Partial Ternary Phase Diagram Research Articles

Influence of Li-Salt on the Mesophases of Pluronic Block Copolymers in Ionic Liquid.

We study the complex mixture of a polyethylene oxide-b-polypropylene oxide-b-polyethylene oxide triblock copolymer (Pluronic F127) with ionic liquid (IL) and Li-salt, which is potentially interesting as an electrolyte system with decoupled mechanical and ion-transport properties. Small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) are employed to scrutinize the phase structures and elucidate the ternary phase diagram. These data are combined with the ion diffusivities obtained by pulsed field gradient (PFG) nuclear magnetic resonance (NMR). Analyzing the partial ternary phase diagram of F127/LiTFSI/Pyr14TFSI, hexagonal, lamellar, and micellar mesophases are identified, including two-phase coexistence regions. While the PPO block is immiscible with the liquid, and forms the backbone of the mesostructured aggregates, the PEO blocks are not well miscible with the IL. Poorly solvated, the latter may still crystallize. At a higher IL content, PEO is further solvated, but a major solvation effect occurs due to addition of Li-salt. Li ions promote solubilization of the PEO chains in the IL, since they coordinate to the PEO chains. This was identified as the mechanism of a transition of the mesostructures, with increasing Li-salt content changing from a hexagonal to a lamellar and further to a micellar phase. In summary, both, the amount of IL and its compatibility with the PEO block, the latter being controlled by the Li-salt amount, influence the compositions of the formed mesophases and the ion diffusion in their liquid regions.

Influence factors analysis on the formation of silk I structure

Regenerated silk fibroin aqueous solution was used to study the crystalline structure of Bombyx mori silk fibroin in vitro. By controlling environmental conditions and concentration of silk fibroin solution, it provided a means for the direct preparing silk I structure and understanding the details of silk fibroin molecules interactions in formation process. In this study, silk fibroin molecules were assembled to form random coil at low concentration of solution and then, as the concentration increases, were converted to silk I at 55% relative humidity (RH). At the same time, the structure of silk fibroin forming below 45°C was mostly in silk I. A partial ternary phase diagram of temperature–humidity–concentration was constructed based on the results. The results showed silk I structure could be controlled by adjusting the external environmental conditions. The enhanced control over silk I structure, as embodied in phase diagram, could potentially be utilized to understand the molecular chain conformation of silk I in further research work.

Influence of Solution Parameters on Phase Diagram of Recombinant Spider Silk-Like Block Copolymers

Spider silks form interesting protein-based materials with exceptional mechanical properties from processing in aqueous systems. To more fully understand the role of specific chemical domains in the proteins responsible for these material features, selective regions are utilized to assess structure–function relationships. Toward this goal, the amphiphilic spider silk-like block copolymer HBA6 [hexahistidine tag (H), with hydrophilic (B) and hydrophobic (A) blocks] is studied to generate a partial phase diagram of the morphologies formed under different processing environments. Particles of HBA6 are prepared from a 2 m phosphate buffer at pH 5 and 8, and the resultant phase behavior upon ammonium sulfate (AS) addition is examined at room temperature for protein concentrations from 0.1 to 17 wt%. There is no apparent difference in the sizes of the microspheres formed at pH 8, irrespective of the amount of AS. In contrast, mixed morphologies ranging from unordered structures to clustered sheets to nanofibril-like morphologies are obtained at pH 5 with varying concentrations of AS. A partial ternary phase diagram is reported, representing the different morphologies obtained by changing the concentrations of HBA6, AS, and water. Differences in the morphologies as observed from scanning electron microscopy (SEM) are the result of altered protein-solute, interprotein, and intraprotein interactions caused by changing the pH and AS concentrations. The characteristics of the different morphologies illustrate how material properties based on motifs from spider silks can be tuned towards specific features, an important control point for matching materials to applications.

Phase diagram of tetradecyltrimethylammonium bromide (TTAB) + water + octanol system with application of mechanical deformation

Morphological properties of tetradecyltrimethylammonium bromide (TTAB)+water+octanol system in different concentrations have been studied. In the process, isotropic phase (L1) and nematic calamitic (NC), nematic discotic (ND), hexagonal E and lamellar D anizotropic mesophases have been determined by polarizing microscopy method and partial ternary phase diagram of the system set up. Textural properties of the anisotropic mesophases of the system have been discussed and their birefringence values measured. Mechanical deformation has been applied to the mesophases. The textural properties and the birefringence values have been observed to be changed by the deformation, after and before which changes have been compared.

