Emulsion Atom Research Articles

Size control of copper nanodrugs through emulsion atom transfer radical polymerization

Cu nanodrugs with diverse sizes (70–440 nm) were prepared through emulsion atom transfer radical polymerization. The relationship between particle size and anticancer activity was investigated.

Oil droplet breakup during pressure swirl atomization of emulsions: Influence of emulsion viscosity and viscosity ratio

The atomization of oil-in-water emulsions for spray drying is a common task in food engineering. During atomization with pressure swirl atomizers, the emulsions are subjected to high stresses that can lead to deformation and breakup not only of the liquid itself but also of the disperse oil droplets therein. In this study, the effect of the viscosity ratio λ of the emulsion (0.2–33) and of the emulsion viscosity (5–50 mPa⋅s) on oil droplet breakup during atomization was investigated at atomization pressures between 50 and 250 bar. A systematic influence of λ on the oil droplet size was observed with maximum oil droplet breakup for λ between 0.2 and 1.2. At a constant viscosity ratio of ∼ 1, the resulting oil droplet size was almost independent of the emulsion viscosity, even when volume flow rates and spray droplet sizes during atomization showed a clear dependence on this parameter. A model based on existing knowledge on droplet breakup in laminar shear flow is developed, by which oil droplet sizes after atomization can be predicted. This model may serve as a tool to control oil droplet size after atomization by defining appropriate atomization conditions and emulsion formulation. This is especially relevant for spray drying applications in which the oil droplet size in the powder is an important quality parameter. • Viscosity ratio λ influences oil droplet breakup during pressure swirl atomization. • At λ ∼ 1 the emulsion viscosity per se has little influence on oil droplet breakup. • Oil droplet breakup follows the theory of droplet breakup in laminar shear flow. • A model is proposed that serves as a tool to predict oil droplet breakup.

Development of the FPDA technique to study the atomization of emulsions

Development of the FPDA technique to study the atomization of emulsions

Investigation of Oil Droplet Breakup during Atomization of Emulsions: Comparison of Pressure Swirl and Twin-Fluid Atomizers

The goal of this study was to investigate oil droplet breakup in food emulsions during atomization with pressure swirl (PS), internal mixing (IM), and external mixing (EM) twin-fluid atomizers. By this, new knowledge is provided that facilitates the design of atomization processes, taking into account atomization performance as well as product characteristics (oil droplet size). Atomization experiments were performed in pilot plant scale at liquid volume flow rates of 21.8, 28.0, and 33.3 L/h. Corresponding liquid pressures in the range of 50–200 bar and air-to-liquid ratios in the range of 0.03–0.5 were applied. Two approaches were followed: oil droplet breakup was initially compared for conditions by which the same spray droplet sizes were achieved at constant liquid throughput. For all volume flow rates, the strongest oil droplet breakup was obtained with the PS nozzle, followed by the IM and the EM twin-fluid atomizer. In a second approach, the concept of energy density EV was used to characterize the sizes of resulting spray droplets and of the dispersed oil droplets in the spray. For all nozzles, Sauter mean diameters of spray and oil droplets showed a power-law dependency on EV. PS nozzles achieved the smallest spray droplet sizes and the strongest oil droplet breakup for a constant EV. In twin-fluid atomizers, the nozzle type (IM or EM) has a significant influence on the resulting oil droplet size, even when the resulting spray droplet size is independent of this nozzle type. Overall, it was shown that the proposed concept of EV allows formulating process functions that simplify the design of atomization processes regarding both spray and oil droplet sizes.

