Strength of polymer phase boundaries with large interfacial width: Effects of interfacial profile and phase separation morphology

In this study, we investigate the effect of random copolymer additives on the interfacial profile, the lateral phase separation morphology, and the interfacial fracture toughness (G_c) between two immiscible polymers. The interface between polystyrene (PS)/poly(methyl methacrylate) (PMMA) was reinforced with a random copolymer mixture when two or more PS_f ‐r‐PMMA_1‐f random copolymers with different volume fraction, f, were blended. For short annealing time (<3 h), the random copolymer mixture exhibits a disordered and large domain structure (>1 lm) from which crazes can be extensively initiated and developed, leading to a large interfacial fracture energy. With increasing annealing time, the random copolymer mixture self‐organizes as multiple layers, with the composition that changes gradually from PS‐rich layers to PMMA‐rich layers across the interface, leading to a large interfacial width. However, within each layer, the random copolymer mixture microphase separates laterally into smaller domains (<200 nm). We found that the microphase‐separated domains with nanometer‐sized structure significantly affect the stability of craze fibrils that can be initiated and widened at the interface, leading to a decrease in the fracture energy. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1834–1846, 2010     

On phase equilibria,interfacial tension and phase growth in ternary polymer blends

A gradient squared free energy functional of the Landau-Ginzburg type is combined with Flory-Huggins theory to calculate minimum domain sizes, concentration profiles and interfacial tensions in ternary polymer blends. The dynamic equations governing spinodal decomposition are linearized to show that the minimum size for growth is identical to the thermodynamic minimum on phase volume. It is shown that unseparated, third components are enriched at the interface, reduce interfacial tension, increase stability and increase the minimum domain sizes. Enrichment of the third component at the interface causes concentrations at the major components to lie outside their binodal limits at a distance from the interface. Although the effects are most pronounced when the third component is a compatibilizer, the general phenomena remain true even when the third component is relatively incompatible. Generalizations to blends of N components are presented, and a robust method for calculating multicomponent phase diagrams is described.     

Charged micelle depletion attraction and interfacial colloidal phase behavior

Ensemble total internal reflection microscopy (TIRM) is used to directly measure the evolution of colloid-surface depletion attraction with increasing sodium dodecyl sulfate (SDS) concentration near the critical micelle concentration (CMC). Measured potentials are well described by a modified Asakura-Oosawa (AO) depletion potential in addition to electrostatic and van der Waals contributions. The modified AO potential includes effects of electrostatic interactions between micelles and surfaces via effective depletant dimensions in an excluded volume term and partitioning in an osmotic pressure term. Directly measured colloid-surface depletion potentials are used in Monte Carlo (MC) simulations to capture video microscopy (VM) measurements of micelle-mediated quasi-two-dimensional phase behavior including fluid, crystal, and gel microstructures. Our findings provide information to develop more rigorous and analytically simple models of depletion attraction in charged micellar systems.     

The interfacial tension and phase diagram of the Widom-Rowlinson mixture via Monte Carlo simulations

Results of Monte Carlo simulations are reported for the interfacial tension between two fluid phases in a binary mixture of penetrable spheres in which molecular pairs of like species do not interact, while those of unlike species interact as hard spheres. Semigrand canonical ensemble Monte Carlo simulations in a cubic cell with periodic boundary conditions are used to obtain histograms for various system sizes at various densities. At a given density, the interfacial tension and compositions of coexisting phases for an infinite system are evaluated via histogram analysis combined with finite-size scaling. The density dependence of the interfacial tension and phase diagram for an infinite system are thus obtained. The simulated behavior of the interfacial tension close to the critical density corroborates previous suggestions that the model belongs to the three-dimensional Ising universality class.     

Polyarylates. V. The influence of phase transfer agents on the interfacial polycondensation

The effect of various phase transfer agents on the interfacial polycondensation of bisphenol A with isophthaloyl chloride was investigated. It was found that the transfer rate of bisphenolate and, thus, the reaction rate of polycondensation were increased with an increasing lipophilicity of the phase transfer agent, i.e. TBAC > TEBAC > TEAC, whereas the equilibrium of bisphenolate between the organic phase and the aqueous phase was hardly affected. Moreover, experimental evidence indicated that a phase transfer agent of high lipophilicity reduced the hydrolysis of the acid chloride, an important aspect in interfacial polycondensation.     

