Synthesis and characterization of poly(fluorinated acrylate)/silica hybrid nanocomposites

The nanocomposite particles (NPs) with inorganic silica as core and fluorinated polymer shell have been in situ synthesized via emulsion polymerization. The chemical composition and core‐shell structure were characterized by Fourier‐transform infrared spectrometry and transmission electron microscopy. The results showed that silica nanoparticles were encapsulated in latex particles, with single‐ and multicore morphologies coexisting. Thermal gravimetric analysis also suggested the successful encapsulation of silica into NPs with enhanced thermal stability. The surface properties of the latex films produced from the core‐shell particles were also investigated by contact angle method and water absorption measurement. Both fluorinated polymer and silica contributed to less water absorption ratio and lower surface‐free energy, which was composed of larger polar component and smaller disperse component, just reversed as usual. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Particle size and morphology of poly[styrene‐co‐(butyl acrylate)]/nano‐silica composite latex

Nanocomposite latex with nano‐silica of varying particle sizes was prepared via in situ polymerization and investigated by submicron particle size analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier‐transform infrared spectrometry (FTIR) and Raman spectrometry. It was found that nanocomposite latex exhibited a core–shell structure with nano‐silica particles enwrapped, resulting in an increase in the latex particle size. The smaller the nano‐silica particles, the more were embedded in each latex particle. The increase in the particle size of latex depended not only on the particle size of nano‐silica, but also on the number of nano‐silica particles in each latex particle. Copyright © 2004 Society of Chemical Industry     

Preparation of polystyrene/poly(vinyl acetate) nanocomposites with a core–shell structure via emulsifier‐free emulsion polymerization

Polystyrene/poly(vinyl acetate) latex nanoparticles with a core–shell morphology in an emulsifier‐free emulsion polymerization system were prepared with purified styrene and vinyl acetate (VAc) as monomers and 2,2′‐azo bis(2‐amino propane) dihydrochloride (ABA,2HCl) as the initiator and emulsifier. The optimized conditions of polymerization of VAc, on top of the already‐formed polystyrene as a core polymer, with a core–shell morphology were obtained using various parameters such as volume ratio of the first and second stages, type of process, and reaction time. The morphologic structure of the nanoparticles was studied by scanning electron microscopy and transmission electron microscopy. The latex nanoparticles and polymers were characterized by differential scanning calorimetry. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2409–2414, 2006     

The preparation of core‐shell CaCO3 particles and its effect on mechanical property of PVC composites

In this study, a novel mechanochemical route to prepare core‐shell structured particles was introduced. XPS, TEM, and dissolving experimental results indicate the formation of [(inorganic particle)/(elastomer)] core‐shell structured particles, and several kinds of calcium carbonate (nano‐CaCO₃) particles with various interfaces were obtained. The mechanical properties and morphological results indicate that the surface treatment of nano‐CaCO₃ particles and the existence of outer elastic layer will strengthen the interfacial interaction between nano‐CaCO₃ particles and PVC matrix, which results in improvement of mechanical properties of PVC/CaCO₃ composites. The theoretical calculations of the interfacial interaction and DMA results confirm these especially when the surface of nano‐CaCO₃ particles was treated by MMA and coated in succession by ACR through vibro‐milling. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1084–1091, 2006     

Preparation of core‐shell latexes for paper coatings

Novel core‐shell latices with a partially crosslinked hydrophilic polymer core and a hard hydrophobic shell of polystyrene were prepared to improve optical properties of coated paper such as gloss and brightness. These core‐shell latices were prepared by sequential addition of a monomer mixture of styrene, n‐butylacrylate and methacrylic acid. Different crosslinkers were used to form the polymer core and in the second stage styrene to form the hard shell component. In addition, attempts were made to further improve optical properties by introducing a new polymerizable optical brightener, i.e., 1‐[(4‐vinylphenoxy)methyl]‐4‐(2‐phenylethylenyl)benzene during polymerization either into the core or into the shell. The prepared core‐shell latex particles were used as specialty plastic pigments for paper coating together with kaolin as the primary pigment. The runability of paper coating formulation by either using a laboratory scale Helicoater or pilot scale JET‐coating machine was very good. The produced coated papers were printed on both sides employing a heat set web offset (HSWO) printer to study the quality of image reproduction in terms of print gloss, print mottle, print through, etc. The core‐shell latices improved the overall print quality. Furthermore, the results demonstrated that by optimizing polymer composition one can significantly enhance the optical properties and surface smoothness of coated paper. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Film formation from pigmented latex systems: Drying kinetics and bulk morphologies of ground calcium carbonate/functionalized poly(n‐butyl methacrylate‐co‐n‐butyl acrylate) blend films

