Monomer Droplet Size Research Articles

Polystyrene Particle Size Distribution with the Use of Modified Time Increment Monte Carlo Model

AbstractIn the present study, a dynamic Monte Carlo (MC) model is applied for predicting the dynamic evolution of monomer Droplet Size Distribution (DSD) and polymer Particle Size Distribution (PSD) within the presence of an inventive time step in the MC algorithm for both non‐reactive (liquid–liquid dispersion) and reactive systems. Besides, a combining approach as a second inventive strategy is introduced for implementing the MC simulation with a high number of droplets. An optimization process generated the dimensionless Model Parameters (MPs) and is applied to the MC simulation. The MC algorithm is validated with the experimental data from the literature. The novel time step can predict the dynamic evolution of monomer droplets and polymer particles in the reactive systems and diminish the time of the simulation. The combining approach is an excellent strategy for mixing the same or different number of droplets for decreasing time consumption of MC simulation. Extraordinary findings depicted the model's effectiveness and the validity of the time step and combining strategies.

Free-radical polymerization in a droplet with initiation at the interface

The free-radical polymerization inside monomer droplets surrounded by an immiscible liquid of the initiator solution is studied before the gel effect by means of the generalized method of moments taking into account diffusion of radicals and polymer chains. The influence of the droplet radius and initiator concentration in the surrounding phase on the polymerization kinetics and molecular mass characteristics of the synthesized polymer is analyzed. It is found that the polymerization kinetics matches the bulk polymerization when the droplet is small enough (kinetic regime). However, increasing the droplet radius leads to a diffusion-kinetic regime, in which the polymerization rate becomes significantly lower. As a result, the average length and the dispersity of the produced polymer chains depend significantly on the monomer droplet size. The dependence of the effective polymerization rate coefficient on the droplet radius and the initiator concentration is discussed.

Aqueous RAFT polymerization-induced self-assembly (PISA): amphiphilic macroRAFT self-assembly vs. monomer droplet nucleation (miniemulsion polymerization)

The effect of monomer droplet size on the particle formation mechanism in aqueous heterogeneous polymerization using a hydrophilic macroRAFT agent has been investigated.

Gamma irradiation-induced pH-responsive poly(methyl methacrylate- acrylic acid-divinyl benzene) hybrid polymer particles for dye treatment

ABSTRACT The environmentally friendly method is used to fabricate spherical poly(methyl methacrylate-methyl acrylate-divinylbenzene) (P(MMA-MA-DVB)) hybrid particles by gamma irradiation-induced suspension polymerization without an initiator. The MMA: MA: DVB of 60: 20: 20 was used to encapsulate 10 wt% oleic coated-magnetic nanoparticles using ultrasonication for monomer droplet preparation. A stable suspension with approximately 90% monomer conversion was produced using 5 kGy gamma-ray to initiate the polymerization. A large quantity of submicrometer-sized free polymer particles as a by-product was formed in an aqueous medium where the radicals were generated by gamma irradiation of water. However, the number of free polymer particles decreased with the decrease in monomer droplet size. The obtained particles were hydrolyzed to form P(MMA-AA-DVB) particles presenting a negative surface charge (> −30 mV) in an alkaline condition. It was found that the prepared particles presented dye adsorption efficiency as the methylene blue (MB) concentration reduced with adsorption time. The MB adsorption efficiency also increased with pH due to the presence of PAA as a pH-responsive material. Moreover, the hybrid polymer particles were easily separated by the application of an external magnet. Therefore, the fabricated pH-responsive hybrid polymer particles would be served as an alternative dye adsorbent for wastewater treatment.

Synthesis of Spherical Polymer Nanoparticles Reflecting Size of Monomer Droplets Formed by Tandem Acoustic Emulsification

We have successfully synthesized polymer nanoparticles which reflect precisely the size of monomer droplets formed by the tandem acoustic emulsification. This new synthetic method involves sequenti...

