Use of the ternary phase diagram of a mixed cationic/glucopyranoside surfactant system to predict mesostructured silica synthesis

Mixed surfactant systems have the potential to impart controlled combinations of functionality and pore structure to mesoporous metal oxides. Here, we combine a functional glucopyranoside surfactant with a cationic surfactant that readily forms liquid crystalline mesophases. The phase diagram for the ternary system CTAB/H(2)O/n-octyl-beta-D-glucopyranoside (C(8)G(1)) at 50 degrees C is measured using polarized optical microscopy. At this temperature, the binary C(8)G(1)/H(2)O system forms disordered micellar solutions up to 72 wt% C(8)G(1), and there is no hexagonal phase. With the addition of CTAB, we identify a large area of hexagonal phase, as well as cubic, lamellar and solid surfactant phases. The ternary phase diagram is used to predict the synthesis of thick mesoporous silica films via a direct liquid crystal templating technique. By changing the relative concentration of mixed surfactants as well as inorganic precursor species, surfactant/silica mesostructured thick films can be synthesized with variable glucopyranoside content, and with 2D hexagonal, cubic and lamellar structures. The domains over which different mesophases are prepared correspond well with those of the ternary phase diagram if the hydrophilic inorganic species is assumed to act as an equivalent volume of water.     

Tuning in-meso-crystallized lysozyme polymorphism by lyotropic liquid crystal symmetry

Lipid-based lyotropic liquid crystals (LLCs) show great potential for applications in fields as diverse as food technology, cosmetics, pharmaceutics, or structural biology. Recently, these systems have provided a viable alternative to the difficult process of membrane protein crystallization, owing to their similarities with cell membranes. Nonetheless, the process of in-meso crystallization of proteins still remains poorly understood. In this study, we demonstrate that in-meso crystal morphologies of lysozyme (LSZ), a model hydrophilic protein, can be controlled by both the composition and symmetry of the mesophase, inferring a possible general influence of the LLC space group on the protein crystal polymorphism. Lysozyme was crystallized in-meso from three common LLC phases (lamellar, inverse hexagonal, and inverse bicontinuous cubic) composed of monolinolein and water. Different mixing ratios of mesophase to crystallization buffer were used in order to tune crystallization both in the bulk mesophase and in excess water conditions. Two distinct mechanisms of crystallization were shown to take place depending on available water in the mesophases. In the bulk mesophases, protein nuclei form and grow within structural defects of the mesophase and partially dehydrate the system inducing order-to-order transitions of the liquid crystalline phase toward stable symmetries in conditions of lower hydration. The formed protein crystals eventually macrophase separate from the mesophase allowing the system to reach its final symmetry. On the other hand, when excess water is available, protein molecules diffuse from the water channels into the excess water, where the crystallization process can take place freely, and with little to no effect on the structure and symmetry of the lyotropic liquid crystals.     

A single parameter determines mesophase transitions in Swollen Liquid Crystals

We report how the control of a single parameter, the co-surfactant, determines the phase transitions of oil-in-water swollen liquid crystals (SLCs) prepared with cetyltrimethylammonium bromide (CTAB), from cubic to hexagonal, lamellar, and finally sponge-like structures. SLCs are complex mixtures (surfactant + co-surfactant + water + salt + oil) usually prepared to form hexagonal mesophases, with cell parameters tunable between 3 and 30 nm. These hexagonal mesophases were successfully used as nanoreactors to prepare a broad range of nanostructured materials. Because the potential of these mesophases as adaptive nanoreactors has not been extended to other liquid crystal geometries than the hexagonal, we studied in a first step the structure evolution of SLCs made with CTAB, cyclohexane, pentanol-1, water and different stabilising salts. We used small-angle X-ray scattering (SAXS), polarised light microscopy and Freeze-Fracture TEM to provide a partial phase diagram and list the different mesophases obtained as a function of composition. We report that the adjustment of a single parameter, the co-surfactant (pentanol-1), determines the phase transition between cubic, hexagonal, lamellar, and sponge-like structures, all other parameters such as the nature and concentration of salt, or amount of oil being constant.     

