Polymeric particles prepared with fluorinated surfmer

Fluoro-containing particles have been obtained by miniemulsion polymerization of styrene and n-butyl methacrylate in presence of fluorinated monomer mono-fluoroalkyl maleate (MFM) which acts as a surfmer providing efficient stability to obtained dispersion and functionalization of particle surface with fluoro-groups. Increase of the MFM concentration in reaction mixture reduces the particle size and dispersions with narrower particle size distribution can be obtained. Blends of fluorinated latexes with styrene-butadiene copolymer latex were examined with regard to formation of low free energy surfaces. It has been shown that blends containing MFM-functionalized polymeric particles possess more hydrophobic surfaces then similar latex films, where particles prepared by polymerization of expensive fluorinated monomer have been applied.     

Polymerization of MMA at the surface of inorganic submicron particles

Inorganic submicron particles, such as TiO₂, were modified with titanate coupling agents. The structure and stability of some titanates, both in solution and at the particle surface, were investigated by various methods. The modified titanium dioxide was dispersed in a solution of sodium dodecylsulphate (SDS) in water. The surfactant adsorbs at the now hydrophobic particle surface, thus creating a micellelike structure with an inorganic particle in the centre. In this system an emulsion polymerization of methyl methacrylate was carried out. Product formed at the particle surface is either physically bound by entanglement or chemically bound by covalent bonding to the titanates. In this way a core-shell morphology is obtained with an inorganic core and a polymer shell. The effects of several reaction parameters on the kinetics of the polymerization were studied. The encapsulated TiO₂ particles may offer interesting prospects in those applications where good coupling between polymer matrix and inorganic particles is necessary, such as latex paints and polymer composite materials.     

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     

Enhanced bondability between inorganic particles and a polysaccharide substrate by encapsulation with regenerated cellulose

Inorganic fillers are widely used in coatings, paints, printing inks, and papermaking. A general problem in such applications is the poor compatibility and weak bondability of the filler with polymeric substrates. Surface modification and encapsulation are common methods adapted to enhance interactions between the filler surface and the substrate. This article presents a bondability improvement between inorganic particles and a polysaccharide substrate by the use of cellulose‐coated, inorganic core–shell nanoparticles. The crystallinity of the coated carbohydrate layer is shown to significantly affect the bondability of the core–shell particles. The impact of the coating layer on the light scattering efficiency has also been studied with theoretical Mie scattering calculations. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Composite magnetic particles: 1. Deposition of magnetite by heterocoagulation method

In this paper we report synthesis and characterization of composite polymeric particles bearing magnetite inclusions and reactive β-diketone groups on the surface. Composites were prepared by two-step method in which first step requires preparation of the functionalized polystyrene core and during second step magnetite was deposited onto core particle surface. This procedure gives a possibility to obtain composite particles with core-shell morphology and both the core size and magnetite shell thickness can be varied. Highly monodisperse PS/AAEM microspheres were synthesized by surfactant-free emulsion polymerization. Change of monomer fleet-ratio gives a possibility to change effectively the final particle size of dispersions without strong changes in particle size distribution. PS/AAEM particles were characterized by light scattering techniques (DLS, SLS) and electron microscopy (SEM) with respect to their particle size and morphology of the surface layer. Magnetite was deposited in form of nano-crystals onto PS-AAEM particle surface by heterocoagulation process. It has been established that more uniform magnetite coating was obtained at lower base amounts used for synthesis of magnetite. Amount of the magnetite on the polymeric particle surface can be effectively controlled by changing the initial FeCl₂ and FeCl₃ concentrations and/or variation of the PS/AAEM core dimensions. It has been confirmed by separation centrifugation technique, that stepwise increase of the magnetite content on the particle surface decrease gradually the stability of colloidal system. Magnetization curves for composite particles indicate that deposited magnetite content is high enough to achieve considerable magnetic response to external magnetic field.     