Evolution of droplet size distribution and composition in miniemulsions

ABSTRACTA fundamental understanding of the formation, degradation and polymerization of miniemulsions has been hindered by difficulties in quantifying their monomer droplet size distribution (DSD). In this work, particle sizing techniques including capillary hydrodynamic fractionation, acoustic attenuation spectroscopy, surfactant titration, and microscopy were adapted to characterize miniemulsion DSDs. The key ingredient in miniemulsions is the costabilizer, a low water solubility compound that limits monomer diffusion from the smaller to larger droplets (Ostwald ripening). The DSD evolution of styrene miniemulsions employing hexadecane (HD) as costabilizer was characterized. With less costabilizer, droplets were initially smaller, but increased in average size with time, and their DSDs broadened. These changes were slowed with addition of extra surfactant after homogenization. After several days, the average droplet size increased to about 150 nm regardless of the amount of HD or surfactant used. The HD content of separated portions of centrifuged miniemulsions was measured and showed significant Ostwald ripening within minutes after preparation. The further evolution of the DSD is attributed primarily to droplet coalescence. Less composition change occurred with either higher HD content or post‐homogenization surfactant addition, both of which led to minimization of free energy, increasing stability. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1529–1544

Hybrid copolymer latex of MMA-BA-zonyl TM-PDMS by mini-emulsion polymerization

Stable, coagulum free fluoro-silicone-acrylic latex (FSAL) of methyl methacrylate (MMA)-co-butyl acrylate (BA)-co-Zonyl TM-hyb-Polydimethylsiloxane (PDMS) is prepared through mini-emulsion polymerization. Apart from this, three more latexes/emulsions acrylic latex (AL) of methyl methacrylate (MMA)-co-butyl acrylate (BA), silicone-acrylic latex (SAL) of methyl methacrylate (MMA)-co-butyl acrylate (BA)-hyb- PDMS, and fluoro acrylic latex (FAL) of methyl methacrylate (MMA)-co-butyl acrylate (BA)-co-Zonyl TM are prepared for systematic understanding of the preparation and properties of the emulsions. The emulsions are prepared with almost uniform size of monomer droplets (mini-emulsions). The prepared latexes were characterized by IR, C13 NMR and 1H NMR. A systematic understanding of the effect of initial droplet size on final latex particle, the properties of the latex particles such as swelling ratio, MFFT, contact angle, distribution of particle size, rheological behavior, DSC/DMA thermograms, SEM images of the films and film topography are reported. The fluoro-silicone-acrylic latex (FSAL) exhibit, stable, low MFFT, narrow particle size distribution, and high contact angle for water, and hence it can be a great candidate as a hydrophobic binder in coating products.

Styrene Miniemulsion Polymerization: Incorporation of N‐Alkanes

AbstractSummary: In this work, the incorporation of alkane hydrocarbons in poly(styrene‐co‐methacrylic acid) particles via miniemulsion polymerization was investigated. The reactions were performed at 80 °C for 4 hours, using benzoyl peroxide as oil‐soluble initiator. The effects of different concentrations of a hydrophilic co‐monomer (methacrylic acid) and different types and concentrations of alkanes, namely n‐hexadecane, n‐octane and n‐heptane were evaluated. Miniemulsion stability at room temperature and reaction kinetics were monitored, as well as the particles size and morphology. Results show the viability of encapsulation of alkanes in miniemulsion polymerizations, especially of alkanes with intermediate chain lengths (e.g. n‐hexadecane). When short chain alkanes are incorporated the miniemulsions become less stable, due to their lower hydrophobicity. Based on monomer droplet size distribution data, it was determined that the best concentration of hydrophilic co‐monomer for the studied system was 1.0 wt%.