Kinetics of MMA Atom Transfer Radical Polymerization Initiated by Reducing Agent in Stirred Batch Emulsion Reactor

AbstractAb initio emulsion atom transfer radical polymerization (ATRP) differs from regular emulsion polymerization because the kinetic and thermodynamic aspects of each process are very unlikely alike. This paper presents a kinetic analysis of activator generated by electron transfer (AGET) ATRP of methyl methacrylate (MMA) in a stirred emulsion reactor. The focus of the study is to assess the variation of the monomer content in the organic phase and the rate polymerization for different reaction temperatures, as well as the impact of surfactant content and stirring speed on latex stability. Poly(methyl methacrylate) (PMMA) polymer samples are analyzed by means of gravimetry, dynamic light scattering, gel permeation chromatography, and HNMR techniques to determine monomer conversion, polymer particle diameter, molecular weight distribution, and polymer molecular structure, respectively. The results show the production of PMMA of narrow polydispersity index (Ð) and low molar mass (Mn) for MMA conversion around 60% and detect two‐regions instead of a three‐regions trend of rate of polymerization (Rp) as conventional emulsion polymerization. The reaction rate increases during the nucleation stage and then flattens over an invariant trend which confirms a living feature of the AGET ATRP polymerization. The average number of radicals per latex particle (ñ) is also debated.

Experimental Investigation of Methyl Methacrylate in Stirred Batch Emulsion Reactor: AGET ATRP Approach.

This study examines the ab initio emulsion atom transfer radical polymerization (ATRP) initiated by an eco-friendly reducing agent to produce poly(methyl methacrylate) (PMMA) polymer with controlled characteristics in a 2 L stirred batch reactor. The effect of the reaction temperature, surfactant concentration, monomer to water ratio, and stirring speed was thoroughly investigated. The results showed that PMMA coagulation becomes quite severe at a certain temperature threshold. However, the coagulation could be avoided at mild reaction temperature, since the outcomes showed that loading more surfactant to the system under high mixing speed has balanced the polymer mixture and yielded high monomer conversion. The PMMA product was analyzed by gravimetry and GPC measurements and after 5 h of polymerization at a reaction temperature of 50 °C, monomer conversion of 64.1% was obtained, and PMMA polymer samples produced had an average molar mass of 4.5 kg/mol and a polydispersity index of 1.17. The structure of the PMMA polymer was successfully proved by FTIR and nuclear magnetic resonance (NMR) spectroscopy. The results confirm the living feature of MMA AGET ATRP in emulsion medium and recommend further investigation for other types of surfactant.

Changes in oil-in-water emulsion size distribution during the atomization step in spray-drying encapsulation

During atomization of emulsions, dispersed oil droplets are susceptible to breakup changing the emulsion size distribution, a critical parameter in encapsulation applications. We investigated the influence of the different atomization parameters on the size and size distribution of the sprayed emulsion and defined rules for the choice of conditions which will make it possible to maintain a specific emulsion size.Oil-in-water emulsions were prepared with different aqueous phase viscosity, oil fraction, and emulsion droplet size and sprayed with two different atomization systems: a two-fluid nozzle with external mixing and a rotary atomizer.For both systems, two different breakup regimes were identified: (1) monomodal and (2) bimodal distribution breakup; and a critical Capillary number was determined for each breakup regime.These findings can be used to predict oil droplet breakup and define the right atomization conditions and/or emulsion formulation for controlling sprayed emulsion structure in microencapsulation applications.

Supercritical Assisted Atomization of emulsions for encapsulation of 1-monoacylglycerols in an hydrophilic carrier

A new approach for the production of microspheres from oil-in-water (O/W) emulsions using supercritical fluids is presented. The composition of the emulsions, consisting of 1-monoacylglycerol (1-MAG) and polyvinylalcohol (PVA) was first optimized, then supercritical assisted atomization (SAA) was applied to produce dried microparticles. The effect of different 1-MAG/PVA ratios and emulsion preparation method on size, stability, and morphology of microparticles was investigated using scanning electron microscopy, dynamic light scattering, differential scanning calorimetry and X-ray diffraction. The emulsion composition and emulsification method affected the sizes of microparticles and the smallest 1-MAG/PVA microparticles were obtained at lower 1-MAG (<30mg/mL) and PVA (6mg/mL) concentrations. Prepared 1-MAG/PVA microparticles had a spherical morphology with mean diameter ranging from 0.5 to 3μm and a semi-crystalline structure. A maximum microparticle recovery of 55% was obtained.

