Preparation and characterization of trilayer core–shell polysilsesquioxane–fluoroacrylate copolymer composite emulsion particles

Polysilsesquioxane–fluoroacrylate copolymer [poly(methyl methacrylate)–butyl acrylate–dodecafluoroheptyl methacrylate)] (FPSQ) composite latex particles with a trilayer core–shell morphology were manufactured by seeded emulsion polymerization, where PSQ latex particles bearing reactive methacryloxypropyl moieties were first produced by the hydrolysis‐condensation of (3‐methacryloxypropyl)trimethoxysilane, and then they were utilized as seeds, with methyl methacrylate, butyl acrylate, and dodecafluoroheptyl methacrylate as the inner and outer shell monomers. Fourier‐transform infrared spectra and ¹H‐NMR confirm the structure of the FPSQs. Transmission electron microscopy and scanning electron microscopy demonstrate that the obtained composite emulsion particles emerge with the trilayer core–shell pattern. Due to the anchoring of PSQ nanoparticles, the thermal stabilities of the FPSQ films are strengthened, and the resistance to heat is gradually improved along with the increase of the fluoroacrylate dose in the polymer matrix composite. X‐ray photoelectron spectroscopy, atomic force microscopy (AFM), and hydrophobicity investigations indicate that the fluorinated chain segments tend to concentrate at the film–air two‐phase interface. In addition, the AFM result denotes that importing more fluorine into the FPSQ hybrid material will engender greater phase separation and enrichment of the fluoroalkyl segments and a rougher morphology. Thus, the water contact angle of the FPSQ film can ultimately reach 121.4°. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44845.     

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     

Morphology and particle size of nanograde polyurethane/polyacrylate hybrid emulsions

Poly(urethane acrylate) (PUA) composite particles were prepared by seeded surfactant‐free emulsion polymerization. The aqueous polyurethane (PU) dispersions were used as seed particles. The diameters of the seed particles of the aqueous PU dispersions and PUA composite latexes were measured by dynamic light scattering. The microstructures of the PUA composite emulsion particles were observed by transmission electron microscopy. The influences of the amount of the hydrophilic chain extender, the types of initiators, and the PU/polyacrylate (PA) weight ratios on the diameters of the aqueous PU and composite emulsions were also studied. The results showed that the PUA composite emulsions formed a core–shell structure with PU as the shell and with PA as the core. The diameter of the PU seed particles and the particle size of the PUA composite emulsions greatly depended on the amounts of the hydrophilic chain extender used in the preparation of the PU seed; when the hydrophilic chain extender concentration was 7.4%, the average diameter of the PUA composite emulsion particles showed the minimum value. The types of initiators and PU/PA weight ratios did not have a significant influence on the diameter of the PUA composite latex particles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

种子乳液聚合在PUA合成中的应用

系统地概述了种子乳液聚合合成聚氨酯－聚丙烯酸酯（PUA）复合乳液研究的各个方面，包括研究开发背景、基本原理，制备方法和工艺，产物和涂膜的结构和性能等。     

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     

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     

The diacetone acrylamide crosslinking reaction and its control of core‐shell polyacrylate latices at ambient temperature

Self crosslinkable core‐shell polyacrylate latices (PAs) cured at ambient temperature were synthesized by semicontinuous‐seeded emulsion polymerization with diacetone acrylamide (DAAM) and adipic dihydrazide (ADH) as crosslinkable monomers. The influences of DAAM monomer mass content, neutralizer, and curing temperature on the properties of self crosslinkable core‐shell latices and the keto‐hydrazide crosslinking were discussed. The spectroscopic techniques such as Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), atomic force microscopy (AFM), transmission electron microscopy (TEM), and contact angle instruments were used to determine the structure and properties of PAs. The water evaporating rate during the film‐forming process of self crosslinkable core‐shell latices was also investigated. FTIR analyses demonstrate that the keto‐hydrazide crosslinking reaction does not occur in the latex environment but occurs at ambient temperature with the evaporation of water during the film‐forming process. The results of DSC show that the core‐shell crosslinkable PAs have two glass transition temperatures (T_g), and T_gs of crosslinked film are higher than that of non crosslinked fim. Moreover, the keto‐hydrazide reaction is found to be acid catalyzed and favored by the loss of water and the simultaneous decrease in pH arising from the evaporation of ammonia or amines during film‐forming process. Hence, in the volatile ammonia or amines neutralized latices, the latex pH value adjusted to 7–8, which not only ensure the crosslinkable latex with good storage stability but also obtain a coating film with excellent performances by introducing the keto‐hydrazine crosslinking reaction. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation of spherical nanocomposites consisting of silica core and polyacrylate shell by emulsion polymerization