"Sponge" nanoparticle dispersions in aqueous mixtures of diglycerol monooleate, glycerol dioleate, and polysorbate 80

Lipid nanoparticles of nonlamellar lyotropic phases have a wide solubilizing and encapsulating spectrum for a range of substances thanks to their nanostructured interior featuring both lipophilic and hydrophilic domains. As a consequence, these systems have emerged as promising drug delivery systems in various pharmaceutical and diagnostic applications. Here we present the phase behavior and dispersion properties of a novel three-component lipid system composed of diglycerol monooleate (DGMO), glycerol dioleate (GDO), and polysorbate 80 (P80) which shows several advantageous features relating to drug delivery applications including: spontaneous dispersion formation with a narrow size distribution and tunable particle phase-structure. The obtained phase diagram shows the presence of lamellar (L(alpha)), hexagonal (H(2)), and reverse bicontinuous cubic (V(2)) liquid crystalline phases and an inverse micellar (L(2)) solution. A particularly interesting observation is the presence of a phase region where two liquid phases coexist, most likely the L(2) and L(3) ("sponge phase"). These two phase structures appear also to coexist in the submicron particles formed in the dilute water region, where the L(3) element appears to stabilize nanoparticles with inner L(2) structure. Increasing the fraction of the dispersing P80 component results in the growth of the more water rich L(3) "surface phase" at the expense of the size of the inner L(2) core.     

Physicochemical Characterization and Rheological Behavior Evaluation of the Liquid Crystalline Mesophases Developed with Different Silicones

This article presented physicochemical characterization and rheological behavior evaluation of the liquid crystalline mesophases developed with different silicones. There were prepared 5 ternary systems, which were carried out the determination of the relative density, the electric conductivity and polarized light microscopy analysis, being selected two systems to promote the Preliminary Stability Tests. The results showed that System 1 obtained the major liquid crystal formation and a higher stability. The temperature influences in the systems stability and phases structure. In hot oven, observed oneself the mixture of lamellar and hexagonal phase, for both systems.     

Lyotropic liquid crystalline phases formed in ternary mixtures of 1-cetyl-3-methylimidazolium bromide/p-xylene/water: a SAXS, POM, and rheology study

The phase behavior of ternary mixtures of 1-cetyl-3-methylimidazolium bromide (C(16)mim-Br)/p-xylene/water is studied by small-angle X-ray scattering (SAXS), polarized optical microscopy (POM), and rheology measurements. Two types of lyotropic liquid crystalline phases are formed in the mixtures: hexagonal and lamellar. The structural parameters of the lyotropic liquid crystalline phases are calculated. Greater surfactant content in the sample leads to denser aggregation of the cylindrical units in the hexagonal liquid crystalline phase. The increase in lattice parameter and thickness of the water layer in lamellar phase are attributed to the increase of water content, and the area per surfactant molecule at the hydrophobic/hydrophilic interface for lamellar phase is found to be larger than that for hexagonal phase. The structural parameters of the liquid crystalline phases formed from the cetyltrimethylammonium bromide (CTAB) system are larger than those for the C(16)mim-Br system. The rheological properties of the samples are also found to be related to the structure of the liquid crystalline phases.     

Self-assembly approach toward magnetic silica-type nanoparticles of different shapes from reverse block copolymer mesophases

In the present study poly(isoprene-block-ethylene oxide), PI-b-PEO, block copolymers are used to structure iron oxide and silica precursors into reverse mesophases, which upon dissolution of the organic matrix lead to well-defined nanoparticles of spheres, cylinders, and plates based on the original structure of the mesophase prepared. The hybrid mesophases with sphere, cylinder, and lamellar morphologies containing the inorganic components in the minority phases are characterized through a combination of small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), and electron energy loss spectroscopy (EELS). After heat treatments the respective nanoparticles on mica surfaces are characterized by scanning force microscopy (SFM). X-ray diffraction (XRD) and superconducting quantum interference device (SQUID) magnetometer measurements are performed to demonstrate that the heat treatment leads to the formation of a magnetic gamma-Fe2O3 crystalline phase within the amorphous aluminosilicate. The results pave the way to functional, i.e., magnetic nanoparticles where the size, shape, and iron oxide concentration can be controlled opening a range of possible applications.     

