Seeded Emulsion Polymerization Research Articles

Interpretation of interfacial interactions between lenticular particles

Hypothesis: The geometric features of charged particles at a fluid–fluid interface substantially affect their interfacial configurations and interparticle interactions (electrostatic and capillary forces). Because lenticular particles exhibit both spherical and nonspherical surface characteristics, an investigation of their interfacial phenomena can provide in-depth understanding of the relationship between the configuration and the interactions of these particles at the interface.Experiments: Three types of lenticular particles are prepared using a seeded emulsion polymerization method. Pair interactions at the oil–water interface are directly measured with optical laser tweezers. The numerical calculation of the attachment energy of the particle to the interface is used to predict their configuration behaviors at the interface.Findings: The lenticular particles are found to adopt either an upright or inverted configuration that can be determined stochastically. When the interface contacts the truncated boundary or the biconvex boundary, the local interface deformation-induced capillary attraction likely becomes dominant. The contact probability can be estimated on the basis of the attachment energy profile and related to the relative strengths of capillary attraction and electrostatic repulsion between two particles at the interface. Furthermore, possible artifacts in measurements of the pair interactions between nonspherical particles with optical laser tweezers are discussed, depending on their interfacial configurations.

Fabrication of monodisperse asymmetric polystyrene particles by crosslinking regulation in seeded emulsion polymerization

Crosslinking-involved polymerization is a facial and attractive approach to synthesize asymmetric polymer particles despite the great challenge in precisely structure regulation. In the present work, a pre-formed crosslinked shell was intentionally introduced to restrict further polymerization in the seed particles, providing a robust approach for synthesis of asymmetric polymer particles with variations in both surface morphology and overall shape. Systematic experiments were implemented to investigate the role of crosslinker concentration, monomer/seed ration and swelling time in the structure regulation to polystyrene particles. A possible mechanism, in the perspective of crosslinking driven deformation, was proposed to account for the structural evolution of obtained polymer particles during seeded emulsion polymerization, based on which, asymmetric polymer particles with uniform structures of interest from seed particles with different diameters were fabricated.

Synthesis and characterization of core-shell nanoparticles and their application in dental resins

The aim of this study was to synthesize acrylic core-shell particles and silica-loaded core-shell hybrid particles through emulsion polymerization. Also this work examined the influence of synthesized nanoparticles loading in a Bis-GMA/TEGDMA resin matrix on some mechanical properties of the dental composite resins. Core-shell particles consisting of polybutyl acrylate (PBA) rubbery core and polymethyl methacrylate (PMMA)/polystyrene (PS) shell were synthesized by seeded emulsion polymerization. For preparing the core-shell hybrid particles, first silica particles with diameters of about 68 nm were synthesized based on the Stöber process. Then the surface of silica particles was treated with ɣ-MPS. Afterwards, polymeric shell was coated on silica nanoparticles through emulsion polymerization. The morphology of core-shell particles was examined by SEM/TEM. Mechanical properties (fracture toughness, flexural strength and flexural modulus) of the photo-cured Bis-GMA/TEGDMA dental resins/composites filled with different mass fractions of synthesized nanoparticles were tested, and analysis of variance (ANOVA) was used for the statistical analysis of the acquired data. Formation of glassy shell on PBA core in core-shell particles, grafting of ɣ -MPS onto the silica particles and encapsulation of modified silica by polymeric shell in core-shell hybrid particles were confirmed using various analytical techniques. The results of mechanical tests showed that fracture toughness of Bis-GMA/TEGDMA dental resins improved about 35% by the inclusion of 5 wt% silica-loaded core-shell hybrid particles with little effect on flexural strength. This study shows that incorporation of proper amount of hybrid core-shell particles in dental composites can improve their fracture toughness and thus may extend their service life.