Synthesis and characteristics of poly(methyl methacrylate-methacrylic acid-3,3-(trimethoxysilyl) propyl methacrylate) hollow latex particles and their application to drug carriers

In this study, the hollow latex particle was synthesized by three processes. The first process was to synthesize the poly(methyl methacrylate-co-methacrylic acid) (poly(MMA-MAA)) copolymer latex particles by the method of soapless emulsion polymerization. Following the first process, the second process was to polymerize MMA, MAA, 3,3-(trimethoxysilyl) propyl methacrylate (MPS), and ethylene glycol dimethacrylate in the presence of poly(MMA-MAA) latex particles to form the linear poly(MMA-MAA)/crosslinking poly(MMA-MAA-MPS) core–shell latex particles. In the third process, the core–shell latex particles were heated in the presence of ammonia to form the poly(MMA-MAA-MPS) hollow latex particles. A sufficient heating time and high-heating temperature were necessary for the ammonia to dissolve the linear poly(MMA-MAA) core to form a perfect hollow structure. The crosslinking poly(MMA-MAA-MPS) shell was a barrier for the ammonia to diffuse into the latex particles so that the latex particle with the high-crosslinking shell showed an imperfect hollow structure. Besides, the hollow 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-MPS)/ZnO composite hollow latex particles. With the increase of crosslinking degree would increase the amount of ZnO bonding. Moreover, the poly(MMA-MAA-MPS) hollow latex particles were used as carriers to load with the model drug, caffeine. The release of caffeine from poly(MMA-MAA-MPS) hollow latex particles was investigated.     

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.     

Amphiphilic particles with hydrophilic core/hydrophobic shell prepared via inverted emulsions

An aqueous solution of acrylamide, its crosslinker (N,N'-methylenebisacrylamide), and an oxidant (ammonium persulfate) was first used to prepare an inverted concentrated emulsion in hexane. Span 80, which is soluble in hexane, was employed as a dispersant. The polymerization of acrylamide in the concentrated emulsion was greatly accelerated by introducing an aqueous solution of a reductant (sodium metabisulfite); it started at room temperature and was completed in a few seconds, resulting in a pastelike product. The system thus obtained was subsequently diluted with hexane containing a hydrophobic monomer. When styrene was used as the hydrophobic monomer, cumene hydroperoxide (which, together with sodium metabisulfite present in the dispersed phase, constitutes the initiator for the polymerization of styrene) was dissolved in the continuous phase. When vinylidene chloride was employed as the hydrophobic monomer, no additional initiator besides sodium metabisulfite and ammonium persulfate already present in the hydrophilic phase had to be employed. The use of initiators which are present only in the hydrophilic phase, and hence also at the interface between this phase and hexane, ensured the polymerization of the hydrophobic monomer as shells that encapsulate the polyacrylamide latexes. Under the proper conditions, a porous outer shell can be generated, which makes the hydrophilic chains present inside accessible. Such hydrophilic core/hydrophobic porous shell particles can be dispersed in water, where they remain stable for a long time, and in hydrophobic liquids, where they remain stable for at least 24 h. For this reason, we call these kinds of particles amphiphilic particles. © 1996 John Wiley & Sons, Inc.     

Core–shell emulsion polymerization of styrene and butyl acrylate in the presence of polymerizable emulsifier

A series of core–shell polymeric particles of styrene butyl acrylate were successfully prepared in the presence of polymerizable emulsifier. The compositions of the emulsions obtained were confirmed by Fourier transformed infrared spectrometry. Latexes and emulsion films were characterized by transmission electron microscopy and scanning electron microscopy, respectively. The thermostability of emulsion films was characterized by thermogravimetric analysis. The results showed that the existence of polymerizable emulsifier could enhance the solid content of the emulsion and the monomer conversion. The optimum mass ratio of polymerizable emulsifier to traditional emulsifier was 1:1, and the polymerizable emulsifier can participate in the emulsion polymerization perfectly. An emulsion with reverse core–shell particles exhibited better hydrophobic properties and thermostability than one with traditional core–shell particles. The film formed by the emulsion with reverse core–shell particles had lower water absorption, and it could be used in the fields of coatings, surface sizing agents, and spinning. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43091.     

