Lyotropic Phase Research Articles

Ultrathin Uniform Platinum Nanowires via a Facile Route Using an Inverse Hexagonal Surfactant Phase Template.

We present an attractive method for the fabrication of long, straight, highly crystalline, ultrathin platinum nanowires. The fabrication is simply achieved using an inverse hexagonal (HII) lyotropic liquid crystal phase of the commercial surfactant phytantriol as a template. A platinum precursor dissolved within the cylindrical aqueous channels of the liquid crystal phase is chemically reduced by galvanic displacement using stainless steel. We demonstrate the production of nanowires using the HII phase in the phytantriol/water system which we obtain either by heating to 55 °C or at room temperature by the addition of a hydrophobic liquid, 9- cis-tricosene, to relieve packing frustration. The two sets of conditions produced high aspect nanowires with diameters of 2.5 and 1.7 nm, respectively, at least hundreds of nanometers in length, matching the size of the aqueous channels in which they grow. This versatile approach can be extended to produce highly uniform nanowires from a range of metals.

Lyotropic liquid crystals of CdS nanoribbons

Herein, we have observed the formation of highly ordered lyotropic liquid crystalline phase of CdS nanoribbons of different length scales. Solvent selectively wets the capping alkyl chains and induces mobility in them, this leads to the formation of the lyotropic liquid crystalline phase of these nanoribbons. We have characterized this self-organization by X-ray diffraction studies, polarized optical microscopy, differential scanning calorimetry, and Cryo-SEM techniques. Results indicate that these CdS nanoribbons aggregate in presence of cyclohexane to form rod like (Cds-50 and CdS-60) to rope like (CdS-70) supramolecular structures. These liquid crystals showed the presence of long-range orientational order and positional order. The majority of work on lyotropic liquid crystals has been confined to organic molecules, this study ventures into relatively less explored field of lyotropic phases in inorganic materials.

Morphologic Properties, Texture Transformations and Optical Refracting Properties: Aqueous Bicomponent Amphiphilic Lyotropic Systems

AbstractThe mesomorphic, morphologic and optical refracting properties of the bicomponent amphiphilic lyotropic systems have been investigated. Five amphiphiles with various concentration combinations as cationic – cationic, anionic – anionic and cationic – anionic lyotropic mixtures have been used for preparation of lyotropic systems. The mixtures were prepared with a constant (amphiphile1 + amphiphile2)/water concentration ratio. Isotropic lyotropic phase and hexagonal and lamellar lyotropic mesophases have been found in lyotropic systems under investigations. Dynamics of change of the magneto-morphologic properties vs. time, character of the heterophase regions of the mesophase – isotropic liquid phase transitions and temperature dependencies of the optical refracting properties of these bicomponent amphiphilic lyotropic systems have been investigated.

Thermal conductivity and rectification in asymmetric archaeal lipid membranes.

Nature employs lipids to construct nanostructured membranes that self-assemble in an aqueous environment to separate the cell interior from the exterior environment. Membrane composition changes among species and according to environmental conditions, which allows organisms to occupy a wide variety of different habitats. Lipid bilayers are phase-change materials that exhibit strong thermotropic and lyotropic phase behavior in an aqueous environment, which may also cause thermal rectification. Among different types of lipids, archaeal lipids are of great interest due to their ability to withstand extreme conditions. In this paper, nonequilibrium molecular dynamics simulations were employed to study the nanostructures and thermal properties of different archaeols and to investigate thermal rectification effects in asymmetric archaeal membranes. In particular, we are interested in understanding the role of bridged phytanyl chains and cyclopentane groups in controlling the phase transition temperature and heat flow across the membrane. Our results indicate that the bridged phytanyl chains decrease the molecular packing of lipids, whereas the existence of cyclopentane rings on the tail groups increases the molecular packing by enhancing the interactions between isoprenoid chains. We found that macrocyclic archaeols have the highest thermal conductivity, whereas macrocyclic archaeols with two cyclopentane rings have the lowest. The effect of the temperature on the variation of thermal conductivity was found to be progressive. Our results further indicate that small thermal rectification effects occur in asymmetric archaeol bilayer membranes at around 25 K temperature gradient. The calculated thermal rectification factor was around 0.09 which is in the range of rectification factor obtained experimentally for nanostructures such as carbon nanotubes (0.07). Such phenomena may be of biological significance and could also be optimized for use in various engineering applications.

