微米级聚苯乙烯/聚硅氧烷核壳微球的制备、表征及其作为光散射剂的应用

在乙醇/水混合溶剂中采用分散聚合法制备出微米级聚苯乙烯微球,将聚苯乙烯核微球与甲基三甲氧基硅烷的水解溶液混合,加入氨水使硅烷水解产物在核表面缩合交联,制备出微米级聚苯乙烯/聚硅氧烷核壳微球.采用TEM、粒径分布仪、EDX、TG等对核壳微球的形貌、粒径、表面成分和热失重进行了表征.将核壳微球作为光散射剂添加在聚甲基丙烯酸甲酯（PMMA）树脂中,制备出性能良好的光散射材料.当SS6核壳微球的添加浓度为1%（质量）时,制得的PMMA样片（2 mm）的雾度为88.16％,透光率为72.5％;当SS6添加浓度为2%（质量）时,其雾度为92.13％.     

交联型聚硅氧烷/聚丙烯酸酯复合乳胶粒子形态演化的研究

提出了交联体系中复合乳胶粒子的简单演化模型,即链引发→簇生成→簇增长→簇融合→成核。并以聚硅氧烷/聚丙烯酸酯体系为例进行了初步验证。结果表明,复合乳胶粒子的形成过程与假设的演化模型基本吻合。     

Effect of the core/shell latex particle interphase on the mechanical behavior of rubber-toughened poly(methyl methacrylate)

Two- and three-layer composite latex particles were used to prepare rubber-toughened poly(methyl methacrylate) (RT-PMMA). The interfacial thicknesses of the multi-layered particles were varied by using different emulsion polymerization synthesis techniques. The resulting interphases were previously characterized by ¹³C nuclear magnetic resonance techniques. The poly(divinyl benzene)/poly(butyl acrylate) (PDVB/PBA) interphase thickness was found to be in the range of 5–7 nm. It was also found that the PBA/PMMA interphase thickness could be varied from 5 to 7 nm (batch addition of MMA) to 15 to 17 nm (interphase compatibilized with PMMA macromonomer). The interphase thickness was expected to play an important role in the mechanical behavior of PMMA. The effect of the interphase of two- and three-layer particles on the tensile and fracture behavior of PMMA composites was evaluated. The fracture surfaces were examined by scanning electron microscopy. The two-layer PBA/PMMA particles with a thicker interphase (15–17 nm) exhibited higher K_IC values with the PMMA composites compared with PBA/PMMA particles with a thinner interphase (5–7 nm). The three-layer particles were found to be more effective in toughening PMMA compared with the two-layer particles. The differences in toughening behavior are speculated to arise from the morphological effects caused by a thicker interphase, which in turn results in better coverage by the PMMA shell and a more uniform distribution of the toughening particles in the PMMA matrix. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:581–593, 1997     

Studies on the damping performance of polystyrene/polyacrylate latex IPN

Polystyrene/polyacrylate latex IPN (PS/PA LIPN) was synthesized using two-stage emulsion polymerization. The effects of various polymerization parameters on the damping performance were investigated systematically. The results show that the multicomponent copolymerization favours broadening of the damping temperature range. Changing the sequence of adding raw materials and the amount of crosslinker used enables a great improvement in the compatibility of the two networks. Adding inorganic fillers is an important way of increasing and broadening the damping value. Transmission electron micrographs of PS/PA LIPN show the microscopic morphology of LIPN consistent with the above results.     