Composite polymeric particles with ZnS shells

We report on a preparation of hybrid particles with polymeric cores and ZnS shells. Two types of monodisperse sterically stabilized polystyrene particles with hydroxyl-terminated PEG chains (PS/PEGMA) or β-diketone groups (PS/AAEM) on the surface have been prepared and characterized. Formation of ZnS layer on the surface of submicron particles has been studied by SEM and EDX. Deposition of ZnS on the surface of PS/PEGMA particles is not uniform and leads to formation of ‘raspberry’ morphology with rough surface. It has been found that presence of β-diketone groups on the particle surface leads to formation of well-defined ZnS layers. It has been assumed that such effect is due to the complexation of Zn cations by β-diketone groups leading to nucleation and growth of ZnS crystals on the polymer particle surface. Polymeric particles were completely covered with ZnS if the loaded amount of inorganic material was higher then 40 wt%. The thickness of ZnS layer on the particle surface can be easily varied by changing the ZnS load (in present study maximal thickness of the ZnS shell was 70 nm). It has been found that increase of the ultrasound power leads to considerable increase of the ZnS deposition on the particle surface without strong changes of the particle morphology. Hybrid particles have been investigated with XRD technique and their optical properties were studied by UV-spectroscopy. The colloidal stability of obtained particles was studied by separation analyser. Sedimentation experiments indicate that colloidal stability of obtained composite particles depends strongly on loaded ZnS amount and pH value of the aqueous medium. It has been found that highest sedimentation velocities (or maximum of instability) were determined by ZnS loads, which provide complete coverage of the particle surface. Increase of the ZnS layer thickness led to better stability of hybrid particles in aqueous medium.     

Effect of acrylic core–shell rubber particles on the particulate flow and toughening of PVC

Different types of acrylic core–shell rubber particles with a poly(butyl acrylate) (PBA) core and a grafted poly(methyl methacrylate) (PMMA) shell were synthesized. The average size of acrylic core–shell latex particles ranged from 100 to 170 nm in diameter, having the core gel content in the range of 35–80%. The melt blending behavior of the poly(vinyl chloride) (PVC) and the acrylic core–shell rubber materials having different average particle sizes and gel contents was investigated in a batch mixing process. Although the torque curves showed that the particulate flow of the PVC in the blends was dominant, some differences were observed when the size and gel content of the particles varied. This behavior can be attributed to differences in the plasticizing effect and dispersion state of various types of core–shell rubber particles, which can vary the gelatin process of the PVC in the mixing tool. On the other hand, the highest toughening efficiency was obtained using core–shell rubber particles with the smallest particle size (i.e., 100 nm). The results showed that increasing the gel content of the core–shell impact modifiers with the same particle size improved the particle dispersion state in the PVC matrix. The toughening efficiency decreased for the blends containing 100 and 170 nm rubber particles as the gel content increased. Nevertheless, unexpected behavior was observed for the blends containing 140 nm rubber particles. It was found that a high level of toughness could be achieved if the acrylic core–shell rubber particles as small as 100 nm had a lower gel content. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

聚苯乙烯/无机粒子(核/壳)复合微球的制备与研究进展

综述了近年来国内外聚苯乙烯(PS)/无机粒子(核/壳)复合微球的制备方法,如化学沉积法、静电自组装法和化学镀法等,简述了PS/无机粒子(核/壳)复合微球的优异性能及其应用,展望了PS/无机粒子(核/壳)复合微球的发展前景。     

High dielectric permittivity and low loss in PVDF filled by core-shell Zn@ZnO particles