表面活性剂与油相动态界面张力影响因素研究

对不同类型表面活性剂烷基糖苷(APG1214)、咪唑啉(IAS)、十二烷基苯磺酸钠(SDBS)、烷基酚醚羧酸盐(ss-231)的油水动态界面张力进行了研究。在60℃,5 000 r·min-1条件下,考察了表面活性剂的浓度、表面活性剂的结构、正构烷烃碳数以及原油中活性物质对形成低界面张力影响。实验结果表明:表面活性剂亲水基的亲水性越强,亲水基之间排斥力越小,使得在油水界面排布的密度越大,降低界面张力的效果会更好;当表面活性剂疏水碳链与烷烃碳链相似时,降低界面张力的效果会更明显;无碱体系中原油中的活性物质可在油水界面上形成粘弹性界面膜,这种界面膜的形成减少了表面活性剂分子在界面的吸附,使界面张力升高。     

Temperature-responsive Pickering high internal phase emulsions for recyclable efficient interfacial biocatalysis

The field of biocatalysis is expanding owing to the increasing demand for efficient low-cost green chemical processes. However, a feasible strategy for achieving product separation, enzyme recovery, and high catalytic efficiency in biocatalysis remains elusive. Herein, we present thermoresponsive Pickering high internal phase emulsions (HIPEs) as controllable scaffolds for efficient biocatalysis; these HIPEs demonstrate a transition between emulsification and demulsification depending on temperature. Ultra-high-surface-area Pickering HIPEs were stabilized by Candida antarctica lipase B immobilized on starch particles modified with butyl glycidyl ether and glycidyl trimethyl ammonium chloride, thus simplifying the separation and reuse processes and significantly improving the catalytic efficiency. In addition, the switching temperature can be precisely tuned by adjusting the degree of substitution of the modified starches to meet the temperature demands of various enzymes. We believe that this system provides a green platform for various interfacial biocatalytic processes of industrial interest.

The thermoresponsive Pickering high internal phase emulsions stabilized by starch particles as controllable scaffolds for efficient biocatalysis, which simplified the separation and reuse processes and significantly improved the catalytic efficiency.     

The interfacial enhancement of LLDPE/whisker composites via interfacial crystallization

Interfacial interaction plays a key role in the preparation of high performance polymer composites. In this work, in order to explore the possibility to enhance the interfacial interaction via interfacial crystallization of polymer matrix onto the filler surface, interfacial crystallization structure and mechanical properties of linear low density polyethylene (LLDPE)/whisker composites were investigated. The composites were firstly prepared by melt compounding, followed by processing in both traditional and dynamic injection molding. DSC, WAXD, SEM were used to characterize the interfacial crystallization structure. And the mechanical properties were measured by tensile testing. An imperfect shish‐calabash structure, with whisker served as shish, and irregular LLDPE spherulite as imperfect calabash, was formed during common injection molding processing. Such a structure was considered as the main reason for the strong interfacial adhesion and the obviously improved tensile strength and modulus. Furthermore, introducing shear could cause the formation of relatively perfect shish‐calabash structure, leading to the stronger interfacial adhesion. Copyright © 2011 John Wiley & Sons, Ltd.     

