, the fibers manifest mechanical properties comparable to that of graphene fibers. Inspired by this concept, the possible macroscopic fibers assembled from other 2D functional metal oxide nanosheets will become a reality in the near future, holding great promise in aerospace and wearable applications.

Boundary Vortex Formation in Polarization-Modulated Orthogonal Smectic Liquid Crystals

We investigate the relaxation of an energy functional that originated in the physics literature to study the bistability of polarization modulated orthogonal smectic phases ${SmAP}_{{\tiny Fmod}}$ ...

DNA thermotropic liquid crystals controlled by positively charged catanionic bilayer vesicles

We report DNA thermotropic liquid crystal (TLC) formation by positively charged catanionic surfactant bilayer vesicles. The properties of DNA TLCs were found to be manipulated by both the chemical structures of cationic and anionic surfactants and the DNA amount. Positively charged catanionic bilayer vesicles bond to negative DNA sites resulting in the transition from vesicles to long range ordered lamellar crystals of DNA-catanionic surfactants, as confirmed by cryo- and freeze-fracture (FF) TEM observations and small-angle X-ray scattering (SAXS) measurements.

Predicting the effect of additives on wormlike micelle and liquid crystal formation and rheology with phase inversion phenomena

HypothesisSurfactant-based viscoelastic fluids are used in consumer products such as body wash, cosmetics, and in hydraulic fracturing fluids to suspend proppant, among others. The solubilization of oil within these fluids changes the curvature of the surfactant and their nanostructure and rheological properties. The curvature-based hydrophilic-lipophilic-difference + net-average-curvature (HLD-NAC) framework may be able to quantify curvature changes and predict the formulation conditions required to obtain viscoelasticity. ExperimentsPhase inversion experiments were conducted for combinations of commercial-grade C8, C10 and C12 tetrapropylene glycol ether sulfate (extended) surfactant and sodium dihexyl sulfosuccinate with oil to obtain the HLD-NAC parameters. Wormlike micelles (WLMs) and liquid crystals (LCs) were then formulated and characterized. The transition from spherical micelles to WLMs/LCs at different oil contents was identified and compared with phase transitions predicted via the HLD-NAC model. FindingsThe spherical micelle to branched WLM/LC transition in surfactant + oil systems coincided with the water-continuous (Type I) to bicontinuous (Type III) microemulsion phase transition predicted with the HLD-NAC model. Using this finding, the transition of commercial-grade sodium laureth sulfate (SLES) micelles to viscoelastic LCs containing various oils was predicted using the HLD-NAC. The HLD-NAC also predicted the presence of a secondary peak in viscosity obtained in “salt curves” experiments associated with branched WLMs and LCs.

Controlled release of a model hydrophilic high molecular weight compound from injectable non-lamellar liquid crystal formulations containing different types of phospholipids.

Skin offers an easily accessible and convenient site for the administration of drugs. Therefore, the development of injectable formulations with controlled drug release properties are now expected to deliver middle- and large-size biomolecules. In the present study, formulations mainly composed of a novel polyol ester with an isoprenoid side chain; mono-O-(5,9,13-trimethyl-4-tetradecenyl) glycerol ester (MGE), that was capable of forming a non-lamellar liquid crystal (NLLC), were prepared with different types of phospholipid. Then, factors that affected the release of a model entrapped drug, fluorescein-isothiocyanate dextran (FD-4, M.W. 4,000), from the MGE formulations were analyzed with multi-regression analysis. In addition, self-assembly of the NLLC structure was investigated using small-angle X-ray scattering analysis after contacting the MGE formulations with water. NLLC-forming ability of the formulations after s.c. injection into rats was also confirmed using microscopic observations. FD-4 concentrations in blood were determined after s.c. injection of the MGE formulations. The injectable MGE formulations successfully constructed NLLC structures to form a sponge-like gel after contact with water in vitro and in vivo (in rats) as well. In in vitro conditions, the amount of FD-4 released from the formulations was altered by changing the type and concentration of phospholipid in the MGE formulations and can be expressed with parameters such as MGE content and interplanar spacing of the NLLC. A significantly sustained FD-4 level in the blood was observed after s.c. injection of the formulations. These results suggested that injectable MGE formulations may have the potential to achieve controlled release profiles of drugs after s.c. injection.

