Compatibilization Of Polymer Blends Research Articles

Synthesis and characterization of amphiphilic methoxypoly(ethylene glycol)-polystyrene diblock copolymer by ATRP and NMRP techniques

Amphiphilic block copolymers are used in a variety of applications, for example, as stabilizers for emulsions and dispersions or as compatibilizers in polymer blends. Amphiphilic diblock copolymer composed of methoxypoly(ethylene glycol) and polystyrene (MPEG-b-PS) was synthesized using atom transfer radical polymerization (ATRP) and nitroxide-mediated radical polymerization (NMRP). In order to synthesize MPEG-b-PS diblock copolymer using ATRP, monofunctional MPEG macroinitiator (chloroacetylated MPEG [MPEG-Cl]) was prepared from monohydroxyfunctional poly(ethylene glycol) and initiated end group on the basis of chloroacetyl chloride. ATRP was carried out in bulk using MPEG-Cl as the macroinitiator, copper chloride (CuCl)/2,2′-bipyridine (bipy) as the catalyst ([MPEG-Cl]/[CuCl]/[bipy] = 1:1:3), and styrene as the monomer. For preparation of MPEG-b-PS by means of NMRP, firstly, 1-hydroxy-2,2,6,6-tetramethyl-piperidine (TEMPO-OH) was obtained by reduction of 2,2,6,6-tetramethyl-piperidinyl-1-oxy (TEMPO) with sodium ascorbat. Then, TEMPO-OH was coupled with chloroacetylated MPEG (MPEG-Cl) to yield the macroinitiator MPEG terminated with a TEMPO unit (MPEG-CO-TEMPO). At last, MPEG-CO-TEMPO was further used to prepare the diblock copolymer MPEG-b-PS by ‘living’ free radical polymerization of styrene. The products were purified and identified by Fourier transform infrared (FT-IR) spectroscopy, 1H nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC).

Preparation of Poly(acrylic acid)-Poly(ethylene oxide) Nanofibers via Electrospinning and Investigation of Their Morphology

Abstract The poly(acrylic acid)/poly(ethylene oxide) (PAA/PEO) blend nanofibers at 100/0, 80/20, 50/50, 20/80 and 0/100 weight ratios were obtained via electrospinning process. Intermolecular interactions, miscibility and compatibility of polymer blends were studied by Fourier transform infrared (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and UV-visible spectrophotometer. The results suggest that intermolecular interactions have occurred between pure PAA and PEO in PAA/PEO blend. These interactions made PAA/PEO blend miscible at above-mentioned weight ratios. Additionally, the morphology and the fibers diameter were investigated using scanning electron microscope (SEM) analysis, which indicated beadless fibers with diameter range of about 120 to 300 nm. It was observed that the homogenous nanofibers with the smaller diameter were obtained in PAA/PEO blend with PAA dominant content. Finally, SEM results suggest that the formation of pure PAA nanofibers with concentration of 5.0 wt.% would not occur. Whereas, in the same concentration, pure PEO and PAA/PEO blend nanofibers with no bead defects were obtained. However, in higher pure PAA concentrations electrospun fibers were formed.

Blend Microspheres of Poly(3-hydroxybutyrate) and Cellulose Acetate Phthalate for Colon Delivery of 5-Fluorouracil

Blend microspheres of poly(3-hydroxybutyrate) (PHB) and cellulose acetate phthalate (CAP) have been prepared in compositions of 2:1, 1:1, and 1:3 (w/w) by the solvent evaporation technique. These pH-sensitive polymers were utilized to investigate the colon delivery of 5-fluorouracil (5-FU), an anticancer drug. The surface morphology of the microspheres was studied by scanning electron microscopy (SEM), which confirmed their spherical nature with sizes ranging from 29 to 67 μm, as well as pore structures before and after the dissolution experiments. Fourier transform infrared (FTIR) spectroscopy was used to confirm the polymer blend compatibility and to confirm the absence of drug–polymer interactions. Differential scanning calorimetry (DSC) was employed to study the crystalline nature and molecular-level dispersion of 5-FU in the matrixes after encapsulation. In vitro release experiments were performed at 37 °C in simulated buffer medium of the stomach (pH 1.2) for 2 h, followed by simulated intestinal me...