Nanocomposite particles consisting of silica (inorganic core) and polyacrylate (organic shell) were prepared in a form of emulsion by a new and simple method—the emulsion polymerization of acrylic monomers in the presence of silica sol. The key technique of the present emulsion polymerization, which made the formation of the nanocomposites successful, is the usage of nonionic surfactant above its cloud point. The morphology of the composite was investigated by DLS, AFM, and TEM, which clearly showed formation of the core‐shell‐type particles. A transparent film was prepared by casting the emulsion, which showed high resistibility against organic solvents. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 659–669, 2006     

聚氨酯/丙烯酸酯复合乳液的制备方法及性能研究进展

介绍了近年来国内外聚氨酯/丙烯酸酯复合乳液制备方法：物理共混、种子乳液聚合法、原位聚合法等;评述了聚氨酯的结构、聚丙烯酸酯、引发剂以及制备方法等因素对复合乳液性能的影响;对目前常用的无机纳米粒子和交联等对聚氨酯/丙烯酸酯复合乳液改性方法进行了讨论;展望了该领域的发展趋势。     

Molecularly imprinted nanoparticles prepared by core‐shell emulsion polymerization

Submicron core‐shell polymer particles, with molecularly imprinted shells, were prepared by a two‐stage polymerization process. Particles of this type, prepared with a cholesterol‐imprinted ethyleneglycol dimethacrylate shell and in the absence of porogen, were found to be 76 nm in diameter with a surface area of 82 m² g⁻¹. Cholesterol uptake from a 1 mM solution in isohexane was measured at both 10 and 30 mg mL⁻¹, with the imprinted polymer showing considerable binding (up to 57%). Imprinted but not hydrolyzed and hydrolyzed nonimprinted polymers showed very low uptakes (≤4.5%) and a phenol‐imprinted polymer showed reduced binding (36%) under the same conditions. Imprinted shells were also prepared over superparamagnetic polymer cores and over magnetite ferrocolloid alone. The cholesterol binding to magnetic particles was very similar to that of equivalent nonmagnetic materials. Magnetic particles could be sedimented in as little as 30 s in a magnetic field. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1851–1859, 2000     

Nano‐SiO2/PMMA‐PU composite particles with core‐shell structure via emulsion polymerization and their application in epoxy resin

A novel method of nano‐SiO₂/poly(methyl methacrylate)(PMMA)‐polyurethane(PU) composite particles modifying epoxy resin is reported. The composite particles with the obvious core‐shell structure were prepared by emulsion polymerization of PMMA and PU prepolymer on the surface of nano‐SiO₂. The diameter of the composite particles was 50–100 nm with dark core SiO₂ (30–60 nm) and light shell polymer of PMMA and PU (20–30 nm); moreover, PU was well distributed in PMMA with about 10 nm diameter. After nano‐SiO₂ was encapsulated by PMMA and PU, the Si content on the surface decreased rapidly to 2.08% and the N content introduced by PU was about 1.27%. The ratio of polymer to original nano‐SiO₂ (f_p), the grafting ratio of polymer to original nano‐SiO₂ (f_r) and the efficiency grafting ratio of polymer (f_e) were, respectively, about 116.7%, 104.4%, and 89.5%. The as‐prepared composite particles were an effective toughness agent to modify epoxy resin, and the impact strength of the modified epoxy resin increased to 46.64 kJ m^?2 from 19.12 kJ m^?2 of the neat epoxy resin. This research may enrich the field of inorganic nanoparticles with important advances toward the modification for polymer composite materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41919.     