The drying kinetics and bulk morphology of pigmented latex films obtained from poly(n‐butyl methacrylate‐co‐n‐butyl acrylate) latex particles functionalized with carboxyl groups and ground calcium carbonate blends were studied. Latex/pigment blends with higher carboxyl group coverage on the latex particle surfaces dried faster than films with few or no carboxyl groups present. The latex/pigment dispersions also dried faster when there was more stabilizer present in the blend system because of the hydrophilic nature of the stabilizer. The net effect of increasing the pigment volume concentration in the blend system was to shorten the drying time. The bulk morphologies of the freeze‐fractured surfaces of the pigmented latex films were studied with scanning electron microscopy. Scanning electron microscopy analysis showed that increased surface coverage of carboxyl groups on the latex particles in the latex/pigment blends resulted in the formation of smaller pigment aggregates with a more uniform size distribution in the blend films. In addition, the use of smaller latex particles in the blends reduced the ground calcium carbonate pigment aggregate size in the resulting films. Scanning electron microscopy analysis also showed that when the initial stabilizer coverage on the latex particles was equal to 18%, smaller aggregates of ground calcium carbonate were distributed within the copolymer matrix of the blend films in comparison with the cases for which the initial stabilizer coverage on the latex particles was 8 or 36%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2267–2277, 2006     

Synthesis and characterization of nanosilica/polyacrylate composite latex

The nanosilica/polyacrylate organic–inorganic composite latex was synthesized by in‐situ emulsion polymerization of methyl methacrylate (MMA) and butyl acrylate (BA) in the presence of silica nanoparticles, which were modified by silane coupling agent. The surface properties and dispersibility of silica nanoparticles modification, chemical structure, Zeta potential, diameter distribution of the composite latex prepared, surface roughness, and thermal stability of the hybrid film formed by the composite latex were investigated by fourier transform infrared spectrometer (FTIR), transmission electron microscopy (TEM), Zeta meter, ZetaPlus apparatus (dynamic light scattering method), atomic force microscopy (AFM), and thermogravimetric analysis (TGA), respectively. After modification with silane coupling agent, silane was grafted onto the surface of silica nanoparticles to form the organic layers, which was able to efficiently prevent the silica nanoparticles from aggregating to individually homogeneous disperse in the in‐situ emulsion polymerization system and improve the compatibility of silica nanoparticles with the acrylate monomers. The nanosilica/polyacrylate organic–inorganic composite latex prepared had the properties of silica nanoparticles and pure polyacrylate latex but was not simply a combination. Strong chemical bonding tethered the silica and acrylate chains to form the core/shell structural composite latex. Consequently, the hybrid film formed by nanosilica/polyacrylate composite latex exhibited a smooth surface and better thermal properties than the pure polyacrylate film. POLYM. COMPOS. 27:282–288, 2006. © 2006 Society of Plastics Engineers     

Synthesis and characterization of poly(methyl methacrylate–butyl acrylate–acrylic acid)/polyaniline core–shell nanoparticles in miniemulsion media

Conductive polymer particles, polyaniline (PANI)‐coated poly(methyl methacrylate–butyl acrylate–acrylic acid) [P(MMA–BA–AA)] nanoparticles, were prepared. The P(MMA–BA–AA)/PANI core–shell complex particles were synthesized with a two‐step miniemulsion polymerization method with P(MMA–BA–AA) as the core and PANI as the shell. The first step was to prepare the P(MMA–BA–AA) latex particles as the core via miniemulsion polymerization and then to prepare the P(MMA–BA–AA)/PANI core–shell particles. The aniline monomer was added to the mixture of water and core nanoparticles. The aniline monomer could be attracted near the outer surface of the core particles. The polymerization of aniline was started under the action of ammonium persulfate (APS). The final product was the desired core–shell nanoparticles. The morphology of the P(MMA–BA–AA) and P(MMA–BA–AA)/PANI particles was characterized with transmission electron microscopy. The core–shell structure of the P(MMA–BA–AA)/PANI composites was further determined by Fourier transform spectroscopy and ultraviolet–visible measurements. The conductive flakes made from the core–shell latexes were prepared, and the electrical conductivities of the flakes were studied. The highest conductivity of the P(MMA–BA–AA)/PANI pellets was 2.05 S/cm. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and properties of core [poly(styrene‐n‐butyl acrylate)]–shell [poly(styrene–methyl methacrylate–vinyl triethoxide silane)] structured latex particles with self‐crosslinking characteristics