Shape of Micelles and Temperature and Concentration Behavior of Optical Refractive Properties: Single Amphiphilic and Mixed Bicomponent Amphiphilic Lyotropic Systems

Lyotropic systems are bicomponent and/or multicomponent mixtures display physically isotropic and physically anisotropic properties and exhibit various types of isotropic lyotropic phases and anisotropic lyotropic mesophases. Structure units in lyotropic phases and mesophases are the nano-size three-dimensional nanoparticle supramolecular aggregates as the isometric and anisometric micelles. In this work, comparative investigations of the optical refractive properties of lyotropic micellar systems as mixtures of single amphiphile and mixed bicomponent amphiphiles in polar solvent have been carried out. Lauryltrimethyl ammonium bromide (LTAB) + water, cetyltrimethyl ammonium bromide (CTAB) + water, and (LTAB + CTAB mixture) + water lyotropic systems have been studied. Shapes of micelles in single component amphiphilic and bicomponent amphiphilic lyotropic systems have been estimated. Temperature and concentration dependences of the optical refractive index have been determined. Effect of the LTAB/CTAB concentration ratio on the refractive properties of mixtures under investigations has been found. Effect of length of the hydrophobic chain of amphiphile molecules with the same hydrophilic part on the refractive index of lyotropic systems is analysed.

Electroclinic effect in the chiral lamellar α phase of a lyotropic liquid crystal.

In thermotropic chiral Sm-A^{*} phases, an electric field along the smectic layers breaks the D_{∞} symmetry of the Sm-A^{*} phase and induces a tilt of the liquid crystal director. This so-called electroclinic effect (ECE) was first reported by Garoff and Meyer in 1977 and attracted substantial scientific and technological interest due to its linear and submicrosecond electro-optic response [S. Garoff and R. B. Meyer, Phys. Rev. A 19, 338 (1979)0556-279110.1103/PhysRevA.19.338]. We now report the observation of an ECE in the pretransitional regime from a lyotropic chiral lamellar L_{α}^{*} phase into a lyo-Sm-C^{*} phase, the lyotropic analog to the thermotropic Sm-C^{*} phase which was recently discovered by Bruckner etal. [Angew. Chem. Int. Ed. 52, 8934 (2013)1433-785110.1002/anie.201303344]. We further show that the observed ECE has all signatures of its thermotropic counterpart, namely (i) the effect is chiral in nature and vanishes in the racemic L_{α} phase, (ii) the effect is essentially linear in the sign and magnitude of the electric field, and (iii) the magnitude of the effect diverges hyperbolically as the temperature approaches the critical temperature of the second order tilting transition. Specific deviations between the ECEs in chiral lamellar and chiral smectic phases are related to the internal field screening effect of electric double layers formed by inevitable ionic impurities in lyotropic phases.

An Overview of Materials with Triply Periodic Minimal Surfaces and Related Geometry: From Biological Structures to Self-Assembled Systems.

Triply periodic minimal surface structures and related geometries are widely identified in many natural systems, such as biological membranes and biophotonic structures in butterfly-wing scales. Inspired by their marvelous and highly symmetrical structures and optimized physical properties, these structures have sparked immense interest for creating novel materials by extracting the design from nature. Significant progress has been made to understand these biological structures and fabricate artificial materials by top-down and bottom-up approaches for numerous applications in chemistry and materials science. Herein, research achievements, including theoretical and experimental discoveries, in both biological systems and the artificial synthesis of materials with triply periodic minimal surface structures and related materials are summarized. Recent developments in self-assembled lyotropic liquid crystal phases, block copolymer systems, and their inorganic replicas are discussed in detail.