Syntheses of Ethyl Cellulose Acrylate Hybrid Latex via Mini-Polymerization

Ethyl cellulose was hybridized with methyl methacrylate and butyl acrylate via mini-polymerization. The polymerization process was traced to obtain a stable reaction system. The effects of the EC content and viscosity on the monomer droplet size, the particle size and the monomer conversion were investigated. It was showed that the stability of the latex dispersion was strongly dependent of the EC content and viscosity. With investigation on ethyl cellulose series, initiator and crosslinker, the stable mini-emulsion with 10% ethyl cellulose was obtained under conditions of crosslinker and LPO as initiator.

Electrochemical Reaction of Water-Insoluble Organic Droplets in Aqueous Electrolytes Using Acoustic Emulsification

Electrochemical oxidation of water-insoluble amines (n-octylamine and n-decylamine) was successfully accomplished in aqueous electrolytes using acoustic emulsification. Acoustically prepared emulsions of fumaric acid diethyl ester in aqueous electrolytes can be also electro-reduced very smoothly. Ultrasonication to the water-insoluble organic substrate/aqueous electrolyte mixtures allowed a formation of very stable emulsions having the characteristic of giving narrow monomer droplet size distributions in the submicrometer range in aqueous electrolytes without added surfactants, and the smooth electrochemical reaction in the emulsions took place via direct electron transfer between the electrode and the water-insoluble organic droplets. In this kind of electron-transfer system, supporting electrolyte should be dissolved not only in the aqueous phase but also in the organic droplets and should contribute to the formation of an electric bilayer inside the droplets.

On‐line acoustic attenuation spectroscopy of emulsions stabilized by vinyl alcohol–vinyl acetate copolymers: a model system for the suspension polymerization of vinyl chloride

AbstractBACKGROUND: Poly[(vinyl alcohol)‐co‐(vinyl acetate)] (PVA) copolymers obtained by partial hydrolysis of poly(vinyl acetate) are currently used as industrial stabilizers in the suspension polymerization of vinyl chloride monomer (VCM). Their molecular characteristics, mainly the average degree of hydrolysis (DH) and average degree of polymerization (DPw), have a major influence on the monomer droplet size and the properties of the final poly(vinyl chloride) resin.RESULTS: The average droplet size and size distribution of chlorobutane/water emulsions, as a model system for VCM/water emulsions, were studied using acoustic attenuation spectroscopy on‐line with an agitated laboratory reactor. The emulsions were stabilized by PVA with DH values between 73 and 88 mol% and DPw values between 450 and 2500. The effects of agitation speed, stirring time and concentration of the PVA copolymers were investigated. An attempt was made to correlate the interfacial tension and the droplet size.CONCLUSION: On‐line acoustic spectroscopy appears to be a suitable technique for the real‐time control of the droplet size of monomer suspensions. The advantages and limitations of the technique are outlined. The validity and the application limits of the commonly cited correlation between the droplet size and the Weber number are established for polymeric surfactant‐stabilized emulsions. Copyright © 2009 Society of Chemical Industry

Simultaneous Monitoring of Polymer and Particle Characteristics during Emulsion Polymerization

Emulsion polymerization reactions constitute complex, nonequilibrium systems in which there is strong interaction between polymers, monomers, and the colloidal structures that mediate the reactions. A novel and general method was sought to monitor emulsion polymerization reactions. Instrumentation and methods were hence developed here to achieve, for the first time, simultaneous monitoring of the evolving characteristics of both the organosoluble components (monomer conversion, polymer molar mass, and reduced viscosity) and the colloidal components (particle size of monomer droplets and nucleated polymer particles). No empirical models were required for these determinations. This represents a new capability for the broadening ACOMP platform (automatic continuous online monitoring of polymerization reactions). The method was applied to free radical emulsion homopolymerization of methyl methacrylate and butyl acrylate over a wide monomer concentration range, with and without surfactant stabilization. A succ...