Structured latex particles with a slightly crosslinked poly(styrene‐n‐butyl acrylate) (PSB) core and a poly(styrene–methacrylate–vinyl triethoxide silane) (PSMV) shell were prepared by seed emulsion polymerization, and the latex particle structures were investigated with Fourier transform infrared, thermogravimetric analysis, differential scanning calorimetry, transmission electron microscopy, and dynamic light scattering. The films that were formed from the structured core (PSB)–shell (PSMV) particles under ambient conditions had good water repellency and good tensile strength in comparison with films from structured core (PSB)–shell [poly(styrene–methyl methyacrylate)] latex particles; this was attributed to the self‐crosslinking of CH₂?CH? Si(OCH₂CH₃)₃ in the outer shell structure. The relationship between the particle structure and the film properties was also investigated in this work. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1824–1830, 2006     

Sol–gel process of alkoxysilane in emulsifier‐involved aqueous emulsions: A one‐pot synthetic route to emulsions of core‐shell composite particles and their applications

In this work, a one‐pot route to prepare emulsions of silica/polymer core‐shell composite particles was developed through the direct sol–gel processing of alkoxysilane on the surface of newly synthesized template polymer particles in emulsifier‐involved aqueous emulsions. It included two continuous steps: first, the polymer emulsions were synthesized through emulsion polymerization, and second, the template particles in the emulsions were directly coated with silica via sol–gel reaction of precursors without adding ethanol or removing emulsifiers. The size and morphology of the composite particles were characterized, and the results showed that the silica/polymer composite particles with core‐shell structure could be prepared only on the basis of cationic template emulsions, and the in situ‐coating reaction of sol–gel precursors carried on easier with the increasing of the positive charge density on the surface of template particles. The films formed from the composite emulsions were found to have superior optical and flame‐retardant properties compared to polymer films, owing to the core‐shell composite microstructure of the particles. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Chemical components and properties of core–shell acrylate latex containing fluorine in the shell and their films

Core–shell acrylate latices containing fluorine in the shell were prepared by semicontinuous emulsion polymerization. The chemical components of the latices were determined by Fourier transform infrared, ion‐selective electrode analysis, and differential scanning calorimetry. The average size and morphology of the latex particles were characterized by photocorrelation spectroscopy and transmission electron microscopy, respectively. The latex particles were mainly composed of a non‐fluorine core and a fluorinated shell. The dynamic water contact angles of the latex films from the Wilhelmy method indicated that the latex films containing fluorine in the shell could be wetted by water only with difficulty. The amount of the fluoromonomer played an important role in the modification on the water contact angles, water absorption, and thermal stability of the latex films. In comparison with a random structure, the core–shell structure was more effective for improving the thermal properties of the latex films. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 107–114, 2006     

Silica coated ferrite nanoparticles: Influence of citrate functionalization procedure on final particle morphology

In this paper, magnetic nanoparticles (Fe₃O₄ and NiFe₂O₄) were coated with a biocompatible silica shell via hydrolysis and condensation of tetraethyl orthosilicate (TEOS) by the Stöber process. Magnetic nanoparticles, prepared by chemical co-precipitation from iron and nickel salts, were functionalized with citric acid, in order to provide their deagglomeration and to enable their coating with silica. The parameters of the functionalization procedure were varied (concentration–pH and type of treatment), in order to examine if and how this particular step of preparation affects the final morphology of the core-shell particles. Transmission electron microscopy, zeta potential and particle size measurements revealed that the morphology and the size of obtained core shell particles depend significantly on the core particle size, and thus on the parameters of the functionalization step.     

Preparation of monodispersed hollow polymer particles by seeded emulsion polymerization under low emulsifier conditions

In a low emulsifier system, the MMA‐BA‐MAA copolymer emulsions were prepared as seed latices and the seeded emulsion polymerization of MMA‐MAA‐DVB was consequently carried out to prepare carboxylated core particles. The hydrophobic shell was then synthesized onto the core using styrene, acrylonitrile, and divinylbenzene as comonomers. The hollow latex particles were obtained by alkalization treatment of the core‐shell latex particles. The effects of the feeding rate of monomer mixture, contents of emulsifier SDBS and crosslinking agent DVB, and ratio of the monomers during the core stage and shell stage on the morphology and volume expansion of the latex particles were investigated. The results show that the monodispersed hollow latex particles with large size can be obtained when the feeding rate is 0.1 g/min, SDBS content is 0.15 and 0.2 wt % during the core stage and shell stage, respectively, DVB contents are 1% during the preparation of shell copolymers, and the monomer ratio of the core particle to shell layer is 1 : 8. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1505–1510, 2005     