Comparison between lyotropic cholesteric phase behavior with partly fluorinated surfactants and their exact hydrogenated counterparts

In this study, we examined lyotropic intrinsic cholesteric phase properties of some amino acid-based chiral surfactants, with partly fluorinated and hydrogenated chains, to investigate the effect of the twist structure of fluorocarbon chain on the helical twisting power of chiral surfactants. We synthesized some chiral and achiral surfactants, and their fluorinated/hydrogenated counterpart surfactants, taking into account the rule that [1 CF2=1.5 CH2]. We prepared lyotropic mixtures exhibiting discotic cholesteric phases by dissolution of chiral surfactants l-alaninehydrochloride undecylester (l-AUnDE), l-serinehydrochloride undecylester (l-SUnDE) and their partly fluorinated counterparts (l-APFOE and l-SPFOE, respectively) into sodium chloride (NaCl)/water mixtures, separately. The pitch measurements were used to evaluate the helical twisting powers of each fluorinated/hydrogenated chiral surfactants. The results indicated that the twist structure of fluorocarbon chain provides higher helical twisting power with respect to the hydrocarbon chain.

Lipids at the air–water interface

Lipids are important natural chemical compounds, as they comprise the major component in biological membranes. Biological membranes are composed of lipids in a bilayer structure and proteins incorporated into the bilayers or bound to the bilayer surface. Due to the amphiphilic nature of lipids, they self-assemble in aqueous solution into a variety of lyotropic phases, the most important one being the lamellar phase made up of stacks of lipid bilayers separated by water layers. The bilayer structure can be easily produced by dispersing lipids in water. Lipids are amphiphilic structures built up of a polar headgroup and one or two hydrophobic alkyl chains. They are, therefore, surface active and form the so-called insoluble monolayers or Langmuir films at the air–water interface. These monolayers resemble half of a lipid bilayer and are, therefore, widely used as model systems for bilayer membranes. In this review, the properties and the phase behavior of phospholipid monolayers, as well as the techniques used for studying these monolayers will be described. In addition, examples for the information gained using different techniques will be shown.

Incorporation of mRNA in Lamellar Lipid Matrices for Parenteral Administration.

Insertion of high molecular weight messenger RNA (mRNA) into lyotropic lipid phases as model systems for controlled release formulations for the mRNA was investigated. Low fractions of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) were used as an anchor to load the mRNA into a lamellar lipid matrix. Dispersions of zwitterionic lipid in the aqueous phase in the presence of increasing fractions of mRNA and cationic lipid were prepared, and the molecular organization was investigated as a function of mRNA and cationic lipid fraction. Insertion of both cationic lipid and mRNA was clearly proven from the physicochemical characteristics. The d-spacing of the lipid bilayers, as determined by small-angle X-ray scattering (SAXS) measurements, responded sensitively to the amount of inserted DOTAP and mRNA. A concise model of the insertion of the mRNA in the lipid matrices was derived, indicating that the mRNA was accommodated in the aqueous slab between lipid bilayers. Depending on the DOTAP and mRNA fraction, a different excess of water was present in this slab. Results from further physicochemical characterization, including determination of free and bound mRNA, zeta potential, and calorimetry data, were in line with this assumption. The structure of these concentrated lipid/mRNA preparations was maintained upon dilution. The functionality of the inserted mRNA was proven by cell culture experiments using C2C12 murine myoblast cells with the luciferase-encoding mRNA. The described lipid phases as carriers for the mRNA may be applicable for different routes of local administration, where control of the release kinetics and the form of the released mRNA (bound or free) is required.

Phase Boundaries, Optical Refraction and Specific Electrical Conductivity Properties in Lyotropic Micellar L1 Phase: Bicomponent Amphiphilic (DDTMABr + HDTMABr) + Water System

Abstract In this work, complex investigations of the temperature and concentration behaviour of the optical refraction properties and specific electrical conductivity properties in lyotropic micellar L1 phase have been carried out. Bicomponent amphiphilic (DDTMABr + HDTMABr) + water lyotropic systems with various DDTMABr/HDTMABr concentration ratios have been objects of our investigations. The phase diagram for L1 phase in this system has been determined. Effect of the DDTMABr/HDTMABr concentration ratios on the refractive index and specific electrical conductivity has been observed. The mutual influence of amphiphile with short alkyl chain (DDTMABr) and long alkyl chain (HDTMABr) on the phase states, refractive index and electrical conductivity properties has been found. Our results show that variation of the concentration ratio in a mixture of amphiphiles with different length of the non-polar tail gives possibility to regulate the hydrophilicity degree, optical density, refraction properties and specific electrical conductivity of mixed lyotropic systems.