Study on Influence of Monobutyl Itaconate and N,N-diethylacrylamide on Acrylic Latex

Polyacrylate latex contained monobutyl itaconate (MBI) and N,N-diethylacrylamide (DEA) was successfully prepared by semi-continuous seeded emulsion polymerization with a green mixed emulsifier of sodium dodecyl benzene sulfonate (SDBS) anion surfactant and tetradecyl hydroxypropyl decyl betaine (THDB) amphoteric emulsifier, the mixed monomers of methyl methacrylate (MMA), butyl acrylate (BA) were modified by MBI and DEA, which were initiated with potassium persulfate (KPS). The structure was characterized by Fourier transform infrared spectroscopy (FTIR). The film of latex was measured by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and contact angle (CA). The particle size of the latex was tested by Zetatrac dynamic light scattering detector. The optimal conditions are as follows: the amount of mixed emulsifiers is 6.0%; the optimum mass ratio of SDBS to THDB is 1 : 1; the amount of initiator is 0.7%; the mass rate of main monomers of MMA : BA = 1 : 1; the amount of DEA is 5.0% and MBI is 2%. In this paper, the polyarcylate emulsion shows excellent thermal stability and hydrophobicity.

Multicolor Electrochromic Dye-Doped Liquid Crystal Yolk-Shell Microcapsules.

A new system of yolk-shell microcapsules containing two types of dye-doped liquid crystals was prepared via seed emulsion polymerization in which the synthetic process was mimicking plant respiration. The resulting system demonstrated reversible low voltage-driven switching between multispectral colored and transparent states. Moreover, wearable multicolor electrochromic fibers based on calcium alginate were produced via wet spinning to expand the application of yolk-shell dye-doped liquid crystal microcapsules. In addition to its long-term optical stability, the proposed cells and fibers also have satisfactory driving voltage values of color change (4.8 and 9.0 V), which are far lower than the human body safety voltage (12 V). We believe that the prepared microcapsules and fibers are potentially widely applicable in smart windows, electronic paper, and military camouflage clothing.

Ghost‐Mirror Approach for Accurate and Efficient Kinetic Monte Carlo Simulation of Seeded Emulsion Polymerization

AbstractThe kinetic Monte Carlo (kMC) method is well suited to the simulation of seeded emulsion polymerization reactions. Inadequate simulation volume results in an incorrect radical entry rate, and as such that inaccuracy propagates into the particle phase simulation. A novel kMC method is described here that has coined the Ghost‐Mirror approach (GM‐kMC) to guarantee sufficient aqueous phase simulation volume while minimizing the number of dispersed phase environments, and while maintaining accuracy and consistency with results produced by kMC simulations. To do so, a subset of a kMC method is replicated where only the aqueous phase reactions are treated in that extended volume; particle phases in those replicated volumes are untreated, as “ghosts”. In doing so, a critical condition for aqueous phase simulation volume is calculated to yield accurate results in the overall system. Important to emphasize though is that one does not require the equivalent number of simulated particles in the GM‐kMC approaches. The required number of particles to simulate accurate results can be even orders of magnitude smaller than the kMC approach; inherently offering significant gains in computational efficiency. This is extended further, reducing the required simulation time, by a hybrid extension to this GM‐kMC method.

Preparation and characterization of fluorine-containing soap-free acrylic emulsion

Purpose Fluorine materials have received the keen attention of many researchers because of their water repellency and low surface free energy. The purpose of this paper is to prepare fluorine-containing soap-free acrylic emulsion, which sodium allyoxypropyl hydroxypropyl sulfonate (COPS-1) and anionic emulsifier sodium a-alkenyl sulfonate (a-AOS) were combined as polymerizable emulsifier, and undecylenic acid (UA) and dodecafluoroheptyl methacrylate(DFMA) were introduced as functional monomer. Design/methodology/approach The fluorinated polyacrylate emulsion was successfully prepared by semi-continuous seed emulsion polymerization, wherein the main monomers were methyl methacrylate (MMA) and butyl methacrylate (BA), and the initiator was potassium persulfate (KPS). Sodium alloxypropyl sulfonate (COPS-1) and an anionic emulsifier sodium a-alkenyl sulfonate (a-AOS) were compounded as a polymerizable emulsifier. Besides, undecylenic acid (UA) and dodecafluoroheptyl methacrylate (DFMA) were introduced as the functional monomers. Findings The optimum recipe of preparing the modified latex is as follows: the amount of emulsifier was 4%, the ratio of emulsifier (COPS-1: AOS) was 3: 1, and the content of initiator was 0.6%. In this case, the conversion rate of acrylic polymer emulsion was high and the polymerization stability was good. When the amount of monomer UA was 2% and the amount of DFMA was 4%, the overall performance of the emulsion was the best. Originality/value The fluorine-containing soap-free acrylic emulsion is prepared via semi-continuous seeded emulsion polymerisation, which sodium allyoxypropyl hydroxypropyl sulfonate (COPS-1) and anionic emulsifier sodium a-alkenyl sulfonate (a-AOS) were combined as polymerizable emulsifier, and undecylenic acid (UA) and dodecafluoroheptyl methacrylate (DFMA) were introduced as functional monomer. There are two main innovations. One is that the fluorine-containing soap-free acrylic emulsion is prepared successfully. The other is that the undecylenic acid is introduced as functional monomer.