Morphology and properties of nylon 6 and high density polyethylene blends in presence of nanoclay and PE‐g‐MA

AbstractIn this study, we report the synergistic effect of nanoclay and maleic anhydride grafted polyethylene (PE‐g‐MA) on the morphology and properties of (80/20 w/w) nylon 6/high density polyethylene (HDPE) blend. Polymer blend nanocomposites containing nanoclay with and without compatibilizer (PE‐g‐MA) were prepared by melt mixing, and their morphologies and structures were examined with scanning electron microscopy (SEM) and wide angle X‐ray diffractometer (WAXD) study. The size of phase‐separated domains decreased considerably with increasing content of nanoclay and PE‐g‐MA. WAXD study and transmission electron microscopy (TEM) revealed the presence of exfoliated clay platelets in nylon 6 matrix, as well as, at the interface of the (80/20 w/w) nylon 6/HDPE blend–clay nanocomposites. Addition of PE‐g‐MA in the blend–clay nanocomposites enhanced the exfoliation of clays in nylon 6 matrix and especially at the interface. Thus, exfoliated clay platelets in nylon 6 matrix effectively restricted the coalescence of dispersed HDPE domains while PE‐g‐MA improved the adhesion between the phases at the interface. The use of compatibilizer and nanoclay in polymer blends may lead to a high performance material which combines the advantages of compatibilized polymer blends and the merits of polymer nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Effect of Nanoclay and SEBS-g-MA on the Morphology and Properties of Immiscible Poly(methyl methacrylate)/Polystyrene Blend

In recent years, nanoclays are being used as compatibilizer for various immiscible polymer blends. However, little work has been done on the morphology of immiscible polymer blends in presence of both the nanoclay and a reactive compatibilizer. Here, we report the synergistic effect of nanoclay and SEBS-g-MA on the morphology and properties of (70/30 w/w) PMMA/PS blend. Scanning electron microscopy study of the blend with various amount of nanoclay and SEBS-g-MA indicated a reduction in the average domain sizes (D) of dispersed PS phase in PMMA matrix compared to that in the pure blend. Addition of both SEBS-g-MA and nanoclay significantly lowered the D of PS in the blend compared to that with only SEBS-g-MA or clay. X-ray diffraction study and transmission electron microscopy revealed the presence of intercalated clay platelets in PMMA matrix, as well as, at the interface of the (70/30 w/w) PMMA/PS blend-clay nanocomposites. Addition of SEBS-g-MA in the blend-clay nanocomposites promoted the exfoliation of clays in PMMA matrix. Thus, exfoliated clay platelets in PMMA matrix effectively restricted the coalescence of dispersed PS domains while SEBS-g-MA improved the adhesion between the phases at the interface. At certain loading (phr), storage modulus, elongation at break and thermal stability of the blend were greatly improved when both the nanoclay and SEBS-g-MA were present in the blend. The use of reactive compatibilizer and nanoclay in polymer blends may lead to a high performance material which combines the advantages of compatibilized polymer blends and the merits of polymer nanocomposites.

The use of functionalized nanoparticles as non‐specific compatibilizers for polymer blends

AbstractThe ability to form blends of polymers offers the opportunity of creating a new class of materials with enhanced properties. In addition to the polymer components, recent advances in nanoengineering have resulted in the development of nanosized inorganic particles that can be used to improve the properties of the blend, such as the flammability and the mechanical properties. While traditional methods using copolymer compatibilizers have been used to strengthen polymer blends, here, we show that the inorganic nanosized filler additive can also serve as a compatibilizer as it can localize to the interface between the polymers. We use experimental and theoretical studies to show the fundamental mechanisms by which inorganic fillers with large aspect ratio and at least one‐dimension in the nanometer range, can act as non‐specific compatibilizers for polymer blends. We examine a series of nanosized fillers, ranging from nanotubes to nanoclays (with varying aspect ratios) in a model polystyrene (PS)/poly(methylmethacyralate) (PMMA) blend. Using a number of experimental techniques such as transmission electron microscopy (TEM), scanning tunneling X‐ray microscopy (STXM), and atomic force microscopy (AFM) we postulate that the mechanism of compatibilization occurs as a result of the fillers forming in situ grafts with the immiscible polymers. We also use theoretical studies to show that the aspect ratio and the bending energy of the fillers play a key role in the compatibilization process. Our results indicate that the compatibilization is a general phenomenon, which should occur with all large aspect ratio nanofiller additives to polymer blends. Copyright © 2010 John Wiley & Sons, Ltd.