Engineering the interface between lipid membranes and nanoporous gold: A study by quartz crystal microbalance with dissipation monitoring.

Nanoporous gold (np-Au) is a nanostructured metal with many desirable attributes. Despite the growing number of applications of nanoporous materials, there are still open questions regarding their fabrication and subsequent surface functionalization. For example, the hydrophobic nature of gold surfaces makes the formation of planar supported lipid layers challenging. Here, the authors engineer the interface between np-Au and 1,2-dioleoyl-sn-glycero-3-phosphocholine lipid layers using well-differentiated approaches based on vesicle adsorption and solvent exchange methods. The results reveal that the nanotopography of the np-Au surface plays a clear role in the vesicle adsorption process. Compared to vesicle adsorption, the solvent exchange method proves successful in the formation of planar supported lipid bilayers in both np-Au and planar Au surfaces, being less sensitive to the surface morphological features. The influence of nanostructured surfaces on lipid layer formation is determined by the driving mechanisms behind each process, i.e., the balance of adhesion and cohesion forces in vesicle adsorption and lyotropic lipid phase transitions in solvent exchange, respectively. A better understanding of such interactions will contribute to the development of a variety of applications, from electrochemical biosensors to drug screening and delivery systems, using nanoporous gold coated with stimuli-responsive lipid layers.

Effect of viscosity, pH and physicochemical parameters of solvent on the aggregation and dielectric behaviour of lyotropic liquid crystals binary mixtures

This paper reports on the synthesis of lyotropic liquid crystalline phases using cetyl pyridinium chloride and sodium dodecyl sulphate in the aqueous (water) and non-aqueous solvent (glycerol) of varying polarity and viscosities. Various crystal-like, liquid-like and liquid crystalline phases are seen in the different solvent media at the expense of increasing concentration of surfactants. It is interesting to highlight that highly viscous and little acidic (pH≈6) mixtures produce more ordered structures comparing to other. Aggregation of cetyl pyridinium chloride in both solvents is found thermally driven process as calorimetric transition confirmed the growth of the lyotropic phases at a higher temperature (331–345K) than 303K. Quenching has been evolved as the proficient technique to bring the higher temperature lyotropic liquid crystalline ordering to the room temperature without breaking the symmetry. Structural and polarizing optical microscopy measurement reveals that viscosity plays vital role on the aggregation in lyotropic liquid crystalline systems as glycerol based quenched and as-synthesized lyotropic liquid crystalline phases are found more ordered than other. Dielectric dynamics reveals that quenched cetyl pyridinium chloride/glycerol-based lyotropic liquid crystalline phases show higher dielectric constant; however, the reverse is true for the sodium dodecyl sulphate/glycerol lyotropic liquid crystalline phases. Dc conductivity of the order 10−5S/m is one of the significant finding of this study, which open up the application perspective of these phases.

Structural Investigation of Bulk and Dispersed Inverse Lyotropic Hexagonal Liquid Crystalline Phases of Eicosapentaenoic Acid Monoglyceride.

Recent studies demonstrated the potential therapeutic use of newly synthesized omega-3 (ω-3) polyunsaturated fatty acid (PUFA) monoglycerides owing to their beneficial health effects in various disorders including cancer and inflammation diseases. To date, the research was mainly focused on exploring the biological effects of these functional lipids. However, to the best of our knowledge, there is no report on the hydration-mediated self assembly of these lipids that leads to the formation of nanostructures, which are attractive for use as vehicles for the delivery of drugs and functional foods. In the present study, we investigated the temperature-composition phase behaviour of eicosapentaenoic acid monoglyceride (MAG-EPA), which is one of the most investigated ω-3 PUFA monoglycerides, during a heating-cooling cycle in the temperature range of 5-60 °C. Experimental synchrotron small-angle X-ray scattering (SAXS) evidence on the formation of a dominant inverse hexagonal (H2) lyotropic liquid crystalline phase and its temperature-induced transition to an inverse micellar solution (L2 phase) is presented for the fully hydrated bulk MAG-EPA system and its corresponding dispersion. We produced colloidal MAG-EPA hexosomes with an internal inverse hexagonal (H2) lyotropic crystalline phase in the presence of F127, a well-known polymeric stabilizer, or citrem, which is a negatively charged food-grade emulsifier. In this work, we report also on the formation of MAG-EPA hexosomes by vortexing MAG-EPA in excess aqueous medium containing F127 at room temperature. This low-energy emulsification method is different than most reported studies in the literature that have demonstrated the need for using a high-energy input during the emulsification step or adding an organic solvent for the formation of such colloidal nonlamellar liquid crystalline dispersions. The designed nanoparticles hold promise for future drug and functional food delivery applications due to their unique structural properties and the potential health-promoting effects of MAG-EPA.