Physical properties and morphology of siloxane–polyacrylate dispersion and coating films

The aim of this work was to study the morphology and physical properties of siloxane–polyacrylate (SPA) dispersion and coating films. The SPA dispersion was synthesized by seeded emulsion polymerization using two different types of silane coupling agents, i.e., vinyltriethoxysilane (VTES) and 3-(trimethoxysilyl) propyl methacrylate (MPTMS), at 1–9% by weight. The effect of the type and content of silane coupling agent used in the SPA dispersion synthesis on the resulting morphology and physical properties of the obtained SPA dispersion and coating films were studied. The results revealed that SPA dispersion synthesized using VTES exhibited a smaller particle size and a higher stability than those using MPTMS. Furthermore, the hydrophobic surfaces and water repellence of the coating films using VTES in the emulsion were higher than those using MPTMS, due to the smoother surface morphology.

Preparation and Properties of Nano-ZnO/ Organic Fluorine Modified Polyacrylate Finishing Agent

A nano-ZnO/organic fluorine-modified polyacrylate leather finishing agent was prepared using a mixture of a Silyl-modified nano-ZnO, dodecafluoroheptyl methacrylate (DFMA), methyl methacrylate (MMA) and butyl acrylate (BA) as raw materials. A semi-continuous seeded emulsion polymerization followed. The overall research objective was to improve the bacteriostatic, hydrophobicity and anti-aging properties of leather articles. The structure of the composite emulsion and its film were characterized and analyzed by FT-IR, TEM and XPS. The results showed that the latex particles had an obvious core-shell structure, a smooth surface and were monodisperse. The particle size of the emulsion ranged between 30 and 50 nm. The average value of Zeta potential was -40.1 mV which signified a good emulsion stability. The composite emulsion and its film had good UV resistance and water resistance. When the content of organic fluorine in the film was a maximum 20 %, the contact angle of a water drop on the finished leather, tensile strength and tear strength were 133.48°, 620 N and 61 N, respectively. When the content of nano-ZnO in the film was 1.0%, the average width of antibacterial band of finished leather was 2.1 mm. The finished leather also demonstrated a good anti-aging property.

Biphasic Seeded Emulsion Polymerization in a Tubular Flow Reactor

A novel procedure for the production of polymer latex in a flow tubular reactor capable of achieving high solids content latex (>30 wt %) is reported herein. The novelty of this approach consists o...

New water-based flexographic ink based on new ter-polymer nano-particles as eco-friendly binders – Part II