Phase Behavior of Microemulsions Formulated with Sodium Alkyl Polypropylene Oxide Sulfate and a Cationic Hydrotrope

The partial ternary phase diagram of anionic extended surfactant of alkyl polypropylene oxide sulfate C12(PO)4SO4 alone and combined with the cationic hydrotrope, tetrabutyl ammonium bromide with water and decane were determined under ambient conditions. Middle phase microemulsion was formulated using salinity scans in the dilute region of surfactant/brine/decane. Visual inspection as well as cross polarizer and optical microscopy were used to detect anisotropy. Spinning drop tensiometer was used to measure interfacial tension (IFT). The first ternary phase diagram using the extended surfactant alone showed three one phase regions, the anisotropic lamellar liquid crystalline phase, L α and the isotropic L1 micellar liquid and L3 sponge phase. In the second ternary phase diagram using the extended surfactant combined with tetra butyl ammonium bromide, an isotropic micellar region, L 1, appeared in the diluted area of the phase diagram. Meanwhile the L α phase disappeared completely and the three phase region has a bluish transparent middle phase. Interfacial tension measurements between middle phase and brine, and between decane and brine yielded ultra low values. Calculated IFT values using the characteristic length obtained using De Gennes approximation gave almost half the measured values. The interfacial rigidity was also calculated and compared to values obtained from the literature.

SYNTHESIS AND PHASE ANALYSIS OF A NEW FERROELECTRIC (K0.5Na0.5)NbO3–Bi0.5K0.5TiO3–BaTiO3 TERNARY SOLID SOLUTION

In order to develop new lead-free pieozoelectric/ferroelectric materials, the y( K0.5Na0.5 ) NbO3 – (1 - y)[(1 - x) Bi0.5K0.5TiO3 – x BaTiO3 ] solid solution system is synthesized and the partial ternary phase diagram in the KNN-rich region with compositions of y = 0.98 to y = 0.96 is established. All the compositions studied show a gradual phase change from a tetragonal to an orthorhombic structure as the BT component increases. A mixture of tetragonal and orthorhombic phases is found in the composition range of x = 0.25 to 0.60 and y = 0.97, and x = 0.50 to 0.75 and y = 0.96, indicating a ternary morphotropic phase boundary region. The piezoelectric and ferroelectric properties of the 0.97(KNN)–0.03[0.60BKT–0.40BT] ceramics are characterized. The increase in remnant polarization as compared with pure KNN shows improved ferroelectricity by forming the ternary solid solution.

Viscoelastic Wormlike Micelles in Mixed Nonionic Fluorocarbon Surfactants and Structural Transition Induced by Oils

Formation and rheological behavior of viscoelastic wormlike micelles in an aqueous solution of a mixed system of nonionic fluorocarbon surfactants, perfluoroalkyl sulfonamide ethoxylate, C8F17SO2N(C3H7)(CH2CH2O)nH (abbreviated as C8F17EOn, n=20 and 3), was studied. A partial ternary phase diagram of water/C8F17EO20/C8F17EO3 was constructed at 25 degrees C by visual inspection through crossed polarizers. In the water/surfactant binary system, C8F17EO20 forms an isotropic micellar solution over a wide concentration range (approximately 80 wt %). The micellar solution of the C8F17EO20 can solubilize a significant amount of C8F17EO3, and the solubility increases with increasing C8F17EO20 concentration. With successive addition of C8F17EO3 to the aqueous C8F17EO20 solution, viscosity increases rapidly, and a viscoelastic solution is formed. The viscosity of the viscous sample was approximately 5th order of magnitude of pure water. The viscoelastic solution follows the Maxwell model typical of wormlike micelles at low-frequency region. With further addition of C8F17EO3 the viscosity decreases, and phase separation occurs. Addition of perfluoropolyether oil, (C3F6O)nCOOH, to the viscoelastic solution decreases the viscosity monotonically until phase separation. On the other hand, when perfluorodecalin oil, C10F18, is added, viscosity first decreases and attains a limiting value before excess oil phase separates out. The viscosity decrease in water/surfactant/oil systems is possibly caused by the microstructural transition in the network structure. Small-angle X-ray scattering (SAXS) measurements were performed to complement the rheological data. It has been found that the C8F17EO3 induces one-dimensional growth to the C8F17EO20 micelles. On the other hand, when (C3F6O)nCOOH is added, wormlike-sphere type transition is more likely to occur.