Complex three-dimensional self-assembly in proxies for atmospheric aerosols

Aerosols are significant to the Earth’s climate, with nearly all atmospheric aerosols containing organic compounds that often contain both hydrophilic and hydrophobic parts. However, the nature of how these compounds are arranged within an aerosol droplet remains unknown. Here we demonstrate that fatty acids in proxies for atmospheric aerosols self-assemble into highly ordered three-dimensional nanostructures that may have implications for environmentally important processes. Acoustically trapped droplets of oleic acid/sodium oleate mixtures in sodium chloride solution are analysed by simultaneous synchrotron small-angle X-ray scattering and Raman spectroscopy in a controlled gas-phase environment. We demonstrate that the droplets contained crystal-like lyotropic phases including hexagonal and cubic close-packed arrangements of spherical and cylindrical micelles, and stacks of bilayers, whose structures responded to atmospherically relevant humidity changes and chemical reactions. Further experiments show that self-assembly reduces the rate of the reaction of the fatty acid with ozone, and that lyotropic-phase formation also occurs in more complex mixtures more closely resembling compositions of atmospheric aerosols. We suggest that lyotropic-phase formation likely occurs in the atmosphere, with potential implications for radiative forcing, residence times and other aerosol characteristics.

Transfection of plasmid DNA by nanocarriers containing a gemini cationic lipid with an aromatic spacer or its monomeric counterpart

This study performed a biophysical characterization (electrochemistry, structure and morphology) and assessment of the biological activity and cell biocompatibility of GCL/DOPE-pDNA lipoplexes comprised of plasmid DNA and a mixed lipid formed by a DOPE zwitterionic lipid and a gemini cationic lipid N-N′-(1,3-phenylene bis (methylene)) bis (N,N-dimethyl-N-(1-dodecyl) ammonium dibromide (12PH12) containing an aromatic spacer or its monomeric counterpart surfactant, N-benzyl-N,N-dimethyl-N-(1-dodecyl) ammonium bromide (12PH). Electrochemical results reveal that i) the gemini cationic lipid (12PH12) and the plasmid pDNA yield effective charges less than their nominal charges (+2 and −2/bp, respectively) and that ii) both vectors (12PH12/DOPE and 12PH/DOPE) could compact pDNA and protect it from DNase I degradation. SAXS and cryo-TEM experiments indicate the presence of a lamellar lyotropic liquid crystal phase represented as alternating layers of mixed lipid and plasmid. Transfection efficiency (by FACS and luminometry) and cell viability assay in COS-7 cells, performed with two plasmid DNAs (pEGFP-C3 and pCMV-Luc VR1216), confirm the goodness of the proposed formulations (12PH12/DOPE and 12PH/DOPE) to transport genetic material, with efficiencies and biocompatibilities comparable to or better than those exhibited by the control Lipofectamine 2000*. In conclusion, although major attention has been paid to gemini cationic lipids in the literature, due to the large variety of modifications that their structures may support to improve the biological activity of the resulting lipoplexes, it is remarkable that the monomeric counterpart surfactant with an aromatic group analyzed in the present work also exhibits good biological activity. The in vitro results reported here indicate that the optimum formulations of the gene vectors studied in this work efficiently transfect plasmid DNA with very low toxicity levels and, thus, may be used in forthcoming in vivo experiments.