Structure and property characterization of nanograde core‐shell polyurethane/polyacrylate composite emulsion

Anionic aqueous polyurethane dispersion was synthesized through self‐emulsifing method from cycloaliphatic isophorone diisocyanate (IPDI) and dimethylolpropionic acid (DMPA). The carboxyl acid group in DMPA was used to make the polyurethane dispersible. The polyurethane/polyacrylate (PU/PA) composite particles were also prepared by seeded surfactant‐free emulsion polymerization; the cycloaliphatic polyurethane aqueous dispersion was used as seed particles. The structures and properties of the composite emulsion as well as the physical mixture of polyurethane dispersion and polyacrylate emulsion were characterized by FTIR, DSC, dynamic light scattering, TEM, X‐ray photoelectron spectroscopy (ESCA), and electronic tensile machine. The results showed that the synthesized PU/PA composite emulsion was found to form inverted core‐shell structure with polyacrylate as the core and with polyurethane as the shell, and its diameter of particles is in the range of nanograde, the crosslinking reaction was existed in composite emulsion. The intimate molecular mixing of crosslinking polymers are also claims to result in a superior balance of properties compared to physical blends of polyurethane dispersion and acrylate emulsion. The crosslinking mechanism of PU/PA composite emulsion was also discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of poly(acrylate-styrene)/poly(acrylate-styrene) core/shell latex and TOPEM-DSC characterization

Poly(acrylate-styrene)/poly(acrylate-styrene) core/shell latex particles were synthesized via seeded semi-continuous emulsion polymerization. Both core polymer (CP) and shell polymer (SP) were copolymerized by using three identical monomers of methyl methacrylate (MMA), butyl acrylate (BA) and styrene (St) with different composition ratios. The synthesized core/shell latex particle presents a phase separated state with the interfacial layer between CP and SP. In this study, the weight fractions and the corresponding thickness of this interfacial layer, CP and SP phase in the core/shell latex particle has be successfully calculated by using multi-frequency temperature-modulated differential scanning calorimetry (TOPEM-DSC). The results indicate that the interfacial layer thickness of the core/shell latex particle is determined by the core/shell structure, such as hard core/soft shell (defined as HC/SS) and soft core/hard shell (defined as SC/HS), the glass transition temperature (T_g) of the “hard” phase (correspondingly core or shell for HC/SS or SC/HS structure, respectively), and the existence of hydrophilic monomer during the copolymerization process such as acrylic acid. Meanwhile, the influence of film-formation-temperature on the microstructure of the latex films was systematically explored in this work.     

Glass-transition temperature of a polyacrylate latex film and its water whitening resistance

Polyacrylate latex materials have become a hot area recently in China due to its environmental friendliness. However, the water whitening resistance of the polyacrylate latex products in the market is largely unsatisfactory, which seriously affects the appearance and performance of the latex products. In this work, the effect of glass-transition temperature (T_g) of a polyacrylate latex film on its water whitening resistance was investigated. The light transmittance measurement showed that the higher the T_g of the latex film, the better the water whitening resistance. Atomic force microscope, surface element analysis, static water contact angle measurement, and attenuated total reflection–Fourier transform infrared were used to characterize the accumulation of the emulsifier on the surface of the latex film. It was found that the amount of emulsifier migrated to the surface of the latex film increased with the increase of the T_g of the latex film, that is, the amount of emulsifier remained inside the latex film decreased, thereby reducing its affinity to water. In addition, the higher the T_g of the latex film, the lower the water absorption, also reducing the affinity of the latex film to water. Both work together to improve the water whitening resistance of polyacrylate latex film with higher T_g. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48361.     

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     

Monodisperse core/shell latex particles containing carboxylic acid groups and their optimum acid content for pore generation

Monodisperse seeded latex particles with a core–shell morphology were prepared by copolymerizing, via dropwise addition, styrene (St)–methyl methacrylate (MMA)–acrylic acid (AA) or St–MMA–methacrylic acid (MAA) onto monodisperse seed latex particles of P(St–MMA). The seeded particles thus prepared were subjected to an alkali/acid treatment in order to generate pores in the particles. For the same carboxylic acid content, the volume expansion of the particles due to pore generation was higher in the particles containing AA than in those containing MAA. The size of the pores increased with increasing AA content. However, a maximum particle volume expansion of about 50% was observed for the particles containing 8 mol % AA in the monomer mixture employed in the second stage, and an explanation for this optimum is suggested. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1455–1460, 1999     

Effect of acrylic acid on water-whitening resistance of polyacrylate latex films and its mechanism