Phase Equilibria in DOPC/DPPC-d62/Cholesterol Mixtures

There is broad interest in the question of fluid-fluid phase coexistence in membranes, in particular, whether evidence for liquid-disordered (ld)-liquid-ordered (lo) two-phase regions or membrane “rafts” can be found in natural membranes. In model membrane systems, such phase behavior is observed, and we have used deuterium nuclear magnetic resonance spectroscopy to map the phase boundaries of ternary mixtures containing 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), chain-perdeuterated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC-d62), and cholesterol. For both this ternary model system and the binary DPPC-d62/cholesterol sytem, we present clear evidence for ld-lo two-phase coexistence. We have selected sample compositions to focus on this region of fluid-fluid phase coexistence and to determine its temperature and composition ranges. The deuterium nuclear magnetic resonance spectra for compositions near the ld-lo phase boundary at high cholesterol concentrations show evidence of exchange broadening or critical fluctuations in composition, similar to that reported by Vist and Davis. There appears to be a line of critical compositions ranging from 48°C for a DOPC/DPPC-d62/cholesterol composition of 0:75:25, to ∼−8°C for the composition 57:14:29. At temperatures below this two-phase region, there is a region of three-phase coexistence (ld-lo-gel). These results are collected and presented in terms of a partial ternary phase diagram that is consistent with previously reported results of Vist and Davis.

Polymerizable Bis(2-ethylhexyl)sulfosuccinate: Application in Microemulsion Polymerization

A hygroscopic and polymerizable salt ([2-methacryloyloxy]ethyl trimethylammonium chloride) is used to ion exchange the sodium ion in AOT (bis[2-ethylhexyl]sulfosuccinate, sodium salt) to produce a polymerizable form of AOT, MDOS ([2-methacryloyloxy]ethyl trimethylammonium bis[2-ethylhexyl]sulfosuccinate). A partial ternary phase diagram of water, MDOS, and methyl methacrylate (MMA) was determined at room temperature (22 +/- 1 degrees C). A relatively large L2 domain is obtained, but this domain is smaller than that obtained with AOT. Microemulsion polymerization in this domain at 70 degrees C, using AIBN (azoisobutyronitrile) as an initiator, produces an optically clear copolymer solid domain nearly as large as the L2 domain. This interesting behavior contrasts with similar studies of Pavel and Mackay [Langmuir 2000, 16, 8528] using a polymerizable surfactant DDAMA (didecyldimethylammonium methacrylate) that produced a much larger L2 domain than MDOS but yielded a much smaller optically clear domain after thermally initiated polymerization. Thermogravimetric analysis indicates that optically clear composites obtained at an MDOS/MMA weight ratio of 1:4 and containing 5% water (w/w; weight % water in microemulsion) released the water in a transition commencing around 160 degrees C and continuing to 250 degrees C. Thereafter, the thermal decomposition was substantially impeded relative to poly(methyl methacrylate) as a control, which was due to the fire-resistant nature of the MDOS monomer. Molecular weight measurements indicate MDOS/MMA copolymers form substantially higher molecular weights as the proportion of MDOS increases. At a given radius of gyration, higher MDOS-containing copolymers exhibit higher molecular weights, suggesting a more compact structure with increasing MDOS.

Preparation and characterization of nanosized hydroxyapatite particles in AOT inverse microemulsion

Nanosized particles of hydroxyapatite (HAP) were synthesized by reacting Ca (H2 PO4)2· H2 0 solution complex with equimolar Ca(OH)2 saturated solution in sodium bis (2-ethylhexyl) sulfosuccinate (AOT)/isooctane water-in-oil microemulsion. The formation of microemulsion strongly depended on water content w (w = [H2O]/[AOT] molar ratio) and concentration of surfactant and cosurfactant (1-octanol). By the variety of conductivity with w and the partial ternary phase diagram derived from a series of demarcation points, we set the basic component of microemulsions: [AOT] = 0. 1 M(mol/ dm3), [1-octanol] = 0.1 M and w = 3–9. Dynamic light scattering (DLS), UV-visible absorbance, TEM analysis and X-ray diffraction were used to characterize the microemulsion, formation of particles and resulting HAP particles. At low water content (w < 9), the water pool radius of the droplet in the Ca(H2 PO4)2 · H2O microemulsion lineally depended on w. The size of final HAP particles was strongly affected by water content w and reactant concentration. With increasing water content w from 3 to 9, the size of HAP particles increased from 10–20 nm to 40–50 nm at reactant concentration [Ca(H2 PO4) 2 · H2 0] = 12 × 10-3 mol/ dm3. The resulting HAP particles were poorly crystallized and spherical in morphology.

Phase behavior and hydration of silk fibroin.