A study on compatibility of polymer blends of polystyrene/poly(4‐vinylpyridine)

AbstractBlends of polystyrene/poly (4‐vinylpyridine) have been prepared by casting from a common solvent. The compatibility of the blends was studied by using dilute solution viscometry (DSV), differential scanning calorimetery (DSC), Fourier transformation‐infrared spectroscopy (FT‐IR), and scanning electron microscopy (SEM). The relative viscosity versus composition plots for the blends are not perfect linear. The corresponding intrinsic viscosity values show negative deviation from ideal behavior when plotted against composition. Also, the modified Krigbaum and Wall interaction parameter, Δb, shows small and negative values for all compositions except for the blend PS/P4VP (25 : 75). The results indicate that the polymers are incompatible but small interaction values predict physically miscible blends which eventually show phase separation, as is observed in the present studies. However, the blends as obtained show a single, composition‐dependent, glass transition temperature that fits the Fox equation well, indicating the presence of homogeneous phase. The constant, k obtained from Gordon‐Taylor equation suggests intermolecular attraction between these polymers. FT‐IR and SEM support the results of DSV and DSC. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

The effect of interfacial properties on the deformation and relaxation behavior of PMMA/PS blends

This work aims at studying the role of interface properties on the rheological behavior of non-compatibilized and compatibilized polymer blends. Blends of polymethylmetacrylate (PMMA) with polystyrene (PS) and PS functionalized with oxazoline (PSOX) with concentrations of up to 20 w/w of the dispersed phase were used. It was observed that until a critical concentration is reached the increase in PSOX content leads to a significant increase in (a) the elasticity at low frequencies and (b) the relaxation time after cessation of flow, both in shear and extension. This points to a likely significant role played by interface elasticity. Since no chemical reactions occur between PMMA and the oxazoline groups of PSOX, the latter is probably caused by the partial miscibility between PMMA and PSOX. Beyond this critical concentration, the amount of PSOX does not have a significant influence on the rheological behavior of the blends. In order to gain an insight into the relaxation dynamics of the droplets and interface, and their relationship with the rheological behavior of the blends, small angle light scattering (SALS) was used in diluted blends (1 wt % of the dispersed phase) during step shear. SALS shows a slight deformation of dispersed phase in the vorticity direction for the 99PMMA/1PSOX blend while the droplets of the 99PMMA/1PS blend deforms in the flow direction only. This result confirms the large increase in the interfacial elasticity for the 99PMMA/1PSOX blend.

Real time assessment of the compatibilization of polypropylene/polyamide 6 blends during extrusion

The reactivity of maleic anhydride and acrylic acid polypropylene graft copolymers with amine groups and their effect in the compatibilization of polymer blends was analyzed in real time during the reactive processing of compatilized polypropylene/polyamide 6 (PP/PA6) blends. The presence of compatibilizers in the blend produces a block copolymer PP-PA6, which stays in the blends interface, lowering the interfacial tension and reducing the PA6 particle size, affecting the light extinction phenomena. The in-line optical detector is able to indirectly quantify the conversion of the compatibilization reaction of the blends. The signal intensity of the detector increases with the increase of the PA6 content due to the increase in the number of particles. Quantitative off-line FTIR analyses of the compatibilized blends have shown that the amount of block copolymer formed when polypropylene grafted with acrylic acid (PP-g-AA) is used as compatibilizer increases with its content in the blend. There is a good correlation between the in-line optical measurement and the off-line amidic bond content formed. Non-reacted compatibilizers are always present in the reactive blends whose content is proportional to its initial concentration. The PA6 particle size data obtained from scanning electron microscopy analysis showed good correlation with the in-line measurements. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers

Compatibilization of immiscible poly(vinyl chloride) (PVC)/polystyrene (PS) blends with maleic anhydride–styrene–vinyl acetate terpolymer (MAStVA)

