Lyotropic Liquid Crystalline Phases Research Articles

Scalable weak aligning medium for enantiodiscrimination of water soluble chiral molecules

The study reports the first indication of a lyotropic liquid crystalline phase of an aqueous solution of polysaccharide xanthan gum, as a physical parameter dependent scalable and reversible weak alignment medium, for enantiodiscrimination of water soluble chiral molecules.

Nonionic diethanolamide amphiphiles with unsaturated C18 hydrocarbon chains: thermotropic and lyotropic liquid crystalline phase behavior

The neat and lyotropic liquid crystalline phase behavior of three nonionic diethanolamide amphiphiles with C18 hydrocarbon chains containing one, two or three unsaturated bonds has been examined. This has allowed the effect of degree of unsaturation on the phase behavior of diethanolamide amphiphiles to be investigated. Neat linoleoyl and linolenoyl diethanolamide undergo a transition from a glassy liquid crystal to a liquid crystal at ∼-85 °C, while neat oleoyl diethanolamide undergoes a transition at ∼-60 °C to a liquid crystalline material before re-crystallizing at -34 °C. Oleoyl diethanolamide then undergoes a third transition from a crystalline phase to a smectic liquid crystalline phase at ∼5 °C. In the absence of water, the transition temperature from a smectic liquid crystal to an isotropic liquid decreases with increasing unsaturation. The addition of water results in the formation of a lamellar phase (L(α)) for all three amphiphiles. The lamellar phase is stable under excess water conditions up to temperatures of at least 70 °C. Approximate partial binary amphiphile-water phase diagrams generated for the three unsaturated C18 amphiphiles indicate that the excess water point for each amphiphile occurs at ∼60% (w/w) amphiphile.

Nanostructured self-assembly materials from neat and aqueous solutions of C18 lipid pro-drug analogues of Capecitabine—a chemotherapy agent. Focus on nanoparticulate cubosomes™ of the oleyl analogue

A series of prodrug analogues based on the established chemotherapy agent, 5-fluorouracil, have been prepared and characterized. C18 alkyl and alkenyl chains with increasing degree of unsaturation were attached to the N4 position of the 5-fluorocytosine (5-FC) base via a carbamate bond. Physicochemical characterization of the prodrug analogues was carried out using a combination of differential scanning calorimetry, cross-polarized optical microscopy, X-ray diffraction and small-angle X-ray scattering. The presence of a monounsaturated oleyl chain was found to promote lyotropic liquid crystalline phase formation in excess water with a fluid lamellar phase observed at room temperature and one or more bicontinuous cubic phases at 37 °C. The bulk phase was successfully dispersed into liposomes or cubosomes at room and physiological temperature respectively. In vitro toxicity of the nanoparticulate 5-FCOle dispersions was evaluated against several normal and cancer cell types over a 48 h period and exhibited an IC50 of ∼100 μM against all cell types. The in vivo efficacy of 5-FCOle cubosomes was assessed against the highly aggressive mouse 4T1 breast cancer model and compared to Capecitabine (a water-soluble commercially available 5-FU prodrug) delivered at the same dosages. After 21 days of treatment, the 0.5 mmol 5-FCOle treatment group exhibited a significantly smaller average tumour volume than all other treatment groups including Capecitabine at similar dosage. These results exemplify the potential of self-assembled amphiphile prodrugs for delivery of bioactives in vivo.