Preparation and surface properties of core‐shell polyacrylate latex containing fluorine and silicon in the shell

The core‐shell polyacrylate latex particles containing fluorine and silicon in the shell were successfully synthesized by a seed emulsion polymerization, using methyl methacrylate (MMA) and butyl acrylate (BA) as main monomers, dodecafluoroheptyl methacrylate (DFMA), and γ‐(methacryloxy) propyltrimethoxy silane (KH‐570) as functional monomers. The influence of the amount of fluorine and silicon monomers on the emulsion polymerization process and the surface properties of the latex films were discussed, and the surface free energy of latex films were estimated using two different theoretical models. The emulsion and its films were characterized by particle size distribution (PSD) analysis, transmission electron microscopy (TEM), Fourier transform infrared spectrum (FTIR), nuclear magnetic resonance (¹H‐NMR and ¹⁹F‐NMR) spectrometry, contact angle (CA) and X‐ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), and thermogravimetry (TG) analysis. The results indicate that the average particle size of the latex particles is about 160 nm and the PSD is narrow, the synthesized latex particles exist with core‐shell structure, and a gradient distribution of fluorine and silicon exist in the latex films. In addition, both the hydrophobicity and thermal stability of the latex films are greatly improved because of the enrichment of fluorine and silicon at the film‐air interface, and the surface free energy is as low as 15.4 mN/m, which is comparable to that of polytetrafluoroethylene (PTFE). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of core‐shell fluoroacrylate copolymer latex via emulsion polymerization and its application in ink‐jet ink

Core‐shell fluoroacrylate copolymer latex was synthesized via semicontinuous seed emulsion polymerization, in which ethyl acrylate was utilized to prepare core, and methyl methacrylate, butyl acrylate, methacrylate acid, and hexafluorobutyl methacrylate were employed to constitute the shell. So the yielded latex particles had the soft core and hard shell. Multifunction and low viscosity of the latex had been applied as the binder of latex inks. The ζ potential showed that the latex particles had high thermodynamic stability. The latex and latex inks exhibited viscosity plateau of Newtonian fluid behaviors. Rheological tests revealed that viscous behaviors dominated in the latex and latex inks. However, there was some interaction among the latex and pigment particles. The hydrophobicity of the cast films of the latex increased with the amount of the fluoroacrylate monomer. Fluorine tended to migrate to the interface between the cast film and air. Therefore, the hydrophobicity was derived from the fluorine enrichment phenomena on the top side of the cast films. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and characterization of core‐shell nanoparticles containing poly(chlorotrifluoroethylene‐co‐ethylvinylether) as core

Core shell latex particles with a glassy core and a low T_g polymeric shell are usually preferred. More so, the glassy core happens to be a fluoropolymer with a shell polymer that helps in processability. We describe here the preparation and characterization of core shell nanoparticles consisting of poly(chlorotrifluoroethylene‐co‐ethylvinylether) as core encapsulated in poly(styrene‐acrylate) copolymer shell using seeded emulsion polymerization method under kinetically controlled monomer starved conditions. Properties of the emulsion using surfactants (fluoro/conventional) and surfactant free conditions were investigated. Average size (100 nm), spherical shape and core–shell morphology of the latex particles was confirmed by dynamic light scattering and transmission electron microscopy. Absence of C? F and C? Cl peaks in X‐ray photoelectron spectroscopy proves that cores are completely covered. Polymerization in the presence of fluorocarbon surfactant was found to give optimum features like narrow size distribution, good shell deposition and no traces of agglomeration. Films of core shell latex particles exhibited improved transparency and enhanced water contact angles thus making them suitable for applications in various fields including coatings. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