In this study, compatibilizing effects of maleic anhydride–styrene–vinyl acetate (MAStVA) with various terpolymer ratios on immiscible blends of poly(vinyl chloride) (PVC) and polystyrene (PS) blends were investigated by viscometry method, thermo-mechanical analysis (TMA) and infrared spectroscopy (FTIR). The viscosimetric measurements were carried out for PVC, PS, a (70:30) blend of PVC/PS and a blend of PVC/PS/MAStVA containing 2–10% of the terpolymer in the range of concentrations (0.25–2.00 g dL −1) where tetrahydrofuran (THF) is the solvent. The interaction parameter (Δ b) was used to study the miscibility and compatibility of polymer blend in solution, obtained from the modified Krigbaum and Wall theory. TMA and FTIR measurements were also used to investigate the miscibility of this pair of polymers. In consequence of the study, it was observed that a considerable improvement was achieved in the miscibility of PVC/PS blends by adding among 4 and 10 wt.% of compatibilizer.

Reactive compatibilization of polymer blends by γ‐irradiation: Influence of the order of processing steps

AbstractResults concerning γ‐irradiation of polymer blends such as HDPE/ground tire rubber (GTR) and PP/HDPE are reported in this article with a special emphasis on the order of processing steps. Irradiation dose varied in the range 0–100 kGy. The two first polymers (HDPE and rubber) are preferentially crosslinked under γ irradiation while PP undergoes chain scission. Mechanical tests and differential scanning calorimetry (DSC) analysis show that the efficiency of the reactive compatibilization by γ irradiation depends greatly on the chronology of γ‐irradiation and injection‐molding steps. Electron spin resonance (ESR) results reveal that numerous radicals remain trapped in the materials after γ‐irradiation even after a long time. Then the effect of irradiation on material properties is different if polymers are melted after irradiation or not. Crosslinking and chain scission are not affected in an equivalent way by the order of processing steps. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

The effect of incorporation of POSS units on polymer blend compatibility

AbstractIn this work, the compatibility of poly(methyl methacrylate) (PMMA) and polystyrene (PS) polymers with their polyhedral oligomeric silsesquioxane (POSS) copolymers combined by solution blending is investigated, to determine the effect of incorporation of the POSS unit on polymer compatibility. The morphology of these tethered POSS copolymer/polymer blends was studied by electron microscopy, thermal analysis, and density. Although the basic PS/PMMA blend was clearly immiscible, it was also found that the incorporation of POSS into the PS chain led to incompatibility when the POSScoPS copolymer was blended with PS homopolymer. However, conversely, in the case where the POSS moiety was included as part of a copolymer with PMMA, the copolymer was miscible with the PMMA homopolymer. The presence of isobutyl units on the corners of POSS cage is clearly sufficient to encourage miscibility with PMMA. Interestingly, blends of the two different POSS copolymers led to an immiscible structure, despite having the common POSS units, the interactions between the POSS moieties clearly not being sufficient to drive compatibility. The POSS copolymers have also been used as interfacial agents in immiscible PS and PMMA blend, and it has been found that the appearance of the interface bonding is improved, although the phase morphology is only slightly changed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Role of Compatibilization in Polymer Nanocomposites

Abstract Polymeric nanocomposites based on nanoclay, nanosilica, carbon nanotubes, and ceramic or mineral nanoparticles have been developed for a variety of applications. The large surface-to-mass ratios of these particles require good adsorption of the polymeric material on the particle surface to provide the adhesion levels between the filler and matrix resin necessary for improved performance. We review the basic principles underlying these surface interactions and their application in the preparation of a variety of these nanocomposites, as well as in explaining their performance. We demonstrate that the principles underlying the compatibilization of polymer blends and alloys can be successfully used to design nanocomposites and understand their performance.

Preparation and characterization of biodegradable thermoplastic Elastomers (PLCA/PLGA blends)

A biodegradable elastomer (PLCA/PLGA blends) was prepared and characterized. First, poly(DL-lactide-co-e-caprolactone) (PLCA) and poly(DL-lactide-co-glycolide) (PLGA) were synthesized. Infrared (IR) spectroscopy, 1H nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC) were used to confirm the formation and structure of PLCA and PLGA. The solubility parameters of PLCA and PLGA were measured to estimate the miscibility between them. A series of PLCA/PLGA blends was prepared through solution blending. The morphology of all blends was examined by scanning electron microscope (SEM), and no obvious phase separation was detected at various ratios of PCLA and PLGA. Thermomechanical properties were characterized using thermogravimetry (TG), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA), the results showed that the PLCA/PLGA blends were a type of immiscible but compatible polymer blend. Mechanical properties, particularly stress-strain behavior, were examined; with an increase in PLGA content, the tensile strength and Young’s modulus of the blends increased dramatically, while elongation at break decreased.