Phase behavior of an extended surfactant in water and a detailed characterization of the concentrated phases

The formation of microemulsions with triglycerides at ambient conditions can be improved by increasing the surfactant-water and surfactant-oil interactions. Therefore, extended surfactants were developed, which contain hydrophilic/lipophilic linkers. They have the ability to stretch further into the oil and water phase and enhance the solubility of oil in water. In this work, the phase behavior of a chosen extended surfactant (C(12-14)-PO(16)-EO(2)-SO(4)Na, X-AES) in H(2)O/D(2)O at high surfactant concentrations (30-100 wt %) and at temperatures between 0 and 90 °C is studied for the first time. The lyotropic liquid crystals formed were determined by optical microscopy, small-angle X-ray scattering (SAXS), and (2)H and (23)Na NMR, and a detailed phase diagram of the concentrated area is given. The obtained mesophases are a hexagonal phase (H(1)), at low temperatures and small concentrations, a lamellar phase (L(α)) at high temperatures or concentrations, a bicontinuous cubic phase (V(2)) as well as a reverse hexagonal phase (H(2)). To our knowledge, this is the first surfactant that forms both H(1) and H(2) phases without the addition of a third compound. From the (2)H NMR quadrupole splittings of D(2)O, we have examined water binding in the L(α) and the H(2) phases. There is no marked difference in the bound water between the two phases. Where sufficient water is present, the number of bound water molecules per X-AES is estimated to be ca. 18 with only small changes at different temperatures. Similar results were obtained from the (23)Na NMR data, which again showed little difference in the ion binding between the L(α) and the H(2) phases. The X-ray diffraction data show that X-AES has a much smaller average length in the L(α) phase compared to the all-trans length than in the case for conventional surfactants. At very high surfactant concentrations an inverse isotropic solution (L(2)), containing a small fraction of solid particles, is formed. This isotropic solution is clearly identified and the size of the reversed micelles was determined using (1)H NMR measurements. Furthermore, the solid particles within the L(2) phase and the neat surfactant were analyzed. The observed results were compared to common conventional surfactants (e.g., sodium dodecyl sulfate, sodium lauryl ether sulfate, and sodium dodecyl-p-benzene sulfonate), and the influence of the hydrophilic/lipophilic linkers on the phase behavior was discussed.     

Nonaqueous lyotropic liquid-crystalline phases formed by gemini surfactants in a protic ionic liquid

The aggregation behaviors of three Gemini surfactants [(C(s)H(2s)-α,ω-(Me(2)N(+)C(m)H(2m+1)Br(-))(2), s = 2, m = 10, 12, 14] in a protic ionic liquid, ethylammonium nitrate (EAN), have been investigated. The polarized optical microscopy and small-angle X-ray scattering (SAXS) measurements are used to explore the lyotropic liquid crystal (LLC) formation. Compared to the LLCs formed in aqueous environment, the normal hexagonal and lamellar phases disappear. However, with increasing the surfactant concentration, a new reverse hexagonal phase (H(II)) can be mapped over a large temperature range except for other ordered aggregates including the isotropic solution phase and a two-phase coexistence region. The structural parameters of the H(II) are calculated from the corresponding SAXS patterns, showing the influence of surfactant amount, alkyl chain length, and temperature. Meanwhile, the rheological profiles indicate a typical Maxwell behavior of the LLC phases formed in EAN.     

Liquid crystalline bolaamphiphiles with semiperfluorinated lateral chains: competition between layerlike and honeycomb-like organization

Novel bolaamphiphilic triblockmolecules consisting of a rigid biphenyl unit, with a polar 2,3-dihydroxypropyloxy group and a phenolic OH group at opposite ends, as well as a semiperfluorinated chain in a lateral position have been synthesized via palladium catalyzed cross coupling reactions as the key steps. The thermotropic liquid crystalline behavior of these compounds was investigated by polarized light microscopy, DSC and X-ray scattering, and the influence of the length of the lateral chain on the mesomorphic properties was studied. The compound with the shortest chain as well as the long chain derivatives form lamellar mesophases composed of segregated layers of the bolaamphiphilic moieties and sublayers comprising the fluid lateral chains. The layers within the lamellar phases of the short chain compound adopt a positional correlation, leading to a 2D lattice (Col(r)/p2mm), whereas the layers of the lamellar phases of the long chain derivatives are noncorrelated (Lam). Compounds with a medium chain length organize into columnar phases, where the nonpolar lateral chains segregate into columns, which are embedded in networks of regular (Col(h)) or stretched (Col(r)/c2mm) hexagonal cylinder shells consisting of the bolaamphiphilic units. In total, an unusual phase sequence was found, where, with respect to the chain length, columnar mesophases occur between two mesophases with layer organization.     

Determination of water content in internally self-assembled monoglyceride-based dispersions from the bulk phase

We determined the water intake of internally structured oil-loaded monoglyceride-based dispersions. This was possible through small-angle X-ray scattering (SAXS) experiments on the corresponding bulk mesophases because the structural parameters in full hydration conditions are identical to those of the dispersed particles. From low water contents to full hydration, the bulk phases depend strongly on the amount of oil. At room temperature in excess water and with increasing oil concentration, successive bicontinuous cubic, reverse hexagonal, micellar cubic, and inverse micellar-type isotropic fluid phases are found. The solubilized water is determined as a function of the oil content for each phase, and it is found to range from 5-33 wt %.     