Development of a Novel Environmentally Friendly Electropolymerization of Water-Insoluble Monomers in Aqueous Electrolytes Using Acoustic Emulsification

Electropolymerization of water-insoluble monomers, such as 3,4-ethylenedioxythiophene (EDOT), 3,4-dimethylthiophene (3,4-DiMeTh), 3-methylthiophene (3-MeTh), and 3-ethylthiophene (3-EtTh), proceeded successfully in aqueous electrolytes using acoustic emulsification. Ultrasonication to the water-insoluble monomer/aqueous electrolyte mixtures allowed the formation of very stable emulsions having the characteristic of giving narrow monomer droplet size distributions in the submicrometer range in aqueous electrolytes without added surfactants, and the smooth electropolymerization in the emulsions took place via direct electron transfer between the electrode and the water-insoluble monomer droplets. In this kind of electron-transfer system, the supporting electrolyte should be dissolved not only in the aqueous phase but also in the monomer droplets and contribute to the formation of an electric bilayer inside the droplets. The properties of a polymer EDOT film obtained by the present method were also investigated.

Novel Experimental Technique for the Determination of Monomer Droplet Size Distribution in Miniemulsion

AbstractSummary: The lack of accurate knowledge for measuring monomer droplet size and droplet size distribution has hampered the further progress of miniemulsion polymerization. Monomer droplet size is probably the most important characteristics of a miniemulsion, influencing the miniemulsion stability and the nucleation mechanism. To date, several experimental techniques have been tested to measure miniemulsion droplet size, but none are convenient and accurate. This work presents a novel experimental technique, using a powerful new scanning transmission electron microscopy (STEM) imaging system, which allows transmission observations of wet samples in an environmental scanning electron microscopy (ESEM). This new imaging technique is a useful technique to directly measure droplet size and droplet size distribution.Miniemulsion droplets in dark field wet STEM imaging conditions.magnified imageMiniemulsion droplets in dark field wet STEM imaging conditions.

Monodisperse micron-sized polystyrene particles by seeded polymerization using reactive macrosurfactants

Monodisperse micron-sized polystyrene particles could be prepared through a two-staged seeded swelling and polymerization method using reactive surfactants. The seed was obtained by emulsifier-free emulsion polymer- ization. To prepare conventional surfactant-free monomer emulsion droplet in swelling process, a tri-block diol diacrylate (t-BDDA), which is poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) tri-block copolymer containing two chain ends capped with acryloyl chloride, was employed as a reactive surfactant instead of con- ventional surfactants. Thermodynamic consideration of the effect of monomer droplet size and interfacial tension on the swelling process ensured that two-staged monomer swelling could be effectively performed by using t-BDDA as a surface-active macromonomer. From the surface tension measurement and optical microscope observation, it was found that the t-BDDA had a favorable surface activity when the monomer emulsion was prepared under its cloud point. From the X-ray photoelectron spectroscopy, it was found that most of the t-BDDA resided on the final particle surfaces.

A polyampholyte triblock copolymer synthesized for using as the surfactant of miniemulsion polymerization and production of highly uniform microspheres

Miniemulsions based on styrene/azobisisobutyronitrile (AIBN) in the presence of polyampholyte triblock copolymers as a surfactant and hexadecane (HD) as a cosurfactant were developed. The polyampholyte was prepared by using methyl methacrylate (MMA), methacrylic acid (MAA), and 2-(dimethylamino) ethyl methacrylate (DMAEMA) as monomers. For the sake of comparison, a miniemulsion polymerization with sodium dodecyl sulfate (SDS) was carried out using the same procedure as the above series. The monomer droplet sizes and their shelf life tests revealed that the polyampholyte could stabilize miniemulsion and lead nucleation mechanisms to droplet nucleation. Miniemulsion polymerization using SDS as the surfactant possess a higher polymerization rate than that of polyampholyte, probably due to the smaller droplet size. Production of uniform microspheres was also carried out in this work. Highly uniform microspheres prepared using polyampholyte as the surfactant in the presence of acetone could be obtained. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2230–2237, 2003

Miniemulsion polymerization of styrene in the presence of a water-insoluble blue dye