Preparation and characterization of core–shell polystyrene–polydimethylsiloxane particles by seeded polymerization

Nanometer scale particles of seed latex were successfully prepared by polymerization induced by gamma rays. By modification of the coupling agent 3‐methacryloxylpropyltrimethoxylsilane (MPS) at the surface of polystyrene (PSt) particles, polydimethylsiloxane (PDMS) was introduced outside the PSt particles and composite latex particles with a core–shell (PSt–PDMS) structure were successfully prepared. Because of the chemical bond linkage between the core and the shell, such a structure is stable. Direct evidence of the core–shell structure was observed by transmission electron microscopy (TEM). In addition the chemical bond linkage was confirmed by Fourier‐transfer infrared (FT‐IR) spectroscopy. An indirect proof of the core–shell structure was given by water absorption ratio determination of the different samples. Copyright © 2004 Society of Chemical Industry     

The preparation and characteristics of poly(methyl methacrylate–methylacrylate acid)/nano-ZnO composite latex particles

In this work, poly(methyl methacrylate-co-methylacrylate acid)/ZnO (poly(MMA–MAA)/ZnO) composite latex particle was synthesized by three steps The first step was to synthesize poly(MMA–MAA) copolymer latex particles by soapless emulsion polymerization. Following the first step, the second step was to polymerize MMA, MAA and 3,3-(trimethoxysilyl) propyl methacrylate (MPS) in the presence of poly(MMA–MAA) seed latex particles to form the poly(MMA–MAA)/poly(MMA–MAA–MPS) core–shell latex particles. In the third step, the poly(MMA–MAA)/poly(MMA–MAA–MPS) latex particles reacted with ZnO nanoparticles, which were synthesized by a traditional sol gel method, to form the polymer/inorganic poly(MMA–MAA)/poly(MMA–MAA–MPS)/ZnO composite latex. In this study, MPS with silanol groups essentially was used as the coupling agent to couple with ZnO nanoparticles, while the results of the study showed that there was not covalent bond existed between ZnO particles and polymer latex. The ZnO particles were adsorbed on the surface of polymer latex by electrostatic interaction. Besides, the linear poly(MMA–MAA)/crosslinking poly(MMA–MAA–MPS) core–shell latex particles which were synthesized in the second step were heated in the presence of ammonia to form the hollow poly(MMA–MAA–MPS) latex particles. The factors of heating time and concentration of crosslinking agent significantly influenced the morphology of hollow poly(MMA–MAA–MPS) latex particles.     

Synthesis and characterization of poly(butyl acrylate)/silica and poly(butyl acrylate)/silica/poly(methyl methacrylate) composite particles

Poly(butyl acrylate)/poly(methyl methacrylate) (PBA/PMMA) core–shell particles embedded with nanometer‐sized silica particles were prepared by emulsion polymerization of butyl acrylate (BA) in the presence of silica particles preabsorbed with 2,2′‐azobis(2‐amidinopropane)dihydrochloride (AIBA) initiator and subsequent MMA emulsion polymerization in the presence of PBA/silica composite particles. The morphologies of the resulting PBA/silica and PBA/silica/PMMA composite particles were characterized, which showed that AIBA could be absorbed effectively onto silica particles when the pH of the dispersion medium was greater than the isoelectric potential point of silica. The critical amount of AIBA added to have stable dispersion of silica particles increased as the pH of the dispersion medium increased. PBA/silica composite particles prepared by in situ emulsion polymerization using silica preabsorbed with AIBA showed higher silica absorption efficiency than did the PBA/silica composite particles prepared by direct mixing of PBA latex and silica dispersion or by emulsion polymerization in which AIBA was added after the mixing of BA and silica. The PBA/silica composite particles exhibited a raspberrylike morphology, with silica particles “adhered” to the surfaces of the PBA particles, whereas the PBA/silica/PMMA composite latex particles exhibited a sandwich morphology, with silica particles mainly at the interface between the PBA core and the PMMA shell. Subsequently, the PBA/silica/PMMA composite latex obtained had a narrow particle size distribution and good dispersion stability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3425–3432, 2006     

Synthesis and characterization of poly(butyl acrylate–methyl methacrylate)/polyaniline core–shell latexes