核／壳型可遮盖聚合物乳液的研制

采用了种子乳液聚合法,以可被碱溶胀的丙烯酸类聚合物为核,交联型的丙烯酸类高聚物为壳,合成了新型的可以代替部分钛白粉等颜料的可遮盖聚合物。讨论了乳化剂、单体、核壳比等对聚合物性能的影响,其中核壳比在1:15-1:25时,聚合物具有较好的遮盖效果。     

氟代聚丙烯酸酯改性聚氨酯复合乳液的制备及其疏水性

为了提高聚氨酯-丙烯酸酯复合乳液的耐水性和耐溶剂性,将聚氨酯溶液作为反应介质,以丙烯酸十二氟庚酯(FA)和丙烯酸羟丙酯为单体,偶氮二异丁腈为引发剂,在溶液中进行聚丙烯酸酯自由基聚合,然后用N-甲基二乙醇胺进行亲水基扩链,通过溶液聚合相转化法制得新型阳离子氟代聚丙烯酸酯改性聚氨酯复合乳液。通过红外光谱、透射电镜、光电子能谱仪和接触角测定仪分别对复合乳液的结构、乳胶粒形态、膜表面的化学元素组成及疏水性进行了研究。结果表明,含氟链段成功接入了大分子链中,乳液形成稳定的核-壳结构,在膜材料表面形成了主要由含氟丙烯酸酯链段组成的界面,FA的引入可使复合乳液胶膜与水的接触角(PUA膜与水的接触角)由65°提高至98°。     

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     

Kinetic investigations of acrylic–polyurethane composite latex

The effect of various reaction parameters on the rate of polymerization, R_p, and on the particle size and morphology of aqueous acrylic–polyurethane hybrid dispersions, prepared by semibatch emulsion polymerization, was investigated. The particles of polyurethane dispersion were used as seeds during the polymerization of acrylic component: methyl methacrylate (MMA), butyl acrylate (BA), and a mixture of MMA and BA with the ratio of 1:1. These emulsions were found to form structured polymer particles in aqueous media using scanning electron microscopy. The kinetics of the emulsion polymerization was studied on the basis of Wessling's model. The influence of emulsifier and initiator concentrations, including the monomer feed rates, R_m, on the rates of polymerization and on the properties of the resulting dispersions were studied. The number of particles and the particle size were also measured during the polymerization process. The final values were found to be independent of the concentration of the emulsifier, initiator and the monomer feed rate in monomer starved conditions. In the steady‐state conditions, during the seeded semibatch hybrid emulsion polymerization, the rate of polymerization and the monomer feed rate followed the Wessling relationship 1/R_p = 1/K + 1/R_m. The dispersions MMA/PU, BA/PU, and MMA/BA/PU have K values of 0.0441, 0.0419 and 0.0436 mol/min, respectively. The seeded BA/PU hybrid polymerization proceeded according to Smith‐Ewart Case I kinetics, while the MMA/PU hybrid emulsions demonstrate Case II of the Smith‐Ewart kinetic model. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2639–2649, 2002     

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     

Preparation and characterization of titanium dioxide core/polymer shell hybrid composite particles prepared by emulsion polymerization

Titanium dioxide inorganic core and polymer shell composite poly(methyl methacrylate‐co‐butylacrylate‐co‐methacrylic acid) [P(MMA‐co‐BA)‐MAA] particles were prepared by emulsion copolymerization. Fourier transform IR (FTIR) spectroscopy was used to measure the content of MAA composite particles. Dynamic light scattering (DLS) characterized the composite particle size and size distribution. The field emission SEM (FE‐SEM) results of the composite particles showed regular spherical shape and no bare TiO₂ was detected on the whole surface of the samples. The composite particles were produced, showing good spectral reflectance compared with bare TiO₂. TGA results indicated the encapsulation efficiency and estimated density of composite particles. Encapsulation efficiency was up to 78.9% and the density ranged from 1.76 to 1.94 g/cm³. Estimated density of the composite particles is suitable to 1.73 g/cm³, due to density matching with suspending media. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2970–2975, 2004