Relatively stable styrene (ST) miniemulsions were prepared by using a water-insoluble, low molecular weight blue dye as the cosurfactant. The data of the monomer droplet size, creaming rate and phase separation of the monomer as a function of time, were used to evaluate their shelf stability. The dye concentration in toluene can be determined by UV absorbance at 678 nm. This makes the dye molecule a potential probe for determining the loci of particle nucleation during miniemulsion polymerization. In the subsequent miniemulsion polymerization, latex particles were produced via both the monomer droplet nucleation and homogeneous nucleation. Approximately 60% of the original monomer droplets was successfully nucleated during polymerization based on the data of the weight percentage of dye incorporated into the final latex particles ( P dye). The parameter P dye goes up with increasing [dye] (0.1%→1.0% based on total monomer), which is attributed to the increased resistance against diffusional degradation of the monomer droplets. This may greatly reduce the number of primary particles nucleated in the aqueous phase and, thereby, increase the degree of incorporation of dye into the final latex particles. Conductivity measurements during polymerization also support the mixed modes of particle nucleation.

Miniemulsion polymerization of styrene using alkyl methacrylates as the reactive cosurfactant

Stable styrene miniemulsions were prepared by using alkyl methacrylates as the reactive cosurfactant. Like conventional cosurfactants (e.g., cetyl alcohol (CA) and hexadecane (HD)), alkyl methacrylates (e.g., dodecyl methacrylate (DMA) and stearyl methacrylate (SMA)) may act as a cosurfactant in stabilizing the homogenized miniemulsions. Furthermore, the methacrylate group may be chemically incorporated into latex particles in subsequent miniemulsion polymerization. The data of the monomer droplet size, creaming rate and phase separation of monomer as a function of time were used to evaluate the shelf-life of miniemulsions stabilized by sodium dodecyl sulfate in combination with various cosurfactants. Polystyrene latex particles were produced via both monomer droplet nucleation and homogeneous nucleation in the miniemulsion polymerization using CA or DMA as the cosurfactant, with the result of a quite broad particle size distribution. On the other hand, the miniemulsion polymerization with HD or SMA showed a predominant monomer droplet nucleation. The resultant particle size distribution was relatively narrow. In miniemulsion polymerization, the less hydrophobic DMA is similar to CA, whereas the more hydrophobic SMA is similar to HD.

Miniemulsion polymerization of methyl methacrylate with dodecyl mercaptan as cosurfactant

Miniemulsions of methyl methacrylate with sodium lauryl sulfate as the surfactant and dodecyl mercaptan (DDM) as the cosurfactant (or hydrophobe) were prepared and polymerized. The emulsions were of a droplet size range common to miniemulsions and exhibited long-term stability (greater than 3 months). Results indicate that DDM retards Ostwald ripening and allows the production of stable miniemulsions. When these emulsions were initiated, particle formation occurred predominantly by monomer droplet nucleation. The effects of the concentration of surfactant, cosurfactant and initiator were determined. Rates of polymerization, monomer droplet sizes, polymer particle sizes, molecular weights of the polymer, and the effect of initiator concentration on the number of particles vary systematically in ways that indicate predominant droplet nucleation in these systems. © 1996 John Wiley & Sons, Inc.

Effect of Surfactant Configurations on Miniemulsion Polymerization

In the adsorbed state, the molecular area (A c ) of fatty alcohol (FA) decreases and the hydrodynamic layer thickness (δ) of mixedsurfactant (FA + sodium dodecyl sulfate, SDS) increases with increasing alkyl chain length of FA. In bulk solution, the hydrodynamic volume of mixed-surfactant (FA+ SDS) increases with increasing alkyl chain length of FA. In both states the FAs were solubilized by SDS. These results reflect that a FA with a shorter alkyl chain length can stabilize a larger total particle surface area on latex and form smaller particles. The increase in the content of FA leads to increases in δ and particle size, and a decrease in polymerization rate. It may be plausible to consider that the FA has a rather rigid configuration in water. The degree to which the size of monomer droplets can be reduced may be related to the rigidity of the FA