Effect of dicationic ionic liquids on lyotropic liquid crystals formed by a binary system composed of Triton-X 100 and water

ABSTRACTIn this work, binary mixtures of a non-ionic surfactant (Triton X-100) and water were studied with concentrations of 30%wt H2O, showing, lamellar mesophase at temperatures below 10oC. Different dicationic ionic liquids were used for doping these mesophases: 1,n-bis(3-methylimidazolium-1-yl)alkane, 1,n-bis(1-methylpyrrolidinium-1-yl)alkane and 1,n-bis(pyridinium-N-yl)alkane dibromide, where n = 6 and 8. Polarized Optical Microscopy and Small-Angle X-ray Scattering were used for identifying the mesophases and the influence of different dicationic ionic liquids on the lyotropic liquid crystals phase transitions. The addition of dicationic ionic liquids to the lyotropic liquid crystals samples led to changes in transition temperature and in mesophase structure itself (such as characteristic distances).

Stabilization of Collagen Fibrils by Gelatin Addition: A Study of Collagen/Gelatin Dense Phases

Collagen and its denatured form, gelatin, are biopolymers of fundamental interest in numerous fields ranging from living tissues to biomaterials, food, and cosmetics. This study aims at characterizing mixtures of those biopolymers at high concentrations (up to 100 mg·mL-1) at which collagen has mesogenic properties. We use a structural approach combining polarization-resolved multiphoton microscopy, polarized light microscopy, magnetic resonance imaging, and transmission electron microscopy to analyze gelatin and collagen/gelatin dense phases in their sol and gel states from the macroscopic to the microscopic scale. We first report the formation of a lyotropic crystal phase of gelatin A and show that gelatin must structure itself in particles to become mesogenic. We demonstrate that mixtures of collagen and gelatin phase segregate, preserving the setting of the pure collagen mesophase at a gelatin ratio of up to 20% and generating a biphasic fractal sample at all tested ratios. Moreover, differential scanning calorimetric analysis shows that each protein separates into two populations. Both populations of gelatins are stabilized by the presence of collagen, whereas only one population of collagen molecules is stabilized by the presence of gelatin, most probably those at the interface of the fibrillated microdomains and of the gelatin phase. Although further studies are needed to fully understand the involved mechanism, these new data should have a direct impact on the bioengineering of those two biopolymers.

Structural and dielectric behaviors of Bi4Ti3O12 – lyotropic liquid crystalline nanocolloids

ABSTRACTWe investigated the structural and dielectric dynamics of nanocolloids comprising lyotropic liquid crystals and bismuth titanate (Bi4Ti3O12) spherical nanoparticles (≈16–18 nm) of varying concentration 0.05 and 0.1 wt%. The lyotropic liquid crystalline mixture was prepared by a binary mixture of cetylpyridinuium chloride and ethylene glycol mixed in 5:95 wt% ratio. Binary lyotropic mixture exhibited hexagonal lyotropic phase. Structural and textural characterizations of nanocolloids infer that the nanoparticles were homogeneously dispersed in the liquid crystalline matrix and did not perturb the hexagonal ordering of the lyotropic phase. The dielectric constant and dielectric strength were found to be increased with the rise in the Bi4Ti3O12 nanoparticles concertation in the lyotropic matrix. A significant increase of one order was observed in the ac conductivity of colloidal systems as compared to the non-doped lyotropic liquid crystal. Relaxation parameters of the non-doped lyotropic liquid crystal and colloidal systems were computed and correlated with other parameters.

Physicochemical Evaluation of Micellar Solution and Lyotropic Phases Formed by Self-Assembled Aggregates of Morpholinium Geminis.

The micellar solution and the lyotropic liquid crystalline phases formed by gemini surfactants containing morpholinium headgroups are investigated for their self-aggregation and physicochemical properties in water. These gemini surfactants demonstrated good surface activity because they are able to undergo micellization at lower concentration and form nanosized micellar aggregates in dilute aqueous solution. The binary mixture of the morpholinium gemini surfactant–water system is investigated over a wide range of concentrations. The micellar solution of the morpholinium gemini surfactants demonstrated Newtonian fluidlike behavior between 10 and 50 wt % as the observed viscosities were independent of the applied shear rate. At higher concentration, morpholinium geminis formed self-assembled lyotropic phases in water. These liquid crystalline phases were characterized by small-angle X-ray scattering and polarized optical microscopy techniques.