PurposeThe purpose of this study is to prepare, characterise and evaluate nano-emulsions of ter-polymers of various compositions as eco-friendly binders for flexographic ink industry.Design/methodology/approachVarious nano-emulsions of ter-polymers were prepared based on Vinyl acetate, Vinyl Versatate, butyl acrylate, acrylic acid and acrylamide monomers by means of a conventional seeded emulsion polymerisation technique, using K2S2O8 as the initiator. The characterisation of the prepared emulsions was performed using Fourier transform infrared, thermo-gravimetric analysis, gel permeation chromatography and transmission electron microscopy. A selection of co-polymers and ter-polymers were formulated with pigments and additional ingredients, as water-based flexographic inks. The inks were characterised for their rheological properties, pH, degree of dispersion, water-resistance and colour density.FindingsIt was found that the low viscosity of the prepared polymers may reduce the film thickness of the flexographic inks and may also increase the spreading of the ink on the surface. As a result, stable modified poly acrylate-based latex with improved physico-mechanical properties was obtained. The prepared latexes showed improved properties such as enhanced thermal stability and better water resistance. The effect of the emulsifier type on the properties of the resulting emulsion latexes and their corresponding films were investigated. Also, as the hydrophobic monomer increases, so does the colour density and increasing the binder ratio enhances the gloss values. The improving in gloss values were obtained and provide excellent adhesion properties for both the pigment particles and the base paper.Research limitations/implicationsThe study focusses on the preparation of new water-based ter-polymer nano-particles and their use as eco-friendly binders for flexographic ink industry. Ink formulations based on other different type emulsion polymers could also be studied to assess the applicability of the ink formulation system found for other binders.Practical implicationsThe ink formulations developed could find use in industrial-scale printing.Originality/valueEco-friendly environment and low-cost ink formulations for printing on paper substrates are novel.

Hydrophobic Monomers Recognize Microenvironments in Hydrogel Microspheres during Free‐Radical‐Seeded Emulsion Polymerization

AbstractThe three‐dimensional structure of nanocomposite microgels was precisely determined by cryo‐electron micrography. Several nanocomposite microgels that differ with respect to their nanocomposite structure, which were obtained from seeded emulsion polymerization in the presence of microgels, were used as model nanocomposite materials for cryo‐electron micrography. The obtained three‐dimensional segmentation images of these nanocomposite microgels provide important insights into the interactions between the hydrophobic monomers and the microgels, that is, hydrophobic styrene monomers recognize molecular‐scale differences in polarity within the microgels during the emulsion polymerization. This result led to the formation of unprecedented multi‐layered nanocomposite microgels, which promise substantial potential in colloidal applications.

Hydrophobic Monomers Recognize Microenvironments in Hydrogel Microspheres during Free-Radical-Seeded Emulsion Polymerization.

The three-dimensional structure of nanocomposite microgels was precisely determined by cryo-electron micrography. Several nanocomposite microgels that differ with respect to their nanocomposite structure, which were obtained from seeded emulsion polymerization in the presence of microgels, were used as model nanocomposite materials for cryo-electron micrography. The obtained three-dimensional segmentation images of these nanocomposite microgels provide important insights into the interactions between the hydrophobic monomers and the microgels, that is, hydrophobic styrene monomers recognize molecular-scale differences in polarity within the microgels during the emulsion polymerization. This result led to the formation of unprecedented multi-layered nanocomposite microgels, which promise substantial potential in colloidal applications.

Seed's morphology-induced core-shell composite particles by seeded emulsion polymerization for drug delivery

Cross-liked poly(2-hydroxyethyl methacrylate-co-methacrylic acid) seeds with different morphologies such as cauliflower-like, lobed spherical, and spherical were used in seeded emulsion polymerization (SEP) of 2-(dimethylamino)ethyl methacrylate (DMAEMA), 2-hydroxyethyl methacrylate (HEMA), and methacrylic acid (MAA). The morphological structure of produced composite particles was observed using field emission scanning electron microscopy (FE-SEM). The origin of the formation of different morphologies was discussed using various thermodynamic parameters such as solubility parameters and intermolecular forces between polymeric components involved. Also, the effect of the morphology of seed particles on the resultant structures was investigated. Results showed that morphology of fabricated composite particles is induced from morphology of seed particles with larger sizes. Finally, the fabricated composite particles were utilized in the controlled release of DOX. The effect of morphological changes of synthesized composite particles on the cumulative release behavior at acidic environment indicated the pH-sensitive nature of drug release through carriers. The particles with PDMAEMA shell showed the highest release of DOX at pH = 7.4 whereas PMAA shells displayed the least cumulative release. Inversely, the lowest cumulative release at pH = 1.2 was shown by PDMAEMA-coated carriers. Moreover, particles with spherical morphology had better drug release than cauliflower-like ones originated from smart nature of carriers.