Aqueous phase behaviour of choline carboxylate surfactants—exceptional variety and extent of cubic phases

Choline carboxylate surfactants are powerful alternatives to the well-known classical alkali soaps, since they exhibit substantially increased water solubility while maintaining biocompatibility, in contrast to simple quaternary ammonium ions. In the present study, we report the aqueous binary phase diagrams and a detailed investigation of the lyotropic liquid crystalline phases formed by choline carboxylate surfactants (ChCm) with chain lengths ranging from m = 12–18 and at surfactant concentrations of up to 95–98 wt%. The identification of the lyotropic mesophases and their sequence was achieved by the penetration scan technique. Structural details are elucidated by small-angle X-ray scattering (SAXS). The general sequence of mesophases with increasing soap concentration was found to be as follows: micellar (L1), discontinuous cubic (I1), hexagonal (H1), bicontinuous cubic (V1) and lamellar (Lα). The main difference to the phase behavior of alkali soaps or of other mono-anionic surfactants is the appearance and large extent of a discontinuous cubic phase with two or even more different symmetries. The obtained phase diagrams further highlight the extraordinarily high water solubility of ChCm soaps. Finally, structural parameters of ChCm salts such as the cross-sectional area at the polar–nonpolar interface are compared to those of alkali soaps and discussed in the terms of specific counterion binding and packing constraints.

Aqueous phase behavior of ionic liquid-related gemini surfactant revealed by differential scanning calorimetry and polarized optical microscopy

An aqueous phase behavior was investigated for ionic liquid-related cationic gemini surfactant, [C12im-4-C12im][Br2], in which two dodecylimidazolium parts are linked by a spacer composed of four methylene units. Differential scanning calorimetry was used to detect phase boundaries among various phases, from which a temperature−composition (T−X) phase diagram was constructed. Lyotropic liquid-crystalline phases appearing in this mixture were characterized by means of polarized optical microscopy. It was revealed that (1) two types of liquid-crystalline phases, lamellar ( $$ {{\hbox{L}}_\alpha } $$ ) and hexagonal (H1), are formed; (2) H1 phase coexists with micellar solution (L1) over a wide concentration range from a few wt.% to ca. 80 wt.% of the surfactant; and (3) the hydrated solid with the composition of [C12im-4-C12im][Br2]·2H2O exhibits incongruent melting point at which the hydrated solid decomposes into H1 phase and unhydrated surfactant solid.

Assessment of the Validity of the Double Superhelix Model for Reconstituted High Density Lipoproteins: A COMBINED COMPUTATIONAL-EXPERIMENTAL APPROACH

For several decades, the standard model for high density lipoprotein (HDL) particles reconstituted from apolipoprotein A-I (apoA-I) and phospholipid (apoA-I/HDL) has been a discoidal particle ∼100 Å in diameter and the thickness of a phospholipid bilayer. Recently, Wu et al. (Wu, Z., Gogonea, V., Lee, X., Wagner, M. A., Li, X. M., Huang, Y., Undurti, A., May, R. P., Haertlein, M., Moulin, M., Gutsche, I., Zaccai, G., Didonato, J. A., and Hazen, S. L. (2009) J. Biol. Chem. 284, 36605-36619) used small angle neutron scattering to develop a new model they termed double superhelix (DSH) apoA-I that is dramatically different from the standard model. Their model possesses an open helical shape that wraps around a prolate ellipsoidal type I hexagonal lyotropic liquid crystalline phase. Here, we used three independent approaches, molecular dynamics, EM tomography, and fluorescence resonance energy transfer spectroscopy (FRET) to assess the validity of the DSH model. (i) By using molecular dynamics, two different approaches, all-atom simulated annealing and coarse-grained simulation, show that initial ellipsoidal DSH particles rapidly collapse to discoidal bilayer structures. These results suggest that, compatible with current knowledge of lipid phase diagrams, apoA-I cannot stabilize hexagonal I phase particles of phospholipid. (ii) By using EM, two different approaches, negative stain and cryo-EM tomography, show that reconstituted apoA-I/HDL particles are discoidal in shape. (iii) By using FRET, reconstituted apoA-I/HDL particles show a 28-34-Å intermolecular separation between terminal domain residues 40 and 240, a distance that is incompatible with the dimensions of the DSH model. Therefore, we suggest that, although novel, the DSH model is energetically unfavorable and not likely to be correct. Rather, we conclude that all evidence supports the likelihood that reconstituted apoA-I/HDL particles, in general, are discoidal in shape.