Surfactant–Ligand Design for ab Initio Emulsion Atom Transfer Radical Polymerization

We report an ab initio emulsion atom transfer radical polymerization (ATRP) based on micellar nucleation. A surfactant–ligand (SL) was designed and synthesized for this purpose. The SL design was an amphiphilic macromolecule, and it acted as the surfactant for micelle formation and as the ligand for ATRP catalyst. The micelles were converted into to polymer particles with both water-soluble and oil-soluble initiators. The micellar nucleation mechanism was confirmed by the growth of polymer particles during polymerization, in comparison to a control experiment without SL addition. It was also found that diffusion-controlled deactivation inside particles occurred, which broadened the polymer molecular weight distribution. Adding a small amount of free catalyst significantly improved the molecular weight control. The polymers resulting from the ab initio emulsion ATRP were proven living by chain extension experiments.

PMMA‐co‐PHFBA‐co‐PHPA acrylic fluoropolymers via an ab initio emulsion atom transfer radical polymerisation with activators regenerated by electron transfer

PurposeThe purpose of this paper is to synthesise the tercopolymer PMMA‐co‐PHFBA‐co‐PHPA in an ab initio emulsion through activators regenerated by electron transfer for atom transfer radical polymerisation in the absence of F‐containing surfactant and organic assistants.Design/methodology/approachTo produce the tercopolymer of methyl methacrylate, hexafluorobutyl acrylate, and 2‐hydrothyl propyl acrylate with a precise macromolecular composition and structure, water used as the dispersion medium, Tween‐80 and SDS as emulsifiers, soluble ascorbic acid as the reducing agent and benzyl bromide as the initiator. The catalyst was CuBr2/O‐phenanthroline complex. The molecular structure of the polymer was characterised by FT‐IR, Raman, and 1H‐NMR. Molecular weight and molecular weight distributions were measured by gel permeation chromatography.FindingsThe polymer molecular composition and structure are controllable during polymerisation as defined without nitrogen protection. However, the average molecular weight of the polymer deviates from the theoretical value when the monomer fractional conversion reaches 90 percent. The molecular weight distribution of the polymer (PDI=1.4) is much broader than those done in bulk or solution polymerisation.Originality/valueIntegrating ab initio emulsion with activators regenerated by electron transfer via atom transfer radical polymerisation (ARGET‐ATRP) technologies could be a significant method for producing functional acrylic‐fluoropolymer with defined macromolecular composition and structure, even in the absence of F‐containing surfactant and organic assistants, both of which are necessary in the normal case.

Uniform star‐polystyrene nanoparticles prepared by emulsion atom transfer radical polymerization

AbstractPentaerythritol (PT) was converted into four‐arm initiator pentaerythritol tetrakis(2‐chloropropionyl) (PT‐Cl) via reaction with 2‐chloropropionyl chloride. Uniform (monodisperse) star‐polystyrene nanoparticles were prepared by emulsion atom transfer radical polymerization of styrene, using PT‐Cl/CuCl/bpy (bpy is 2,2′‐dipyridyl) as the initiating system. The structures of PT‐Cl and polymer were characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance. The morphology, size and size distribution of the star‐polystyrene nanoparticles were characterized by transmission electron microscopy, atomic force microscopy and photon correlation spectroscopy. It was found that the average diameters of star‐polystyrene nanoparticles were smaller than 100 nm (30–90 nm) and monodisperse; moreover, the particle size could be controlled by the monomer/initiator ratio and the surfactant concentration. The average hydrodynamic diameter (Dh) of the nanoparticles increased gradually on increasing the ratio of styrene to PT‐Cl and decreased on enhancing the surfactant concentration or increasing the catalyst concentration. Copyright © 2011 Society of Chemical Industry