Two groups of polyacrylate latexes with higher (21 ~ 35 °C) or lower (−33 ~ −43 °C) glass transition temperatures (T_g) were prepared by adjusting the monomer ratio of butyl acrylate (BA) and styrene (St), and the effect of acrylic acid (AA) on water-whitening resistance of these latex films was investigated. It was found that the water-whitening resistance of the two groups of latex films was different. With the increase of AA content, the water whitening resistance of the latex films with higher T_g continued to improve, while that of the latex films with lower T_g increased first and then decreased. A series of characterizations, such as light transmittance, water whitening, water absorption, static water contact angle, surface morphology, and optical microscope test of the latex film, and so forth, showed that the reason for this difference was that under higher AA content (≥5%), compared with the polyacrylate latex films with lower T_g, the latex films with higher T_g could reach the saturation state of water absorption quickly, and water in these latex films exhibited continuous and large area distribution, rather than formation of many so-called micro- or nano-scale water sacs that can scatter light as found in the latex films with lower T_g.     

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。     

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     

Suspension polymerization of thermally expandable core/shell particles

Acrylonitrile (AN)-methacrylonitrile (MAN) copolymer particles with a core/shell structure were prepared by suspension polymerization. The particles were about 10-20 μm in diameter and had a hollow core containing an inert hydrocarbon. The influence of the monomer feed ratio and the polymerization temperature on the particle morphology was studied. One purpose of this study was to determine the boundaries for achieving a core/shell structure with the polymer encapsulating the hydrocarbon. When polymerizing at 62 °C, it was found that an initial AN/MAN feed ratio (f_AN) between 0.15 and 0.9 results in core/shell particles with encapsulated hydrocarbon. f_AN lower than 0.15 yielded solid particles with no hydrocarbon encapsulated while f_AN higher than 0.9 yielded particles built up entirely from agglomerates of smaller primary particles. In contrast, when polymerizing at 80 °C, a much narrower span of f_AN (0.5-0.85) yielded particles with hydrocarbon encapsulated. The influence on monomer conversion and the molecular weight of the polymer was also studied.     

Synthesis and characterization of PNIPAM/PS core/shell particles

Crosslinked, monodisperse PNIPAM particles were synthesized by precipitation polymerization. The particle size was measured by dynamic light scattering (DLS), capillary hydrodynamic fractionation (CHDF), and transmission electron microscopy (TEM). Two different polymerization methods were used to prepare PNIPAM/PS core/shell particles, both above and below the volume phase transition temperature (VPPT) using either a semibatch or seeded semibatch polymerization process. In both processes, uniform “raspberry” structures were obtained in which polystyrene formed small domains on the surface of the PNIPAM particles. The resulting core and shell structure was confirmed by temperature‐dependent particle size and density gradient experiments. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Factorial experimental design on synthesis of functional core/shell polymeric nanoparticles via differential microemulsion polymerization

Functionalized core/shell nanoparticles of the co‐polymer of methyl methacrylate (MMA) and glycidyl methacrylate (GMA) could be polymerized by differential microemulsion polymerization, using a small amount of surfactant (the weight ratio of sodium dodecyl sulfate (SDS)/monomer is 1 : 24). The core/shell nanoparticles have a high conversion, high molecular weight, and small particle size (25–30 nm). The statistical analysis indicated that SDS, water, and the interactionbetween SDS and water have a significant positive interaction between the MMA conversion to form the core nanoparticles. For the core‐shell polymer, [GMA], [GMA]*[SDS], and [GMA]* [water] have significant negative effects on conversion; whereas [SDS] and [water], [SDS]*[water] and [GMA]*[SDS]*[water] have positive effects on the conversion to form core/shell nanoparticles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

含功能基的核—壳型聚丙烯酸酯乳液的合成与性能

本文以种子乳液聚合法制备了PBA/MMA-MAA核-壳型聚合物,考察了壳层单体MMA和MAA的含量不同时对聚合反应及聚合物其它性能的影响,并用TEM观察了粒子的形态。     

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 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     

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。     

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