Nanostructured Nonionic Thymidine Nucleolipid Self-Assembly Materials

Three nucleoside lipids have been synthesized: 3'-oleoylthymidine, 3',5'-dioleoylthymidine, and 3'-phytanoylthymidine. Differential scanning calorimetry and X-ray diffraction have been employed to characterize the physical properties of these neat lipids. Polarizing optical microscopy, small-angle X-ray scattering, and cryo-transmission electron microscopy techniques have been used to investigate the phase behavior in aqueous systems. Both oleoyl-based nucleoside lipids adopted a lamellar crystalline phase in the neat form at room temperature, and the phytanoyl derivative exhibited a fluid isotropic phase. Under excess water conditions, the presence of one branched (phytanoyl) or one unsaturated (oleoyl) chain promoted the formation of a liquid-crystalline lamellar phase at physiological temperatures. In contrast, the 3',5'-dioleoylthymidine derivative is nonswelling and does not exhibit lyotropic liquid-crystalline phase behavior. The nucleolipids' propensity for DNA-type binding and recognition has been evaluated by using a monolayer system to measure surface pressure-area isotherms in a Langmuir trough and indicates that the nucleoside base is available for nonspecific hydrogen bonding in the monolayer liquid expanded state for the single-chain nucleolipids but not for the dual-chain amphiphile.

The influence of dipalmitoyl phosphatidylserine on phase behaviour of and cellular response to lyotropic liquid crystalline dispersions

Lyotropic liquid crystalline nanoparticles (cubosomes) have the potential to act as amphiphilic scaffolds for the presentation of lipids and subsequent application in, for example, bioseparations and therapeutic delivery. In this work we have formulated lyotropic liquid crystalline systems based on the synthetic amphiphile 1,2,3-trihydroxy-3,7,11,15-tetramethylhexadecane (phytantriol) and containing the lipid dipalmitoyl phosphatidylserine (DPPS). We have prepared a range of DPPS-containing phytantriol cubosome formulations and characterized them using Small Angle X-ray Scattering and Cryo-transmission electron microscopy. These techniques show that increased DPPS content induces marked changes in lyotropic liquid crystalline phase behaviour, characterized by changes in crystallographic dimensions and increases in vesicle content. Furthermore, in vitro cell culture studies indicate that these changes correlate with lipid/surfactant cellular uptake and cytotoxicity. A model cell membrane based on a surface supported phospholipid bilayer was used to gain insights into cubosome–bilayer interactions using Quartz Crystal Microgravimetry. The data show that mass uptake at the supported bilayer increased with DPPS content. We propose that the cytotoxicity of the DPPS-containing dispersions results from changes in lipid/surfactant phase behaviour and the preferential attachment and fusion of vesicles at the cell membrane.

Optically Active Lyotropic Chromonic Liquid Crystal Based on Green Perylene Bisimide

Recently, PBIs having ionic periphery have attracted much attention since they can form lyotropic chromonic liquid crystal-line (LCLC) phase in aqueous solution. In the LCLC phase, the molecules form a self-assembled columnar structure due to the π-π stacking of aromatic core and the hydrophilic interaction of ionic peripheries at water interface. A growing acceptance of the concept of chromonic phases and a wider recognition that they form a well-defined family of lyotropic liquid crystalline (LC) phases with variety of properties make the LCLCs distinct in almost every aspect from conventional lyotropic liquid cry-stals such as amphiphiles.