Preparation of monodisperse nanoparticles containing poly(propylene imine)(NH2)32‐polystyrene

AbstractPolypropylenimine dendrimer (DAB‐Am‐32, generation 4.0) was converted into a macroinitiator DAB‐Am‐32‐Cl via reaction with 2‐chloropropionyl chloride. Monodisperse nanoparticles containing poly(propylene imine)(NH2)32‐polystyrene were prepared by emulsion atom transfer radical polymerization (ATRP) of styrene (St), using the DAB‐Am‐32‐Cl/CuCl/bpy as initiating system. The structure of macroinitiator was characterized by FTIR spectrum, 1H NMR, and 13C NMR. The structure of poly(propylene imine)(NH2)32‐polystyrene was characterized by FT‐IR spectrum and 1H NMR; the molecular weight and molecular weight distribution of poly(propylene imine)(NH2)32‐polystyrene were characterized by gel permeation chromatograph (GPC). The morphology, size and size distribution of the nanoparticles were characterized by photon correlation spectroscopy (PCS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The effects of monomer/macroinitiator ratio and surfactant concentration on the size and size distribution of the nanoparticles were investigated. It was found that the diameters of the nanoparticles were smaller than 100 nm (30–80 nm) and monodisperse; moreover, the particle size could be controlled by monomer/macroinitiator ratios and surfactant concentration. With the increasing of the ratio of St/DAB‐Am‐32‐Cl, the number‐average diameter (Dn), weight‐average diameter (Dw) were both increased gradually. With enhancing the surfactant concentration, the measured Dh of the nanoparticles decreased, while the polydispersity increased. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2892–2904, 2009

Block copolymer preparation by atom transfer radical polymerization under emulsion conditions using a nanoprecipitation technique

AbstractLiving‐radical polymerization of acrylates were performed under emulsion atom transfer radical polymerization (ATRP) conditions using latexes prepared by a nanoprecipitation technique previously employed and optimized for the polymerization of styrene. A macroinitiator of poly(n‐butyl acrylate) prepared under bulk ATRP was dissolved in acetone and precipitated in an aqueous solution of Brij 98 to preform latex particles, which were then swollen with monomer and heated. Various monomers (i.e. n‐butyl acrylate, styrene, and tert‐butyl acrylate) were used to swell the particles to prepare homo‐ and block copolymers from the poly(n‐butyl acrylate) macroinitiator. Under these conditions latexes with a relatively good colloidal stability were obtained. Furthermore, amphiphilic block copolymers were prepared by hydrolysis of the tert‐butyl groups and the resulting block copolymers were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The bulk morphologies of the polystyrene‐b‐poly(n‐butyl acrylate) and poly(n‐butyl acrylate)‐b‐poly(acrylic acid) copolymers were investigated by atomic force microscopy (AFM) and small angle X‐ray scattering (SAXS). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 625–635, 2008

Development of an ab Initio Emulsion Atom Transfer Radical Polymerization: From Microemulsion to Emulsion

Atom transfer radical polymerization (ATRP) has been successfully extended to an ab initio emulsion system using a "two-step" procedure, in which the final emulsion polymerization system was formed by adding monomer to an ongoing microemulsion ATRP. The newly developed AGET (activators generated by electron transfer) initiation technique was employed in the first stage of this ab initio ATRP. It allows using oxidatively stable Cu(II) species that is reduced in situ by ascorbic acid. The surfactant concentration in the final emulsion system was efficiently decreased to approximately 2 wt % (approximately 10 wt % vs monomer) by decreasing the catalyst concentration and changing the ratio of the monomer added at the microemulsion stage to the monomer added during the second stage. This two-step procedure avoids the necessity of transporting catalysts through the aqueous media during polymerization, resulting in a controlled emulsion polymerization, as evidenced by a linear first-order kinetic plot and formation of a polymer with a relatively narrow molecular weight distribution (Mw/Mn = 1.2-1.4). The polymerization typically reached 70-90% monomer conversion in 5-6 h. The resulting polymer had high chain-end functionality and was successfully chain extended to form in situ block copolymers by adding the second monomer to an ongoing emulsion polymerization. The stable latex from the ab initio emulsion ATRP had a particle size approximately 120 +/- 10 nm.