The osmotic stress method was applied to study the thermodynamics of supramolecular self-assembly phenomena in crystallizable segments of Bombyx mori silkworm silk fibroin. By controlling compositions and phases of silk fibroin solution, the method provided a means for the direct investigation of microscopic and thermodynamic details of these intermolecular interactions in aqueous media. It is apparent that as osmotic pressure increases, silk fibroin molecules are crowded together to form silk I structure and then with further increase in osmotic pressure become an antiparallel beta-sheet structure, silk II. A partial ternary phase diagram of water-silk fibroin-LiBr was constructed based on the results. The results provide quantitative evidence that the silk I structure must contain water of hydration. The enhanced control over structure and phase behavior using osmotic stress, as embodied in the phase diagram, could potentially be utilized to design a new route for water-based wet spinning of regenerated silk fibroin.

Polymerization of lyotropic phases: 1. Isotropic fluid phase of two new polymerizable amphiphiles

We synthesized two new polymerizable amphiphiles. The partial ternary phase diagram of one of them was determined at 25°C. Homogeneous isotropic fluid phases formed by ternary systems of the two amphiphiles, respectively, were photopolymerized to form solid polymers with very small pores left by water. The appearance and morphology of the polymers was examined and correlated to the molecular structures and formulations.

Microstructure and room temperature deformation of Nb ss/Nb 5Si 3 in situ composites alloyed with Mo

Room temperature deformation behavior of Nb 5Si 3 based intermetallics in the ternary Nb–Si–Mo alloy system is investigated by compression testing in relation to microstructure and compositional effect. The partial ternary phase diagram of the Nb-Si-Mo alloy system containing phase equilibrium information at 1973 K is determined by metallography, X-ray diffraction and scanning electron microscopy (SEM) equipped with wavelength-dispersive X-ray fluorescence spectroscopy (WDS). A pseudo-binary compound of Nb 5Si 3–Mo 5Si 3 is confirmed to form at Nb 5Si 3-rich compositions by Mo addition, without having a solubility range of Si. The phase transformation from α-Nb 5Si 3 to β-Nb 5Si 3 is found to occur at about 5 at.% of Mo content on the Nb 5Si 3–Mo 5Si 3 pseudo-binary line. The observed yield stresses are largely dependent on not only the volume fraction and morphology of constituent phases but also the strength of Nb 5Si 3 phase equilibrating with Nb solid solution. The in situ composites consisting of α-Nb 5Si 3 phase and bcc solid solution exhibit higher yield stress than those consisting of β-Nb 5Si 3 phase and bcc solid solution when yield stress is compared at the same volume fraction of bcc phase. It is suggested that room temperature deformability of β-Nb 5Si 3 is superior to that of α-Nb 5Si 3 phase. Room temperature deformation behavior of the present composites will be discussed in relation to microstructural evolution.

Morphological Phase Diagram for a Ternary System of Block Copolymer PS310-b-PAA52/Dioxane/H2O

The partial ternary phase diagram was investigated for the polystyrene310-block-poly(acrylic acid)52 copolymer in dioxane/water mixtures in regions in which self-assembled nanoaggregates of various morphologies are seen. Both fractionated and unfractionated copolymers were used; the unfractionated copolymer contains homopolystyrene. The study was carried out over the range of water contents from 0 to 45 wt % and copolymer concentrations from 0.1 to 10 wt %. Freeze-drying transmission electron microscopy (TEM), turbidity measurements, as well as static and dynamic light scattering were employed. Because of the proximity of the melting points and boiling points of water and dioxane, quenching and subsequent freeze-drying of solution samples can be employed to preserve aggregate morphologies. The morphologies can then be observed using TEM. The reversibility of various morphological transitions was examined by means of TEM and turbidity measurements. With increasing water content, the sequence of copolymer structures in solution follows the order of single chains, spheres, sphere and rod mixtures, rods, rod and vesicle mixtures, and finally pure vesicles. The morphologies observed here are under thermodynamic control. Not only the water content but also the polymer concentration affects the morphologies and the sizes of the aggregates. For the unfractionated polymer, the single-chain/sphere boundary shifts to lower water contents relative to that of the fractionated copolymer, while the other morphological boundaries move to higher water contents. On the basis of the progressive changes of the aggregate morphologies with the addition of water, possible pathways of the morphological transitions are suggested and discussed briefly. Also, approximate thermodynamic functions are estimated for the morphological transitions on the basis of the morphological boundaries. The combination of freeze-drying TEM techniques with turbidity measurements is very useful in exploring the morphological behavior of block copolymers in solution.