Gas-liquid phase separation in oppositely charged colloids: stability and interfacial tension

We study the phase behavior and the interfacial tension of the screened Coulomb (Yukawa) restricted primitive model (YRPM) of oppositely charged hard spheres with diameter sigma using Monte Carlo simulations. We determine the gas-liquid and gas-solid phase transitions using free energy calculations and grand-canonical Monte Carlo simulations for varying inverse Debye screening length kappa. We find that the gas-liquid phase separation is stable for kappasigma相似文献   

Effects of ion solvation on phase equilibrium and interfacial tension of liquid mixtures

We study the bulk thermodynamics and interfacial properties of electrolyte solution mixtures by accounting for electrostatic interaction, ion solvation, and inhomogeneity in the dielectric medium in the mean-field framework. Difference in the solvation energy between the cations and anions is shown to give rise to local charge separation near the interface, and a finite Galvani potential between two coexisting solutions. The ion solvation affects the phase equilibrium of the solvent mixture, depending on the dielectric constants of the solvents, reflecting the competition between the solvation energy and translation entropy of the ions. Miscibility is decreased if both solvents have low dielectric constants and is enhanced if both solvents have high dielectric constant. At the mean-field level, the ion distribution near the interface is determined by two competing effects: accumulation in the electrostatic double layer and depletion in a diffuse interface. The interfacial tension shows a nonmonotonic dependence on the salt concentration: it increases linearly with the salt concentration at higher concentrations and decreases approximately as the square root of the salt concentration for dilute solutions, reaching a minimum near 1 mM. We also find that, for a fixed cation type, the interfacial tension decreases as the size of anion increases. These results offer qualitative explanations within one unified framework for the long-known concentration and ion size effects on the interfacial tension of electrolyte solutions.     

Synthesis of metal-containing carbohydrate polymers employing crown ether phase transfer catalyzed interfacial condensation

Phase transfer catalyzed interfacial reaction of the polysaccharide dextran (C₆H₁₀O₅)_n with organotitanium and organotin dichlorides to form metal-containing carbohydrate polymers has been carried out in the presence of two bases, sodium hydroxide and triethylamine. Interfacial systems employing sodium hydroxide with a crown ether phase transfer catalyst (PTC) gave generally greater yields compared with the analogous systems without a PTC. The trend of maximum yield for triethylamine systems with organotin dichloride not containing a PTC was different from that observed for the sodium hydroxide systems without a PTC, probably because of the ability of triethylamine to act as a PTC.     

Thermotropic and lyotropic phase properties of glycolipid diastereomers: role of headgroup and interfacial interactions in determining phase behaviour

Recent advances in the area of glycobiology have been paralleled by progress in our understanding of the physical properties of glycoglycerolipids (GGLs). These advances have been accelerated by interest in the new found roles of these simple glycolipids in nature, by advances in synthetic procedures, and by an interest in the technological application of a group of amphiphiles with unique physical and chemical properties. Here, we consider the phase properties of some GGL/water systems containing either a single hexopyranoside or pentopyranoside headgroup. Recent calorimetric and X-ray diffraction measurements of some GGL diastereomers suggest that both headgroup and interfacial hydration play a major role in determining both lyotropism and mesomorphic phase properties as the chemical structure of the lipid headgroup, interface and hydrocarbon chains are systematically altered. For GGLs of a given chain length, interactions between the headgroup/interface and water determine whether or not a highly ordered, lamellar crystalline phase is formed, the number of such phases and their rate of formation and, in some cases, the nature of the molecular packing of those phases. In the liquid crystalline phases, the hydrocarbon chains determine the area per molecule in the lamellar liquid crystalline phase, but it is the cross-sectional area of the hydrated headgroup and the penetration of water into the interface which determines the nature of the non-lamellar phases, probably through small changes in interfacial geometry as the lateral stresses in the headgroup region increase.     

Phasepy: A Python based framework for fluid phase equilibria and interfacial properties computation

Phasepy is a Python based package for fluid phase equilibria and interfacial properties calculation from equation of state (EoS). Phasepy uses several tools (i.e., NumPy, SciPy, Pandas, Matplotlib) allowing use Phasepy under Jupyter Notebooks. Phasepy models phase equilibria with the traditional ϕ –γ and ϕ –ϕ approaches, where ϕ (fugacity coefficient) can be modeled as a perfect gas, virial gas or EoS fluid, whereas γ (activity coefficient) can be described by conventional models (NRTL, Wilson, Redlich-Kister expansion, and the group contribution modified-UNIFAC). Interfacial properties are based on the square gradient theory couple to ϕ –ϕ approach. The available EoSs are the cubic EoS family extended to mixtures through the quadratic, modified-Huron-Vidal, and Wong-Sandler mixing rules. Phasepy allows to analyze phase stability, compute phase equilibria, interfacial properties, and optimize their parameters for vapor–liquid, liquid–liquid, and vapor–liquid–liquid equilibria for multicomponent mixtures. Phasepy implementation, and robustness are illustrated for binary and ternary mixtures.     