Living radical emulsion polymerization using the nanoprecipitation technique: An extension to atom transfer radical polymerization

AbstractLiving radical polymerizations of styrene were performed under emulsion atom transfer radical polymerization conditions with latexes prepared by a nanoprecipitation technique recently developed for the stable free‐radical polymerization process. Latexes were prepared by the precipitation of a solution of low‐molecular‐weight polystyrene in acetone into a solution of a surfactant in water. The resulting particles were swollen with styrene and then heated. The effects of various surfactants and hydrophobic ligands, the reaction temperature, and the ligand/copper(I) bromide ratio were studied. The best results were obtained with the nonionic surfactant Brij 98 in combination with the hydrophobic ligand N,N‐bis(2‐pyridylmethyl)octadecylamine and a ligand/copper(I) bromide ratio of 1.5 at a reaction temperature of 85–90 °C. Under these conditions, latexes with good colloidal stability with average particle diameters of 200 nm were obtained. The molecular weight distributions of the polystyrenes were narrow, although the experimental molecular weights were slightly larger than the theoretical ones because not all the macroinitiator appeared to reinitiate. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4027–4038, 2006

Emulsion atom transfer radical block copolymerization of 2‐ethylhexyl methacrylate and methyl methacrylate

AbstractThe emulsion atom transfer radical block copolymerization of 2‐ethylhexyl methacrylate (EHMA) and methyl methacrylate (MMA) was carried out with the bifunctional initiator 1,4‐butylene glycol di(2‐bromoisobutyrate). The system was mediated by copper bromide/4,4′‐dinonyl‐2,2′‐bipyridyl and stabilized by polyoxyethylene sorbitan monooleate. The effects of the initiator concentration and temperature profile on the polymerization kinetics and latex stability were systematically examined. Both EHMA homopolymerization and successive copolymerization with MMA proceeded in a living manner and gave good control over the polymer molecular weights. The polymer molecular weights increased linearly with the monomer conversion with polydispersities lower than 1.2. A low‐temperature prepolymerization step was found to be helpful in stabilizing the latex systems, whereas further polymerization at an elevated temperature ensured high conversion rates. The EHMA polymers were effective as macroinitiators for initiating the block polymerization of MMA. Triblock poly(methyl methacrylate–2‐ethylhexyl methacrylate–methyl methacrylate) samples with various block lengths were synthesized. The MMA and EHMA reactivity ratios determined by a nonlinear least‐square method were ∼0.903 and ∼0.930, respectively, at 70 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1914–1925, 2006

Synthesis and characterization of poly(n‐butyl methacrylate)‐b‐polystyrene diblock copolymers by atom transfer radical emulsion polymerization

AbstractPoly(n‐butyl methacrylate) (PBMA)‐b‐polystyrene (PSt) diblock copolymers were synthesized by emulsion atom transfer radical polymerization (ATRP). PBMA macroinitiators that contained alkyl bromide end groups were obtained by the emulsion ATRP of n‐butyl methacrylate with BrCH3CHCOOC2H5 as the initiator; these were used to initiate the ATRP of styrene (St). The latter procedure was carried out at 85°C with CuCl/4,4′‐di(5‐nonyl)‐2,2′‐bipyridine as the catalyst and polyoxyethylene(23) lauryl ether as the surfactant. With this technique, PBMA‐b‐PSt diblock copolymers were synthesized. The polymerization was nearly controlled; the ATRP of St from the macroinitiators showed linear increases in number‐average molecular weight with conversion. The block copolymers were characterized with IR spectroscopy, 1H‐NMR, and differential scanning calorimetry. The effects of the molecular weight of the macroinitiators, macroinitiator concentration, catalyst concentration, surfactant concentration, and temperature on the polymerization were also investigated. Thermodynamic data and activation parameters for the ATRP are also reported. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2123–2129, 2005