Morphology and rheology of compatibilized polymer blends: Diblock compatibilizers vs crosslinked reactive compatibilizers

Reactive compatibilization is commonly used when blending immiscible homopolymers. The compatibilizers formed from the interfacial coupling of two types of reactive chains often have a graft copolymer architecture. Here we consider the case where both reactive chains are multifunctional, leading to a crosslinked copolymer at the interface. Experiments were conducted on a model blend of ∼30% polydimethylsiloxane drops in a polyisoprene matrix. Compatibilizer was formed by an interfacial reaction between amine-functional polydimethylsiloxane and maleic anhydride-functional polyisoprene. Both species were multifunctional, and therefore capable of interfacial crosslinking. Optical microscopy showed some unusual features including drop clusters, nonspherical drops, and some drops with apparently nonsmooth surfaces. All these features suggest that a crosslinked “skin” covers the interface of the drops. Rheologically, the reactively compatibilized blend showed gel-like behavior in oscillatory experiments, enhanced viscosity and elastic recovery at low stresses, and strong viscosity overshoots in creep experiments, all of which are likely attributable to drop clustering. At the highest stress studied (400Pa), the viscosity of the reactively compatibilized blend is comparable to that of a similar blend compatibilized by diblock copolymer. This suggests that, in practical processing operations that occur at even higher stresses, interfacial crosslinking by multifunctional chains will not adversely affect processability.

In situ reinforcement of poly(butylene terephthalate) and butyl rubber by liquid crystalline polymer

AbstractTernary in situ butyl rubber (IIR)/poly(butylene terephthalate) (PBT) and liquid crystalline polymer (LCP) blends were prepared by compression molding. The LCP used was a versatile Vectra A950, and the matrix material was IIR/PBT 50/50 by weight. Morphological, thermal, and mechanical properties of blends were investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM), differential scanning calorimetry, and thermogravimetric analysis (TGA). Microscopy study (SEM) showed that formation of fibers is increasing with the increasing amount of LCP A950. Microscopic examination of the fractured surface confirmed the presence of a polymer coating on LCP fibrils. This can be attributed to some interactions including both chemical and physical one. The increased compatibility in polymer blends, consisting of IIR/PBT, by the presence of LCP A950 may be explained by the adsorption phenomena of the polymer chains onto the LCP fibrils. SEM and AFM images provided the evidence of the interaction between IIR/PBT and the LCP. Dynamic mechanical analyses (DMA) and TGA measurements showed that the composites possessed a remarkably higher modulus and heat stability than the unfilled system. Storage modulus for the ternary blend containing 50 wt% of LCP exhibits about 94% increment compared with binary blend of IIR/PBT. From the above results, it is suggested that the LCP A950 can act as reinforcement agent in the blends. Moreover, the fine dispersion of LCP was observed with no extensional forces applied during mixing, indicating the importance of interfacial adhesion for the fibril formation. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers

Compatibilized Polymer Blends Based on PDLLA and PCL for Application in Bioartificial Liver

Porous scaffolds for tissue engineering applications based on poly(D,L-lactide)/poly(epsilon-caprolactone) compatibilized blends are described. The addition of a third polymer, namely poly( D, L-lactide-co-caprolactone) copolymer, has a profound effect on morphological properties of the blends scaffolds. In fact, the copolymer acts as compatibilizing agent and reduces the dimension of the dispersed phase of an order of magnitude. Such effect is function of the polymer composition. The efficiency of scaffolds obtained with poly( D, L-lactide) based blends containing 30% by weight of poly(epsilon-caprolactone) as dispersed phase toward hepatocytes has been tested by several biological assays and we found that they are able to promote a perfect adhesion, proliferation and growth of cells. Moreover, the addition of the copolymer significantly improves the biomedical performance of the scaffold.