Microemulsification of triglyceride sebum and the role of interfacial structure on bicontinuous phase behavior

A unique triblock surfactant is reported that allows for the efficient microemulsification of triglycerides. Unlike the results of all previous efforts, these triglyceride microemulsions can be formed without the use of cosurfactants or dilution with co-oils and follow the classical patterns of surfactant phase behavior exhibited by mixtures of water, alkane oils, and nonionic oligoethylene glycol surfactants, i.e., progression from oil/water emulsions to one-phase microemulsions to water/oil emulsions with increasing temperature. Lamellar phases that usually dominate the aqueous phase behavior of surfactant/triglyceride mixtures are suppressed, allowing for the formation of single-phase microemulsions containing equal amounts of triglyceride and water. These isotropic and low-viscous fluids are particularly useful for cleansing and delivery of functional ingredients in skin care products. The effects of mixing a variety of typical skin care ingredients and components of sebum (skin oil) were also explored. Fatty acids significantly reduce the average microemulsion temperature, while other ingredients and oils, which do not partition at the oil/water interface, have less impact on the phase behavior. In all cases, one-phase microemulsions containing equal amounts of oil and water can be formed even at high additive concentrations. Indeed, partial replacement oftriglyceride with any of the additives examined consistently reduced the amount of surfactant necessary to form single-phase microemulsions. However, the greatest boost in surfactant efficiency was found with the addition of medium molecular weight amphiphilic block copolymers.     

Analysis of conducting-system frequency response data for an interfacial amorphous phase of copper-core oxide-shell nanocomposites

Complex electrical-conductivity experimental data sets for the interfacial amorphous phase in copper-core-copper-oxide-shell nanostructured composites have been analyzed using two Kohlrausch-related frequency response models recently developed for analysis of the dispersive electrical response of conductive materials. Such analysis has been carried out for both the precursor (herein referred to as the reference) glass as well as the glass in which the core-shell nanostructure was developed after suitable heat treatment. Complex nonlinear-least-squares data fitting at each temperature employed composite Kohlrausch models that included electrode effects. Because of the lack of sufficient high-frequency data, it was necessary to use fixed, rather than free, values of the shape parameter beta1 of the model. On the basis of topological considerations, its values were set at 13 and 23 for the reference glass and the core-shell structured glass, respectively. The activation energies of resistivity for the reference and the treated glasses were found to have values of about 2 and 0.4 eV, respectively, indicating two different mechanisms of electrical conduction. A blocking-electrode measurement on the reference glass indicated the presence of an electronic as well as an ionic component of the electrical conductivity, with the ionic part dominating at the temperatures for which the present analyses were carried out.     

Structural morphology developments in the interfacial phase of heterocoagulated composite particles: dynamic mechanical measurements

The dynamic mechanical properties of polymeric composites composed of poly (methyl methacrylate) continuous-phase and various inclusion types of heterocoagulated composite particles were investigated in order to relate them to the morphology of shell region of composite particles. Using the heterocoagulation process, large particles were encapsulated with various types of small particles: (1) conventional linear-type polymer particles; (2) crosslinked polymer particles; and (3) reactive polymer particles capable of forming crosslinked structure, whereby the interfacial properties of the composite become modified. These composite particles were subsequently annealed to form continuous shell regions and then mixed with matrix particles. It is shown that chain diffusion movement of the small particles having different chain characteristics influences the network formation at the interfacial shell region. The ability of maintaining interfacial domain structure depends on the degree of network formation.     