Self-assembly of ternary cubic, hexagonal, and lamellar mesophases using the lattice-Boltzmann kinetic method

We use a kinetic lattice-Boltzmann method to simulate the self-assembly of the cubic primitive (P), diamond (D), and gyroid (G) mesophases from an initial quench composed of oil, water, and amphiphilic particles. Here, we also report the self-assembly of the noncubic hexagonal phase and two lamellar phases, one with periodic convolutions. The periodic mesophase structures are emergent from the underlying conservation laws and quasi-molecular interactions of the lattice-Boltzmann model. We locate regions of the model's parameter space where the sequence of appearance of mesophases lamellar --> primitive --> hexagonal is in agreement with pressure jump experiments and the sequence cubic --> lamellar is in agreement with compositional variations reported in the literature. The ability of our lattice-Boltzmann model to simulate self-assembly of cubic and noncubic phases in a unified and consistent manner opens the way for further investigations into the transition pathways and kinetics of the phase transitions between these states as well as of the rheology of these phases.     

LYOTROPIC LIQUID CRYSTALS IN BINARY SYSTEMS N-ALKYL GLYCOSIDES/WATER*

The formation of lyotropic mesophases (liquid crystals) in four binary systems n-alkyl glycosides/water was examined in dependence on surfactant concentration, temperature and the chain lengths (alkyl = heptyl, octyl, nonyl, decyl). The binary phase diagrams were established and the enthalpies of phase transitions were measured. The following phase transitions were detected by texture observation and calorimetry: hexagonal phase H, lamellar phase L, cubic phase Q, gel phase G and crystalline phase C. The positions of the corresponding regions of these phases in the phase diagram were determined. Sequence of phases and the localization of the phase regions were depended on the chain length of the alkyl group. So in the binary system n-decyl-β-D-glucoside/water the H-phase was not observed.     

SAXS investigation of a cubic to a sponge (L3) phase transition in self-assembled lipid nanocarriers

The encapsulation and release of peptides, proteins, nucleic acids, and drugs in nanostructured lipid carriers depend on the type of the self-assembled liquid-crystalline organization and the structural dimensions of the aqueous and membraneous compartments, which can be tuned by the multicomponent composition of the systems. In this work, small-angle X-ray scattering (SAXS) investigation is performed on the 'melting' transition of the bicontinuous double diamond cubic phase, formed by pure glycerol monooleate (MO), upon progressive inclusion of varying fractions of pharmaceutical-grade glycerol monooleate (GO) in the hydrated system. The self-assembled MO/GO mixtures are found to form diamond (Pn3m) inverted cubic, inverted hexagonal (H(II)), and sponge (L(3)) phases at ambient temperature in excess of aqueous medium without heat treatment. Mixing of the inverted-cubic-phase-forming MO and the sponge-phase-forming GO components, in equivalent proportions (50/50 w/w), yields an inverted hexagonal (H(II)) phase nanostructured carrier. Scattering models are applied for fitting of the experimental SAXS patterns and identification of the structural changes in the aqueous and lipid bilayer subcompartments. The possibility of transforming, at ambient temperature (20 °C), the bicontinuous cubic nanostructures into inverted hexagonal (H(II)) or sponge (L(3)) mesophases may facilitate novel biomedical applications of the investigated liquid crystalline self-assemblies.     

Fragmentation of the lamellae and fractionation of polymer coils upon mixing poly(dimethylacrylamide) with the lamellar phase of aerosol OT in water