Viscometric investigation of compatibilization of the poly(vinyl chloride)/poly(ethylene-co-vinyl acetate) blends by terpolymer of maleic anhydride–styrene–vinyl acetate

In this study, a blend of poly(vinyl chloride) (PVC)/ethylene-co-vinyl acetate (EVA) was compatibilized by terpolymer of maleic anhydride–styrene–vinyl acetate (MAStVA) used as a compatibilizer. It was prepared the blends of 50/50 PVC/EVA containing 2–10% of the terpolymer. The compatibility experiences of these blends were investigated by using viscometric method in the range of concentrations (0.5–2.0 g dL −1) where tetrahydrofuran (THF) is the solvent. The interaction parameter (Δ b) was used to study the miscibility and compatibility of polymer blend in solution, obtained from the modified Krigbaum and Wall theory. Turbidity and FTIR measurements were also used to investigate the miscibility of this pair of polymers. The values of the relative viscosities of the each polymer solution and their blends were measured by a Cannon–Fenske type viscometer. In consequence of the study, it was observed that a considerable improvement was achieved in the miscibility of PVC/EVA blends by adding among 5 and 10 wt% of compatibilizer.

Compatibilized polymer blends with nanoscale or sub-micron dispersed phases achieved by hydrogen-bonding effects: Block copolymer vs blocky gradient copolymer addition

Addition of styrene (S)/4-hydroxystyrene (HS) block, blocky gradient, or blocky random copolymer to 80/20wt% polystyrene (PS)/polycaprolactone (PCL) blends is examined as a compatibilization strategy. Four copolymers are synthesized by controlled radical polymerization, each with an S block and the other block being a HS block or S/HS random or gradient copolymer. Compatibilization depends on copolymer level and HS sequence distribution and content. Using a two-step solution-mixing/melt-mixing process, addition of 2wt% and 5wt% nearly symmetric S/HS diblock copolymer leads to compatibilization with average PCL domain diameters of 390–490nm and 90–110nm, respectively. In contrast, adding 0.25–0.75wt% copolymer leads to microscale dispersed-phase domains and only reduced melt-state coarsening. Results with 2–5wt% added copolymer indicate that a major reduction in interfacial tension is facilitated by hydrogen bonding of HS units and PCL carbonyl groups. Nanoscale confinement of normally semi-crystalline PCL within blends with 100nm dispersed phases impedes PCL crystallizability, yielding liquid-state PCL domains at room temperature and demonstrating that properties of nanostructured blends and microstructured blends can differ greatly. Polystyrene/PCL blends are also made by one-step melt mixing with low mol% HS copolymers. Adding 5wt% blocky gradient S/HS copolymer (86/14mol% S/HS) leads to compatibilization with an average dispersed-phase diameter of 360–420nm. In contrast, adding 5wt% blocky random (87/13mol% S/HS) or 5wt% diblock (81/19mol% S/HS) copolymer yields microscale dispersed-phase domains and only reduced coarsening. Crystallization in these blends is less hindered than in blends containing 2–5wt% nearly symmetric S/HS diblock copolymer, indicating that both hydrogen bonding and confinement suppress PCL crystallization.

Varying the blending protocol to control the morphology of model compatibilized polymer blends

AbstractThe structure of an oil/water emulsion is known to depend on its preparation method. Here, we test whether the preparation protocol can be used to control the morphology of “model” blends of immiscible polymers compatibilized by a diblock copolymer. Two preparation protocols were tested. In the “double blending” protocol, a droplet‐matrix blend was blended with additional drop‐phase fluid. As in oil/water emulsions, this yielded a drop‐within‐drop “double emulsion” morphology. Coalescence suppression due to compatibilizer was found crucial to double emulsion stability. The rheology of the double emulsion was qualitatively similar to that of a simple droplet‐matrix blend, but with an effectively higher drop volume fraction. In the “multistep concentration” protocol, the drop phase was added gradually (rather than all‐at‐once) to the matrix phase. While this protocol can realize a high‐dispersed phase emulsion in oil/water systems, in this case, phase inversion occurred when the drop volume fraction exceeded 0.5. © 2008 American Institute of Chemical Engineers AIChE J, 2008