Large Graphene Oxide Flakes: From Isotopic to Nematic Liquid Crystal Phase Transition

Herein, graphene oxide (GO) with large flakes of average size 38 μm is studied, following the isotropic–nematic phase transition over time and determining the critical concentration, i.e., the minimum value for the formation of the pure liquid crystal (LC) phase. The GO flakes in aqueous suspensions can form LC phases, which are attractive for various applications because of their exceptional properties. Stability over time is very important for their applications, especially, if the GO suspension is in the biphase concentration region in which a crucial change can occur—the isotropic LC phase separation. GO LCs have a wide biphase region, and even very low concentration suspensions appear purely nematic when prepared. However, over time, they appear to be biphasic and higher concentrations are needed for pure LC phase. The changes in the critical concentration were followed for over 4 months, and the findings indicate that it increases with time until it reaches a stable value that is, nevertheless, very low in concentration, 0.7 mg mL−1 (0.035 vol%). From the stable threshold volume fraction, the effective flake thickness, relevant in the LC phase formation behavior, is estimated. This value is almost double than what is measured by atomic force microscopy.

Tunable Dynamic Topological Defect Pattern Formation in Nematic Liquid Crystals

AbstractSoft materials are ideal candidates for the creation of tunable, self‐assembled structures. Herein, reconfigurable and switchable dynamic patterns are created using topological defects in nematic liquid crystals. The elastic properties of liquid crystals combined with their responsiveness to electric field are used to control the periodicity and the symmetry of an array of topological defects, assisted by polymeric micropillars. The switching between stable configurations is perfectly reversible and repeatable, and there is no limitation on the length scale of the regular array of defects. The array is used to create 2D diffraction patterns that can be tuned both in the azimuthal and in the polar directions. In addition, the refractive index of the liquid crystal mixture is controlled to optimize the diffraction efficiency. This system, with its flexibility and controllability, offers a promising route for the design of patters with arbitrary symmetry that can be employed in optics and reversible self‐assembly.

Formation of Polymer-Dispersed Nematic Liquid Crystals Doped by Nitrogen-Containing Carbon Nanotubes in Magnetic Field

Formation of Polymer-Dispersed Nematic Liquid Crystals Doped by Nitrogen-Containing Carbon Nanotubes in Magnetic Field

Topological defect enabled formation of nematic domains

ABSTRACTWe study numerically curvature and electric field driven domain formation and reorientations in two-dimensional nematic liquid crystals within square confinement. We use the Landau-de Gennes description in terms of the nematic tensor order parameter. We show that on increasing the amplitude of a sinusoidally shaped confining wall, pairs {defect, antidefect} are formed, which enable insertion of domains displaying significantly different average orientational order with respect to the surrounding nematic body. Furthermore, we study E-driven transformation between two competing degenerate domain-type structures. We show that transformations could be mediated via qualitatively different intermediate structures possessing topological defects.

Polymer-Brush-Decorated Graphene Oxide: Precision Synthesis and Liquid-Crystal Formation.

Given the specificity of the structure and function of graphene oxide (GO), hybridization with a variety of compounds will further extend its applications. To that end, we examined a new method for introducing a polymer brush onto the GO surface. In this method, GO was surface-modified with 2-((3-((2-bromo-2-methylpropanoyl)oxy)propyl)thio)ethylamine hydrochloride, which is a newly synthesized compound that contains an initiating group for atom transfer radical polymerization (ATRP) and an amino group for reacting with the epoxy groups on the GO surface. The ATRP-initiator-functionalized GO was then used as a substrate for the surface-initiated ATRP of methyl methacrylate (MMA), which produced graft polymers of poly(MMA) (PMMA) with targeted molecular weights and narrow molecular weight distributions; the average graft density was ∼0.06 chains/nm2. Because of their high dispersibilities and structural anisotropies, the PMMA-brush-decorated GOs formed lyotropic liquid crystals in their suspensions. In addition, similar suspensions with relatively high hybrid concentrations exhibited structural color that depended on the concentration.