The lamellar mesophase formed by surfactant 1,4-bis(2-ethylhexyl) sodium sulfosuccinate (AOT) in deuterated water is mixed with poly(dimethylacrylamide) (PDMAA) polymers of low molecular weight (Mn= (2-20) x 10(3)). The mixtures separate into microphases (lamellar plus isotropic polymer solution). Their microstructures are studied by microscopy, small-angle X-ray scattering (SAXS), and deuterium NMR (2H NMR). According to SAXS, the lamellar phase fractionates the molecular weight distribution of the polymer, by dissolving only chains with coil sizes smaller than the thickness of the water layers between lamellae, and keeping larger chains segregated from the lamellar phase. The fraction of polymer that is segregated from the lamellar phase grows with Mn of the polymer. In 2H NMR, there are two signals, a quadrupolar doublet (water molecules hydrating the anisotropic lamellar phase contribute to this doublet) and a singlet (water molecules in the isotropic polymer solution contribute to this singlet). These two signals are deconvoluted to analyze the phases. Mixing with the polymer produces the partial dispersion of the lamellar phase into small fragments (microcrystallites). The structure of these microcrystallites is such that they conserve the regular long period spacing of the macrophase, and are thus identified in SAXS, but they are smaller than the minimum size required to produce quadrupolar splitting (about 4 microm), and therefore, in 2H NMR, they contribute to the singlet. 2H NMR can thus not distinguish between small microcrystallites and an isotropic polymer solution segregated from the lamellar phase; instead small microcrystallites are detected as an apparent increase of the isotropic solution. The degree of dispersion produced by the polymer in the lamellar phase is correlated with the degree of segregation that the polymer suffers. Thus, much greater dispersion into microcrystallites is produced by the higher Mn polymers than by the lower Mn polymers (in the range covered by the present samples, although with a much higher molecular weight sample (3 x 10(6)) that is totally segregated no such microcrystallites were detected).     

Phase behavior of a DNA-based surfactant mixed with water and n-alcohols

The self-assembly behavior of a cationic surfactant (dodecyltrimethylammonium, DTA) with DNA as counterion in mixtures of water and n-alcohols (decanol, octanol, hexanol, butanol, and ethanol) was investigated. The phase diagrams were established and the different regions of the phase diagram characterized with respect to microstructure by (2)H NMR, small-angle X-ray scattering (SAXS), and other techniques. The DNA-DTA surfactant is soluble in all of the studied alcohols, showing increased solubility from decanol down to ethanol. All of the phase diagrams are analogous with respect to the occurrence of liquid crystalline (LC) regions, but the area of the LC region increases as one goes from decanol to ethanol. In all phase diagrams, hexagonal phases (of the reversed type) for the alcohol-rich side and lamellar phases for the other side were detected. For balanced proportions of the components, there is a coexistence of the lamellar and the hexagonal phase, here detected with a double quadrupole splitting in the (2)H NMR spectra. The correctness of the phase diagrams is confirmed by the fact that along the tie-lines the splitting magnitude remains nearly constant. All of the alcohols except for ethanol act as cosurfactants penetrating the DNA-DTA film. Adding salt to the ternary mixtures causes an increase in the unit cell dimension of the lamellar and the hexagonal phases. The phase diagram becomes more complicated when butanol is used for the alcohol phase. Here, there is the occurrence of a new isotropic phase with some properties analogous to those of the disordered sponge (L3) phase obtained for simple surfactant systems.     

Monomeric and dimeric anionic surfactants: A comparative study of self-aggregation and mineralization

A study on the phase behavior and structure of the alkanolamine salts of the dimeric amphiphile 3,4-bis-dodecyloxycarbonyl-hexanedioic acid (GS-H) is presented for the first time. Data are compared to those of the corresponding monomeric surfactant (lauric acid, LA). The alkanolamine salts of GS-H show very low Krafft points (<0 °C) and form hexagonal liquid crystals at concentrations lower than its monomeric counterpart, indicating that aggregation is favored for dimeric surfactants. The minimum concentration for liquid crystal formation increases for bulky alkanolamines with a structure-disrupting effect, such as triethanolamine (TEA). However, the specific surface areas per molecule in the liquid crystals derived from small-angle X-ray scattering (SAXS) are similar for monoethanolamine (MEA) and TEA salts; the same can be said when comparing monomeric (LA) and dimeric (GS-H) salts. GS-H can also form hexagonal and lamellar liquid crystals with organic aminosilanes acting as reactive counterions, as revealed by solvent penetration experiments with polarized optical microscopy (POM). Consequently, mineralization with silica and alumina was carried out by a sol–gel method using GS-H as a possible structure-directing agent. Both silica and alumina samples possessed a lamellar structure, which disappears on calcination; however, calcined alumina has indeed a high surface area coming mainly from micropores. It was found that the surfactant/aminosilane ratio is critical for obtaining structured silica before calcination.     