Aggregate Structure, Gelling, and Coacervation within the L1 Phase of the Quasi-ternary System Alkyltrimethylammonium Bromide-Sodium Desoxycholate-Water

The phase behavior of mixtures of a cationic surfactant, cetyltrimethylammonium bromide (CTAB), with a bile salt, sodium desoxycholate (NaDOC), in water has been studied at 25°C. Mixing of the two surfactants at equimolar composition gave an associative type of phase separation similar to that observed in mixed polyelectrolyte surfactant systems. A partial ternary phase diagram was obtained in the water-rich corner and the limits of the two-phase (2L1) region were determined. The structural properties of the mixed bile salt-CTAB aggregates and their connection with phase separation were investigated by the application of dynamic light scattering (DLS) complemented with cryo-transmission electron microscopy (TEM) studies in the L1 phase surrounding the two-phase island and the gel region. In dilute concentrations both DLS and cryo-TEM techniques provide evidence for the presence of flexible cylindrical micelles at above mole fraction of NaDOC of 0.2. A progressive change in the appearance of the mixed micelles is directly visualized from cryo-TEM studies. At a mole fraction of 0.2 and below, small globular micelles exist; above mole fraction 0.3, flexible cylindrical thread-like micelles are found. A further increase in NaDOC gives structures with decreased extension and increased contortions, in many cases branching with Y-junctions. DLS autocorrelation decay curves have been analyzed using the REPES program which makes a smoothed inverse La-place transformation of the autocorrelation function. The hydrodynamic screening length evaluated using the Stokes-Einstein equation shows in a highly sensitive way the approach to the two-phase region. Critical dynamics behavior, i.e., an approach to a q3 -dependence of the average relaxation rate, is observed in the crossover region close to the coacervation boundary. DLS and rheology measurements were performed at higher concentrations, both in a region with gel-like composition and at several bile salt-CTAB mole fractions. The DLS and rheological properties observed are interpreted using concepts analogous to a solution of entangled polymers. The study was extended to include the influence of varied alkyl chain length and similar trends in aggregation and phase separation were observed when CTAB was replaced by other alkyltrimethylammonium bromides (C18TAB, C14TAB, and C12TAB).

Phase stability and microstructure of Al-Ti-Fe near Al3Ti

The phase stability and microstructure of Al-Ti-Fe near Al3Ti at 800 °C are studied by using high resolution electron microscopy and backscattered electron imaging. One of the most significant changes resulting from the addition of small amounts of iron in this system is to convert tetragonal Al3Ti or Al2Ti into cubic Ll2 structures. In addition, the added iron can change the stacking structure of Al2Ti and the domain size of the long-period one-dimensional antiphase domain structures. A partial ternary phase diagram in this region is also determined.

Solute effects on the colloidal and phase behavior of lipid bilayer membranes: ethanol-dipalmitoylphosphatidylcholine mixtures

By means of the scanning differential calorimetry, x-ray diffractometry, and the dynamic light scattering, we have systematically studied the phase and packing properties of dipalmitoylphosphatidylcholine vesicles or multibilayers in the presence of ethanol. We have also determined the partial ternary phase diagram of such dipalmitoylphosphatidylcholine/water/ethanol mixtures. The directly measured variability of the structural bilayer parameters implies that ethanol binding to the phospholipid bilayers increases the lateral as well as the transverse repulsion between the lipid molecules. This enlarges the hydrocarbon tilt (by up to 23 degrees) and molecular area (by < or = 40%). Ethanol-phospholid association also broadens the interface and, thus, promotes lipid headgroup solvation. This results in excessive swelling (by 130%) of the phosphatidylcholine bilayers in aqueous ethanol solutions. Lateral bilayer expansion, moreover, provokes a successive interdigitation of the hydrocarbon chains in the systems with bulk ethanol concentrations of 0.4-1.2 M. The hydrocarbon packing density as well as the propensity for the formation of lamellar gel phases simultaneously increase. The pretransition temperature of phosphatidylcholine bilayers is more sensitive to the addition of alcohol (initial shift: delta Tp = 22 degrees C/mol) than the subtransition temperature (delta Ts reversible 5 degrees C/mol), whereas the chain-melting phase transition temperature is even less affected (delta Tm = 1.8 degrees C/mol). After an initial decrease of 3 degrees for the bulk ethanol concentrations below 1.2 M, the Tm value increases by 2.5 degrees above this limiting concentration. The gel-phase phosphatidylcholine membranes below Tm are fully interdigitated above this limiting concentration. The chain tilt on the fringe of full chain interdigitation is zero and increases with higher ethanol concentrations. Above Tm, some of the lipid molecules are solubilized by the bound ethanol molecules. More highly concentrated ethanol solutions (> 7 M) solubilize the phosphatidylcholine bilayers with fluid chains fully and result in the formation of mixed lipid-alcohol micelles.