A pH-controlled approach to fabricate electrolyte/non-electrolyte janus particles with low cytotoxicity as carriers of DOX

Seeded emulsion polymerizations of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and methacrylic acid (MAA) were performed in presence of poly(2-hydroxyehtyl methacrylate) (PHEMA) particles as seed to fabricate Janus particles. By tuning the pH value of solution before polymerization, various solutions of protonated and deprotonated monomers were obtained. Then, different morphologies such as core-shell and dumbbell-like were fabricated as a result of pH variations. These composite particles were then used as carriers of DOX in different conditions. All samples showed high loading capacity and long-time release process. Although all morphologies showed insignificant cumulative release at pH = 7.4, release amount was increased to 50–75% at pH = 1. Finally, neat and DOX-loaded particles were introduced to cytotoxicity studies via an MTT assay. According results, PMAA-based particles had no mentionable cell toxicity whereas PDMAEMA-based ones had moderate cytotoxicity. Also, all drug-loaded particles prohibited cell growth significantly. However, DMAEMA-based particles killed more cells than PMAA-based composite particles.

Synthesis of nanoparticles composed of a poly(methylmethacrylate-co-laurylmethacrylate) core and a polysiloxane shell as vehicles for limonene

In this study, hybrid nanoparticles composed of poly(methylmethacrylate-co-laurylmethacrylate) (PMMA-co-LMA) and poly(3-(trimethoxysilyl)propyl methacrylate) (PMS) obtained via seeded emulsion polymerisation were synthesised. A series of copolymers of LMA and MMA was obtained via emulsion polymerisation in the presence of β-cyclodextrin as a phase transport catalyst. The resulting spherical particles of approximately 50 nm were used as seeds for MPS polymerisation, resulting in spherical core-shell particles. These materials were evaluated as vehicles for limonene. Initially, it was observed that the extent of particle swelling by limonene was enhanced at the highest fractions of LMA. The same trend was obtained when the loading capacity and encapsulation efficiency were determined. Although when the core contained PLMA only, the particles exhibited the highest encapsulation capacity, these nanoparticles presented the poorest control on the release of limonene. The cytotoxicity evaluation of the core-shell nanoparticles revealed that they are slightly cytotoxic with cell viabilities higher than 70% at all the concentrations. Our results indicated that core-shell nanoparticles containing a core composed of P(MMA-co-LMA) and a siloxane shell were promising vehicles for nonpolar and volatile compounds, such as limonene, and they showed potential for applications in various fields, such as pest control, food and pharmaceutical industries.

Silicone acrylate dispersion based on semi-continuous seed emulsion polymerization using polymerizable emulsifiers

The silicone modified acrylate dispersion was successfully prepared by semi-continuous seed emulsion polymerization, in which methyl methacrylate (MMA) was used as a hard monomer, butyl methacrylate (BA)was used as a soft monomer, and a double bond-containing polymerizable emulsifier ammonium allyloxtmethylate nonylphenol ethoxylates sulfate (DNS-86)and potassium persulfate (KPS)were utilized as emulsifiers and initiators, respectively. A functional monomer, benzyl methacrylate (BZMA), and a modified monomer, vinyltriethoxysilane (VTES), were introduced into the base dispersion. The factors, which have an influence on emulsion polymerization performance, were optimized. At the same time, the dispersions prepared with conventional emulsifiers and polymerizable emulsifiers were compared under the same conditions. The structure and properties of the synthetic dispersion were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and contact angle (CA). The results showed that the optimum preparation conditions of the dispersion are as follows: The amount of emulsifier was 3%, the amount of initiator was 0.5%, main monomer ratio was 1:1, the amount of functional monomer BZMA and VTES was 3%, respectively. The dispersion obtained by using DNS-86 had better thermal stability, chemical stability and the dispersion was uniformly blue, which represented small particle size. After modification, the film showed higher hydrophobicity.