Synthesis of a Polymerizable Fluorosurfactant for the Construction of Stable Nanostructured Proton-Conducting Membranes

The synthesis of the polymerizable fluorinated surfactant sodium 1,1,2,2-tetrafluoro-2-(1,1,2,2-tetrafluoro-2-(4-vinylphenyl)ethoxy)ethanesulfonate (1) and a number of related fluorocarbon compounds is described. Compound 1 is synthesized using a copper-mediated cross-coupling reaction of 4-bromobenzaldehyde and sodium 5-iodooctafluoro-3-oxapentanesulfonate. The resulting benzaldehyde is converted to a styrene unit using a Wittig reaction with methyltriphenylphosphonium bromide in acetonitrile, using DBU as a base. This strategy for converting an iodo-functionalized fluorosurfactant to a styrene-containing fluorosurfactant is highly efficient because both reactions are performed in polar solvents and are compatible with the sulfonate moiety. In addition, the copper-mediated cross-coupling reaction is most efficient with electron-poor aryl bromides like 4-bromobenzaldehyde. We wish to employ 1 for the construction of nanostructured membranes by polymerization of 1 in a microemulsion or in lyotropic liquid crystalline phases.

Synthesis and characterization of nanostructured Cu/ZnO/Al2O3 from lyotropic liquid crystalline templates

Abstract The hexagonal lyotropic liquid crystalline phases of nonionic surfactants AEO-9 were used to template directly the fabrication of nanostructured Cu/ZnO/Al2O3 oxides. The reaction between metal precursors and alkaline reacting substance dissolved within the aqueous domains of the liquid crystalline templates generated nanostructured oxides. Low-angle X-ray diffraction and transmission election microscopy characterization reveals the product as a hexagonal array of cylindrical pores with pore-to-pore separation of ca. 6.3 nm. Possessing ordered nanochannels, Cu/ZnO/Al2O3 oxides could find more potential application in catalysis.

Liquid Crystalline Phases of the Amphiphilic Ionic Liquid N-Hexadecyl-N-methylpyrrolidinium Bromide Formed in the Ionic Liquid Ethylammonium Nitrate and in Water

The phase behavior of a surfactant-like ionic liquid, N-hexadecyl-N-methylpyrrolidinium bromide (C(16)MPB), was studied in both water and a room temperature ionic liquid, ethylammonium nitrate (EAN). Polarized optical microscopy (POM) and small-angle X-ray scattering (SAXS) measurements were employed to investigate the phase behavior of the two systems and to determine which lyotropic liquid crystalline (LC) phases were formed. With increasing C(16)MPB concentration, an isotropic solution phase, a hexagonal (H(1)) phase, and a cubic phase (V(2)) are all present in either EAN or H(2)O. The structural parameters of the H(1) phase were calculated from SAXS patterns, which show the structural changes as a function of the amount of C(16)MPB. The rheological results reveal that the H(1) phase constructed by C(16)MPB in EAN displays a typical Maxwell behavior, whereas the H(1) phase formed by C(16)MPB in water shows a gel-like behavior, unlike traditional cationic surfactants. POM and differential scanning calorimetry (DSC) results demonstrate that the lyotropic LC phase in EAN has a higher thermal stability than that formed in H(2)O, which may be important to extend the applications of the LC phase.

Lyotropic liquid crystalline phases formed in binary mixture of 1-tetradecyl-3-methylimidazolium chloride/ethylammonium nitrate and its application in the dispersion of multi-walled carbon nanotubes

The phase behavior of a surfactant-like ionic liquid 1-tetradecyl-3-methylimidazolium chloride (C 14mimCl) in a room-temperature ionic liquid ethylammonium nitrate (EAN) is studied. The lyotropic liquid crystalline (LLC) phases formed in the binary mixture are thoroughly investigated by polarized optical microscopy (POM) and small-angle X-ray scattering (SAXS) measurements, and the temperature effect on the LC phases is also elucidated. Then, a hexagonal (H 1) LC phase was used to disperse multi-walled carbon nanotubes (MWCNTs). Both POM images and SAXS patterns indicate that, the dispersion of MWCNTs cannot break the structure of H 1 phase. By comparing the rheological properties before and after dispersing, it could be found that the incorporation of MWCNTs has increased the viscosity of H 1 phase.