In this study, metal-semiconductor Zn@ZnO core-shell particles were prepared by the heat treatment of raw Zn powder under air atmosphere, and the prepared Zn@ZnO particles were incorporated into poly(vinylidene fluoride) (PVDF) to obtain high dielectric permittivity polymer. The results indicate that the Zn@ZnO particles remarkably increased the dielectric constant of the PVDF composites compared with the raw Zn/PVDF due to the duplex interfacial polarizations induced by ZnO-Zn interface and ZnO-PVDF interface. Moreover, the dielectric permittivity of the Zn@ZnO/PVDF composites can be further optimized by adjusting the thickness of ZnO shell. The dielectric loss and conductivity were still remained at low acceptable level owing to the presence of ZnO shell between Zn core and PVDF matrix which serves as an interlayer between the Zn cores preventing them from contacting with each other. The developed Zn@ZnO/PVDF polymer composites with high dielectric constant and low loss are potential for embedded capacitor applications.     

Preparation of hydrophobic polymer particles by radical polymerization and subsequent modification into magnetically doped particles

The application potential of hydrophobic polymer is numerous. Lauryl methacrylate (LMA) having long alkyl chain is a commercially available hydrophobic monomer. In this investigation, poly‐LMA (PLMA) latex particles were prepared by suspension polymerization in aqueous media using 2,2′‐azobis(isobutyronitrile) (AIBN) in presence of poly(vinyl alcohol) (PVA) as steric stabilizer. The preparation kinetics was studied in detail in terms of percentage yield and particle size variation. Low glass transition temperature (～ ?65°C) associated with high flexibility did not allow electron micrographic observation though ¹H‐NMR and particle size measurement confirmed the formation of PLMA latex. To improve the glass transition temperature, aqueous emulsion copolymerization of LMA with methyl methacrylate (MMA) was carried out. The solubility of LMA was improved by adding ethanol to the aqueous phase. Two types of polymeric stabilizers, PVA and poly(vinyl pyrrolidone) (PVP) were used to stabilize the colloidal particles. The nature of the stabilizer affected both morphology and final rate of polymerization. The hydrophobic P(LMA‐MMA) copolymer particles were subsequently modified by nanosized magnetic (Fe₃O₄) particles by two different methods. The in situ formation of Fe₃O₄ particles in presence of P(LMA‐MMA) was found to be suitable for the preparation of magnetic latex particles. Scanning electron microscope (SEM), FTIR, transmission electron microscope (TEM), X‐ray diffraction (XRD) and energy‐dispersive X‐ray spectroscopy (EDX) were used for the characterization of magnetically doped particles. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Morphological characterization of attapulgite/poly(methyl methacrylate) particles prepared by soapless emulsion polymerization

BACKGROUND: The synthesis of core–shell inorganic/polymer nanocomposites, in which the polymer shell determines the chemical properties and the interaction with the environment, whereas their physical properties are governed by both the size and shape of the inorganic core and the surrounding organic layer, is an area of increasing research activity. RESULTS: Core–shell and bead–string shaped attapulgite/poly(methyl methacrylate) (ATP/PMMA) nanocomposite particles were prepared by soapless emulsion polymerization in an aqueous suspension of attapulgite organically modified with cetyltrimethylammonium bromide. CONCLUSION: Transmission electron microscopy analysis results showed that the amounts of the monomer added had no influence on the morphologies of the ATP/PMMA particles. The morphologies only depended on the length/diameter ratio of the attapulgite fibrillar single crystal used. Long ATP needles formed the bead–string structure while short ATP needles formed the core–shell structure. Copyright © 2007 Society of Chemical Industry     

Multinuclear core/shell hematite/glass particles for peeling-free red overglaze enamels on porcelain