Preparation, stability and film properties of cationic polyacrylate latex particles with various substituents on the nitrogen atom

Cationic latexes have received wide attention due to their special properties and potential applications in wood coatings, fabric treatment, etc. However, the practical application of cationic latexes was hindered due to their poor stability, especially the alkali resistance stability. In this work, various stable cationic polyacrylate latexes were prepared by an efficient route. Three cationic comonomers, i.e., methacrylatoethyl trimethyl ammonium chloride (DMC), 2-(dimethylamino)ethyl methacrylate (DMAEMA), and 2-aminoethyl methacrylate hydrochloride (AEMH), were used in the aqueous semi-continuous seeded emulsion polymerization of methyl methacrylate (MMA) and butyl acrylate (BA) using cetyl trimethyl ammonium bromide (CTAB) and 2,2′-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (AIBI) as the cationic emulsifier and initiator, respectively. The alkali resistance of the latex could be significantly improved by the addition of cationic monomer DMC and be simply tuned by adjusting DMC dosage. The improved stability of the latex might originate from the higher charge density on the surface of the latex by the introduction of DMC. Moreover, the effects of initiator dosage, emulsifier dosage and different cationic comonomers on the latex preparation and the film properties were also systematically investigated. This work not only introduces an efficient route to prepare cationic latexes with superior stability, but also paves the way for latexes to be used in applications such as textile finishing, paper industry, and biomedical field, etc.

Synthesis and Investigation of Stimuli-Responsive Amphiphilic Latex Nanoparticles by Seeded Emulsion Polymerization

Stimuli-responsive amphiphilic core-shell polymer nanoparticles are an important category of smart materials which have been studied due to their advantages of changing of physical or chemical properties in response of stimuli. In this study, poly[2(dimethylamino)ethyl methacrylate] (PDMAEMA) as hydrophilic core with hydrophobic layer polystyrene (PS) as shell were synthesized by seeded emulsion polymerization to achieve dual-sensitive core-shell nanoparticle (CSNP). Temperature- and CO2- responsive CSNPs were investigated as two important smart behaviors. The CSNPs were characterized by dynamic light scattering (DLS) and scanning electron microscopy (SEM). In addition, two essential parameters including the polymerization conversion and stability of polymer latexes were investigated. Obtained results showed that hydrophilicity-hydrophobicity balance of the latex nanoparticles could be changed by variation of temperature and induction of CO2 gas flow, as a result of temperature- and CO2-responsivities of the PDMAEMA core. The particle size of CSNP was increased when the temperature rised above the lower critical solution temperature (LCST) of the PDMAEMA. It is due to the formation of hydrogen bonds between water molecules and tertiary amine group which lead to swell in PDMAEMA below LCST, and deswelling from water above LCST of the PDMAEMA. Furthermore, the size of the latex nanoparticles was increased from 696 nm to 853 nm after CO2-bubbling which led to increase hydrophilicity or water swelling of PDMAEMA in latex nanoparticles.

Preparation of cationic fluorinated acrylate copolymer latex and its application on cotton fabric

Coupled with the improvement in people’s living standards, the demand for textiles having a special performance like water repellency is mushrooming. In this study, the cationic fluorinated acrylate copolymer latex particles with a core–shell structure were synthesized via semicontinuous seed emulsion polymerization process, using Span 80, Tween 80, and dodecyltrimethylammonium chloride as composite emulsifier and (2-(acryloyloxy)ethyl)trimethylammonium chloride as a cationic monomer. Cationic fluorinated acrylate copolymers were successfully confirmed through the FTIR, 1H NMR, and XPS analyses. In addition, the homogeneous latex particles (~ 132 nm of average size) with an evident core–shell structure were observed by TEM analysis, and a stable positive charge (48 ± 5 mV) on the surface of latex particles was demonstrated by zeta potential analysis. Meanwhile, the results showed that the dosage of dodecafluoroheptyl methacrylate (DFMA) played a vital role in the hydrophobicity of the latex films and the one with the best water repellency was identified with 10 g of DFMA dosage. Furthermore, the cotton fabric finishing experiments demonstrated that, after finishing by the cationic fluorinated acrylate copolymer emulsion, the treated cotton fabric exhibited excellent hydrophobicity even at low concentration, with > 130° of the water contact angle and > 60 min of the static absorbing time.