Ordered micellar and inverse micellar lyotropic phases

In this article we review the ordered micellar and inverse micellar lyotropic liquid-crystalline phases that can be formed by amphiphilic molecules such as lipids and surfactants. We focus first on the self-assembly of amphiphiles into aggregates, and then consider the interfacial curvature and the role of curvature elasticity and packing constraints in determining the allowed structures. We then review the range of ordered micellar and inverse micellar phases that have so far been observed in a variety of surfactant and lipid systems. Finally, we describe certain characteristic properties, such as the epitaxy between phases, and the self-diffusion and electrical conductivity within such ordered micellar phases.

Voltammetric Determination of Glucose at Bismuth‐Modified Mesoporous Platinum Microelectrodes

AbstractMesoporous platinum microeletrodes (MPtEs) modified by a mono‐ or submonolayer of adsorbed bismuth (Bi‐MPtE) were investigated and employed for the detection of glucose in 0.2 M NaOH solutions. The mesoporous platinum films were electrodeposited from hexachloroplatinic acid dissolved in the aqueous domain of the lyotropic liquid crystalline phase of octaethylene glycol monohexadecyl ether. Bismuth ad‐atoms were obtained by under potential deposition of Bi3+ ions in 0.5 M H2SO4 solutions. The coverage of the MPtEs by irreversibly adsorbed bismuth was checked in either a 0.5 M H2SO4 or 0.2 M NaOH solution free of Bi3+ ions, and exploiting the charge involved in the hydrogen adsorption/desorption peaks, which decreased in proportion to the amount of platinum sites covered by bismuth. The catalytic activity of a series of Bi‐MPtEs towards the oxidation of glucose was investigated by cyclic voltammetry, and the overall behaviour was found to be superior of that of the corresponding MPtEs. Also, at Bi‐MPtEs, the effect of interference by ascorbic acid was minimal. Calibration plots were examined over the glucose concentration range from 0.5 mM to 300 mM. It was found that linearity, between current against glucose concentration, and sensitivity depended on the electrode type and real surface area. At the Bi‐MPtEs both linear range and sensitivity were larger than those of the MPtEs. These results were discussed in terms of high tolerance of the Bi‐MPtEs towards the intermediate poisons originated in the electrooxidation process of glucose.

LineardsDNA Partitions Spontaneously into the Inverse Hexagonal Lyotropic Liquid Crystalline Phases of Phospholipids

Recently, we reported that DNA associated with inverse hexagonal (H(II)) lyotropic liquid crystal phases of the lipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) was actively transcribed by T7 RNA polymerase. Our findings suggested that key components of the transcription process, probably the T7 RNA polymerase and the DNA, remained associated with the monolithic H(II) phase throughout transcription. Here, we investigate the partitioning of DNA between an H(II) lyotropic liquid crystal phase and an isotropic supernatant phase in order to develop insights into the localization of DNA in liquid crystalline environments. Our results show that linear double stranded DNA (dsDNA) molecules partition spontaneously into monolithic preformed H(II) liquid crystal phases of DOPE. We propose that this process is driven by the increase in entropy due to the release of counterions from the DNA when it inserts into the aqueous pores of the H(II) phase.

Lyotropic Liquid Crystalline Self-Assembly in Dispersions of Silver Nanowires and Nanoparticles

We report demixed nematic lyotropic liquid crystalline phase formation in dispersions of silver nanowires and spherical nanoparticle aggregates in ethylene glycol and water. This phase is observed in samples in spite of the high density, large aspect ratio, and long relaxation times of the nanowires which have an average length of 6.8 microm. Remarkably, in the biphasic region, the nanowire-rich liquid crystalline phase exhibits a strandlike morphology which has only previously been reported for single-walled carbon nanotube liquid crystals. Shearing predominantly liquid crystalline dispersions results in both significant nanowire alignment and nanowire-aggregate demixing. The results of this research suggest that the nanoparticle contaminants common to many synthesis schemes facilitate liquid crystalline phase formation and that these dispersions can be processed into aligned coatings.