For red overglaze enamel decoration, a type of colored ceramic coating for ceramics, a partial peeling might occur in mass-produced ceramic ware products. In this study, multinuclear core/shell hematite/glass composite particles, comprising a hematite core and a glass shell, where hematite particles are highly dispersed in a glass matrix, were developed to prepare a red coating material that could achieve a bright red-colored overglaze enamel without peeling. A peeling-free, bright yellowish red-colored overglaze enamel could be obtained when using the composite particles as the red paint. The former function (preventing peeling) can be derived from micrometric size of the shell glass particles and the latter function (high chroma and lightness) is caused by highly dispersive hematite particles in the shell glass particles. Our results suggest that the composite particles are suitable for mass-production due to their peeling-free nature, indicating a potential to be widely used as coloring for ceramic coating products.     

Preparation and characterization of silica/polypyrrole core‐shell colloidal particles in the presence of ethanol as the cosolvent

The silica/polypyrrole core‐shell composites were fabricated by in situ chemical polymerization of pyrrole monomer on the surface of the silica spheres. Silica sol particles with narrow size distributions were prepared by hydrolysis of tetraethoxysilane with sol–gel method. Polypyrrole shell was obtained by chemical polymerization of pyrrole monomer on the surface of the silica spheres in the water–ethanol mixture. It can be seen from the experiment, with the adding of small amount of ethanol cosolvent to the aqueous reaction solution, a uniform coating of polypyrrole appeared on the surface of silica. The core‐shell morphology of composite particles prepared with variation ethanol adding amount was analyzed by TEM. Meanwhile, the conductivity of the core‐shell composite is found to be enhanced apparently compared with those prepared from pure aqueous system. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation of nano-ZnO/PMMA composite particles via grafting of the copolymer onto the surface of zinc oxide nanoparticles

The grafting of polymers onto the surface of zinc oxide nanoparticles and radical copolymerization of methyl methacrylate (MMA) and methacrylic acid (MAA) were investigated. The copolymer chains encapsulating nanoparticles were anchored onto the surface of nano-ZnO through reactions of carboxyl groups with ZnO. Grafting percentage and grafting efficiency of composite particles were investigated by employing thermogravimetric analysis (TGA). FT-IR and ¹³C NMR showed that there existed a strong interaction at the interface of nano-ZnO and copolymer, which implied that the copolymer chains were grafted onto the surface of ZnO nanoparticles. Nano-ZnO being encapsulated by copolymer was confirmed by using transmission electron microscopy (TEM). Additionally, TGA plots showed that the presence of ZnO nanoparticles improved the thermal stability of copolymer to a certain extent. Another important finding is the copolymerization and grafting reaction did not alter the crystalline structure of the ZnO nanoparticles according to the X-ray diffraction patterns. It can also be seen from scanning electron microscope (SEM) that grafted polymer chains on nanoparticles interfere with the aggregation of ZnO nanoparticles in polymer matrix and improve their compatibility with the polymeric matrix.     

Synthesis and characterization of hybrid fluoro‐emulsion based on silica/copolymer composite particles

BACKGROUND: To create a hydrophobic surface, a commonly used two‐step process is the formation of a rough surface and its subsequent modification with materials of low surface energy. Here, a new method for making a hydrophobic surface is proposed using emulsion copolymerization with a low‐surface‐energy fluoropolymer in the presence of a high percentage of silica particles creating a well‐spread roughness. RESULTS: Irregular core–shell structural composite particles such as of snowman shape and sandwich shape were obtained and characterized. The hydrophobicity and chemical structure of the hybrid film were investigated. It was found that strong inter‐ and intramolecular chemical bonding in the composite film may improve the properties of the hybrid film. Enrichment of fluorine on the film surface and well‐distributed roughness due to the silica particles covered by the fluoropolymer contribute to the increased hydrophobicity of the film. The water contact angle on the film increased from 106 ± 2° to 135 ± 2°. CONCLUSION: The stable core–shell hybrid latex synthesized in this work will be of use in preparing high‐performance hydrophobic aqueous coatings. Copyright © 2008 Society of Chemical Industry