Poly(butyl acrylate–methyl methacrylate) [P(BA–MMA]/polyaniline (PANI) core–shell complex particles were synthesized with a two‐step emulsion polymerization method with P(BA–MMA) as the core and PANI as the shell. The first step was to prepare P(BA–MMA) latex particles as the core via soapless emulsion polymerization. The second step was to prepare P(BA–MMA)/PANI core–shell particles. Sodium dodecyl sulfate was fed into the P(BA–MMA) emulsion as a surfactant, and this was followed by the addition of the aniline monomer. A bilayer structure of the surfactant over the surfaces of the core particles was desired so that the aniline monomer could be attracted near the outer surface of the core particles. In some cases, dodecyl benzene sulfonic acid was added after 2 h when the polymerization of aniline was started. The final product was the desired core–shell particles. The morphology of P(BA–MMA) and P(BA–MMA)/PANI particles was observed with transmission electron microscopy. The thermal properties were studied with thermogravimetric analysis and differential scanning calorimetry. Furthermore, conductive films made from the core–shell latexes were prepared, and the electrical conductivities of the films were studied. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 823–830, 2007     

Interfacial‐initiated seeded emulsion polymerization: preparation of polystyrene/poly(methacrylic acid) core/shell particles in the absence of surfactant

Composite polymer particles with hydrophobic polystyrene (PSt) as the core and hydrophilic poly(methacrylic acid) (PMAA) as the shell were prepared through two‐stage emulsion polymerization without any surfactant. In the first step, narrowly distributed PSt seed particles were prepared by surfactant‐free emulsion polymerization with 2,2′‐azobis(2‐methylpropionamide) dihydrochloride (AMPA) as the initiator. In the second step, hydrophilic PMAA shells were fabricated onto PSt seed particles through redox interfacial‐initiated seeded emulsion polymerization with cumyl hydroperoxide (CHPO)/ferrous sulfate/ethylenediaminetetraacetic acid (EDTA)/sodium formaldehydesulfoxylate (SFS), where the initiation took place mainly at the interface between PSt seed particles and the aqueous medium. The composite particles were characterized with transmission electron microscopy, fourier transform infrared spectroscopy and dynamic light scattering, and the results show that a core/shell structure was successfully built. Hydrodynamic radius (R_h) of the composite particles increased with the amount of polymerized monomers in the seeded emulsion polymerization. Copyright © 2006 Society of Chemical Industry     

Polyacrylate‐core/TiO2‐shell nanocomposite particles prepared by in situ emulsion polymerization

We report the preparation of polyacrylate‐core/TiO₂‐shell nanocomposite particles through in situ emulsion polymerization in the presence of nano‐TiO₂ colloid obtained by the hydrolysis of titanium tetrachloride. The resultant colloidal system can be stable for months without any precipitation. In a typical sample, the diameter of nanocomposite particles was about 150 nm, and the thickness of TiO₂‐shell was 4–10 nm. Only cetyltrimethylammonium bromide was employed to provide the latex particles with positive charge, which was enough for the formation of fine TiO₂ coatings. Three initiators were tested. Ammonia persulfate was the most suitable one, because the cooperative effect was formed by the negatively charged TiO₂ particles and the terminal anionic group (SO₄^2?, the fraction of Ammonia persulfate) of the polymer chain on the surface of latex particles to maintain the stability of nanocomposite system. The pH value played a vital role in obtaining a tight TiO₂ coating. Transmission electron microscopy, X‐ray diffraction and Atomic force microscopy were used to characterize this nanocomposite material. It was found that rutile and anatase coexisted in the nanocomposite film. This may suggest a potential application in the field of photocatalytic coating. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1466–1470, 2006     

Preparation of antireflection coatings with novel cationic–nonionic PU‐SiO2 core–shell particle dispersions

A novel polyurethane (PU)‐SiO₂ core–shell particle dispersion was prepared by an acid‐catalyzed sol–gel process using cationic–nonionic PU particle as template. Results of average sizes, polydispersity index, and transmission electron microscope indicated that tetramethylorthosilicate were first diffused to the surface of PU particles, then occurring hydrolysis–condensation reaction to form core–shell particles. Antireflection coating formulation was prepared by as‐prepared core–shell particle dispersion and SiO₂ sol binder. After dip‐coating in the formulation, antireflection coating was formed on glass surface by calcination. Scanning electron microscopy images showed that pores had been formed inside coating after removing PU template particles, and the coating surface could be almost fully closed. In addition, ultraviolet–visible spectrophotometer analysis showed that the maximum transmittance of antireflection glasses can be as high as 98.6% at 548 nm. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45762.