Emulsion atom transfer radical polymerization of 2-ethylhexyl methacrylate

The emulsion atom transfer radical polymerization (ATRP) of 2-ethylhexyl methacrylate (EHMA) was carried out with ethyl 2-bromoisobutyrate (EBiB) as an initiator and copper bromide (CuBr)/4,4′-dinonyl-2,2′-bipyridyl (dNbpy) as a catalyst system. The effects of surfactant type and concentration, temperature, monomer/initiator ratio, and CuBr 2 addition on the system livingness, polymer molecular weight control, and latex stability were examined in detail. It was found that the polymerization systems with Tween 80 and Brij 98 as surfactants at 30 °C gave the best latex stability. The polymer samples prepared under these conditions had narrow molecular weight distributions ( M w/ M n=1.1–1.2) and linear relationships of number-average molecular weight versus monomer conversion.

Synthesis and characterization of PBMA-b-PSt-b-PBMA triblock copolymers by atom transfer radical emulsion polymerization

Poly(n-butyl methacrylate)-b-polystyrene-b-poly(n-butyl methacrylate) (PBMA-b-PSt-b-PBMA) triblock copolymers were successfully synthesized by emulsion atom transfer radical polymerization (ATRP). Difunctional polystyrene (PSt) macroinitiators that contained alkyl chloride end-groups were prepared by ATRP of styrene (St) with CCl4 as initiator and were used to initiate the ATRP of butyl methacrylate (BMA). The latter procedure was carried out at 85°C with CuCl/4,4-di (5-nonyl)-2,2- bipyridine (dNbpy) as catalyst and polyoxyethylene (23) lauryl ether (Brij35) as surfactant. Using this technique, triblock copolymers consisting of a PSt center block and PBMA terminal blocks were synthesized. The polymerization was nearly controlled, ATRP of St from those macroinitiators showed linear increases in the number average molecular weight (Mn) with conversion. The block copolymers were characterized with infrared (IR) spectroscopy, hydrogen-1 nuclear magnetic resonance (1HNMR), and differential scanning calorimetry (DSC). The effects of the molecular weight of macroinitiators, concentration of macroinitiator, catalyst, emulsion, and temperature on the polymerization were also investigated. Thermodynamic data and activation parameters for the ATRP were also reported

Method for electrostatic atomization of emulsions in an EHD system

In order to atomize oil in an electrohydrodynamic (EHD) system, the conductivity must be in the optimum range. The conductivity of pure oil is too low, requiring the addition of 3–20% surfactant to reach the correct conductivity. Adding water increases the conductivity too much, so emulsions cannot be atomized. In this study, a liposome-containing, water-in-oil emulsion was developed which allows water to be added to oil without greatly increasing the conductivity, and also allows oil to be atomized with minimal additives. Oil was emulsified with 0.01% lecithin and 0.3–50% water and atomized electrostatically. Extra virgin olive oil, soybean oil, sunflower oil, corn oil, butter and peanut oil with added aspartame, GDL, Folic acid, B12, Dijon flavor and Red 3 were sprayed onto six kinds of crackers and glass cover slides to demonstrate that reproducible, efficient coatings can be produced using this method. Emulsions up to 20% water produce good atomization. Over 25% water, the droplet-size increases and reproducibility decreases. A liquid crystal phase in the emulsion restricted the conductivity of the water phase to keep the overall conductivity low. Under high electric fields, elongation, chaining, coalescence or breaking of the droplets increases the conductivity enough to permit atomization.