A structural study of the mesophases of two oxyethylene alkyl ether-decane-water systems,a comparison between technical grade C12EO〈7〉 and pure C12EO6

As part of a study polyoxyethylene alkyl ethers (C _m EO _n ), water and decane, the phase diagram and the structures of the mesophases of pure C₁₂EO₆ and technical grade C₁₂EO₇ were compared. The constructed phase diagrams of the two systems show a great resemblance except for one difference: the viscous isotropic phase is only present in the C₁₂EO₆ phase diagram.The swelling behavior of the lamellar and hexagonal phases was studied with smallangle x-ray scattering. Both the lamellar and hexagonal phases showed an ideal swelling behavior and no differences between the lamellar and hexagonal phases of the two systems were detected.With freeze-fracture electron microscopy the hexagonal and lamellar phases were visualized. No differences in the textures of the lamellar phases were found, however, the micrographs of the hexagonal phases of the two systems clearly showed different textures. While in the hexagonal phase of the C₁₂EO₆ system only infinite long rods were visualized, short interrupted rods were found in the hexagonal phase of the C₁₂EO₇ system.     

Influence of glycerol on the formation of lyotropic mesophases —microscopic texture observations for determining preliminary phase diagrams of binary K-soap/glycerol systems

Analogously to aqueous K-soap/water systems already examined, the glycerol-containing systems KC _n /G (KC _n ;n=12, 14, 16, 18, 22; G=glycerol) are also able to build up hexagonal, lamellar, optically isotropic, gel-like and crystalline phases. These preliminary phases have been identified by texture observations of contact samples and singular concentrations with a polarizing microscope. The appertaining phase regions have been plotted in the binary phase diagrams.Correspondences and differences between these systems have been elucidared by drawing a comparison. Mosaic texture and oily streaks are typical of the lamellar phase. Spherulites are mainly found in the heterogeneous two-phase region lamellar/isotropic. The textures of the hexagonal phase are of fan-like morphology. The appearance of the gel phase texture resembles globular or curd-like structures.The influences exerted by the increasing chain lengths of the K-soaps (KC _n ,n=12–22) on the phase regions in the binary systems (KC _n /G) can be described as follows. The concentrations required for forming the hexagonal and the lamellar phase respectively are shifted toward lower K-soap concentrations. The concentration range in which the hexagonal phase is stable is diminished. The temperature range in which the hexagonal phase is stable becomes larger. The upper temperature limit of the lamellar phase region is lowered.Binary aqueous and glycerol-containing K-soap systems have the following common features: The hexagonal phase is built up at low soap concentrations. The lamellar phase is formed at high soap concentrations. The lamellar phase is formed at high soap concentrations. An optically isotropic region is inserved between the lamellar and the hexagonal phase in aqueous and glycerol-containing systems of the types KC₁₄, KC₁₆ and KC₁₈. The temperature of the transition hexagonalisotropic phase (HS) runs through a maximum value. On increasing the chain length the formation of the hexagonal phase is shifted in the direction of lower soap concentrations.Aqueous and glycerol-containing K-soap mixtures differ in the following essential points: The lyotropic mesophases (H, L, I) of aqueous systems are formed at considerably lower soap concentrations than the corresponding phases of glycerol-containing systems. The lamellar phases of aqueous systems reach the regions of very low soap concentrations. The lyotropic mesophases of aqueous systems are built up at temperatures lower than the corresponding ones of glycerol-containing mixtures. In aqueous systems the concentration range of the lamellar phase increases with increasing chain length, in contrast to glycerol-containing systems where it is diminished.     

Understanding the interfacial properties of nanostructured liquid crystalline materials for surface-specific delivery applications

Nonlamellar liquid crystalline dispersions such as cubosomes and hexosomes have great potential as novel surface-targeted active delivery systems. In this study, the influence of internal nanostructure, chemical composition, and the presence of Pluronic F127 as a stabilizer, on the surface and interfacial properties of different liquid crystalline particles and surfaces, was investigated. The interfacial properties of the bulk liquid crystalline systems with coexisting excess water were dependent on the internal liquid crystalline nanostructure. In particular, the surfaces of the inverse cubic systems were more hydrophilic than that of the inverse hexagonal phase. The interaction between F127 and the bulk liquid crystalline systems depended on the internal liquid crystalline structure and chemical composition. For example, F127 adsorbed to the surface of the bulk phytantriol cubic phase, while for monoolein cubic phase, F127 was integrated into the liquid crystalline structure. Last, the interfacial adsorption behavior of the dispersed liquid crystalline particles also depended on both the internal nanostructure and the chemical composition, despite the dispersions all being stabilized using F127. The findings highlight the need to understand the specific surface characteristics and the nature of the interaction with colloidal stabilizer for understanding and optimizing the behavior of nonlamellar liquid crystalline systems in surface delivery applications.