Structural stabilization of phase separating PC/polyester blends through interfacial modification by transesterification reaction

Competition between phase separation and transesterification in immiscible polymer blends of polycarbonate (PC) and a copolyester (PET) is studied as a function of time and temperature by differential scanning calorimetry (DSC) and small-angle neutron scattering (SANS). We found that (1) Global structure coarsens at T ≤ 200°C due to the dominance of phase separation over transesterification and melts at T ≤ 220°C due to the dominance of transesterification at the domain interface. However, transesterification is slow but still significant even at T ≤ 200°C. (2) An intricate balance of transesterification and phase separation rates controls global and interfacial structures. (3) Interfacial structures become measurable under certain conditions, and the interfacial thickness between PC or PET and the copolymers generated by transesterification increases with time. (4) DSC results are consistent with results obtained by SANS, but the latter is more sensitive than the former and differentiates the structural change at different length scales caused by phase separation and transesterification. © 1994 John Wiley & Sons, Inc.     

Salt-tuned phase separation of poly(S-co-Nipam) core-shell particles via interfacial in situ polymerization

In this study, temperature-sensitive amphiphilic core-shell nanoparticles of N-isopropylacrylamide (NIPAM) were prepared via interfacial in situ polymerization of styrene (S) and NIPAM. Oil soluble cumene hydroperoxide (CHPO) oxidizer and water soluble reductant iron(II) sulfate (FS), polyurethane and hexadecane were used as interfacial initiation pair, surfactant and co-stabilizer, respectively. Radicals are produced and initiate polymerization only when the CHPO and FS are present at oil/water interface. FT-IR and ¹H NMR spectroscopy confirmed the co-polymerization of these monomers. The core-shell structure with a diameter 150 nm was corroborated by TEM and FESEM. DSC analysis showed the existence of two glassytransition temperatures of the resulting particles. Salt-tuned phase separation behavior of poly(S-co-NIPAM) core-shell particles has been studied by dynamic light scattering. The lower critical solution temperature of the core-shell particles decreased linearly as a function of NaCl concentration that was attributed to the “salt out effect”. The variation of particle diameter showed a sigmoidal plot as a function of temperature regardless of the salt concentration.     

Evolution of phase dimensions and interfacial morphology of polypropylene/polystyrene compatibilized blends during mixing

The morphology development of polypropylene/polystyrene (PP/PS) blends was studied by means of effective mathematics methods. Time resolved fracture morphology measurements on PP/PS (20/80) blends compatibilized with styrene-butadiene-styrene block copolymer (SBS) suggested that PP/SBS domains acted as a warehouse supplying compatibilizer (SBS) to the phase boundary in the initial stage of mixing and promoted the formation and development of the transition layer. The development of the transition layer leaded to a more complicated morphology of fracture surface and strengthened the adhesion between phases, which was quantitatively investigated using Brown fractal dimension D_Brown. In the early stage of the mixing (<2.0 min), the mean chord length Λ_m used to describe the domain size decreased; simultaneously, the distribution of Λ trended to uniform as the mixing proceeded. After 2.0 min, Λ_m fluctuated in a definite range. Further, a normalized distribution of dimensionless domain sizes Λ/Λ_m was independent of mixing time, indicating that the late stage of phase dispersion can be scaled with a time-depended single length parameter Λ_m. In other words, the morphology development shows a possible dynamic scaling behavior.     

Incomplete phase inversion W/O/W emulsion and formation mechanism from an interfacial perspective

Water-in-oil-in-water (W/O/W) double emulsion can be prepared by incomplete phase inversion method using both medium chain triglycerides (MCT) and isopropyl myristate (IPM) as oil phase, Span 85-Tween 80 (HLB values of 2.5-3.0) as mixed emulsifiers. The preparation method was simple, and the final double emulsions were proved of good microstructure and particle size distribution. Owning to the addition of Tween 80 to Span 85, interfacial tension, interfacial viscosity and modulus decreased, which contributed to the phase inversion. Furthermore, formation of reverse micelles under high-speed dispersion may be a hypothesis to explain the incomplete phase inversion phenomenon.