Liquid crystalline phases of 1,2-dimethyl-3-hexadecylimidazolium bromide and binary mixtures with water

1,2-Dimethyl-3-hexadecylimidazolium bromide, which lacks an acidic proton at the C-2 imidazolium ring position, exhibits thermotropic SmA 2 phase behavior above its melting point of 90.3 °C and up to 232.1 °C. The corresponding layer spacing and the full width at half maximum from XRD patterns display a temperature dependence. In binary mixtures with water, over a concentration range of 40–75%, lyotropic liquid crystalline phases form between 0.5 and 25 °C. The molecules of the new ionic liquid (IL) in the binary mixtures show three different self-assembly processes, namely, formation of rod micelles, coexistence of rod micelles and a hexagonal phase, and a pure hexagonal phase. The distance between the two centers of adjacent columns of cylinder units remains nearly constant at 4.97 ± 0.04 nm when the IL content exceeds 70%, indicating that the cylinder units attain a dense and highly ordered packing.

Instant synthesis of mesoporous monolithic materials with controllable geometry, dimension and stability: a review

The development of the nanoscale structures and their integration into components, systems, and natural architectures (such as monoliths), and large-scale devices, is one of the most promising areas in the emerging field of nanotechnology. We believe that it is time to write a review that focused on the rapid synthesis and the functional properties of HOM mesoporous monoliths. Thus, we here introduce comprehensive and up-to-date reports on the instant synthesis (within minutes) of a range of mesoporous silica monoliths (HOM-type, High-Order-Monolith) by means of a direct-templating method of lyotropic and microemulsion liquid crystalline phases. A number of nonionic n-alkyl-oligo(ethylene oxide), namely, Brij-type (CxEOy), and Triton- and Tween-type and cationic alkyl trimethylammonium bromide or chloride (CnTMA-B or -C, where n = 12, 14, 16 and 18) surfactants were used as soft templates. A variety of 1D, 2D and 3D mesostructure geometries were successfully fabricated by using this simple, fast and yet reproducible design strategy. This is the first and detailed review of using rapid synthesis to fabricate disordered and ordered silica/surfactant mesophases with supermicro- and meso-pore engineering systems. In this review, we also addressed the prominent factors affected the formation of the large-scale ordered and worm-like structures (HOM): (1) the phase composition of domains, (2) the extent of solubilization of hydrocarbons, and (3) the nature of surfactant molecules (corona/core features). Significantly, due to large morphological particle sizes, these HOM monolithic structures exhibited considerable structural stability against longer hydrothermal treatment times. Such retention is crucial in industrial applications.

Charge Reversal of the Rodlike Colloidal fd Virus through Surface Chemical Modification

There is increasing interest in the use of viruses as model systems for fundamental research and as templates for nanomaterials. In this work, the rodlike fd virus was subjected to chemical modifications targeting different solvent-exposed functional groups in order to tune its surface properties, especially reversing the surface charge from negative to positive. The carboxyl groups of fd were coupled with different kinds of organic amines by carbodiimide chemistry, resulting in modified viruses that are positively charged over a wide range of pH. Care was taken to minimize intervirus cross linking, which often occurs because of such modifications. The surface amino groups were also grafted with poly(ethylene glycol) (PEG) end-functionalized with an active succinimidyl ester in order to introduce a steric stabilization effect. By combining charge reversal with PEG grafting, a reversible attraction between positively and negatively charged PEG-grafted fd viruses could be realized, which was tuned by the ionic strength of the solution. In addition, a charge-reversed fd virus forms only a pure nematic phase in contrast to the cholesteric phase of the wild type. These modified viruses might be used as model systems in soft condensed matter physics, for example, in the study of polyelectrolyte complexes or lyotropic liquid-crystalline phase behavior.