细乳液聚合制备二氧化钛/聚苯乙烯复合微球及其形貌分析

采用细乳液聚合法,以γ-甲基丙烯酰氧基丙基三甲基硅烷改性的TiO2粒子为核,制备了核壳结构的TiO2/聚苯乙烯(PS)复合微球。研究了超声细乳化时间、乳化剂十二烷基硫酸钠(SDS)的浓度、TiO2用量对细乳液粒径及其分布的影响。通过纳米粒度与Zeta电位分析仪、红外光谱、透射电镜等分析手段对产物进行了表征。结果表明,随着超声细乳化时间的增加,初始液滴的粒径变小。聚合后的乳胶粒粒径随着SDS浓度的增大而减小;TiO2用量不足导致乳胶粒粒径分布变宽,且出现双峰;制备所得的TiO2/PS复合微球粒度分布较为均匀,平均直径为176.5 nm,球形规整度较好。     

Double‐miniemulsion preparation of Fe3O4/poly(methyl methacrylate) magnetic latex

Magnetic poly(methyl methacrylate) (PMMA) microspheres were prepared by double‐miniemulsion polymerization. First, oleic acid coated magnetite particles synthesized by means of coprecipitation were dispersed into octane to obtain a ferrofluid. The ferrofluid and MMA were emulsified to form O/W emulsion, respectively. Subsequently two miniemulsions were mixed together for polymerization. The obtained magnetic polymer particles were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, X‐ray powder diffraction, and thermogravimetry. The results showed that oleic acid coated magnetite particles were well encapsulated in PMMA. The effects of initiator dosage and monomer concentration on the conversion of MMA were also investigated. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Particle morphology development in hybrid miniemulsion polymerization

Incompatibility between polymer phases resulting from hybrid minienulsion polymerization of acrylic monomers in the presence of alkyd resin leads to interesting particle morphologies. In this paper, morphology was deduced through crosscomparison of results from several forms of microscopy. For the combination of methyl methacrylate and alkyd, a derivative of core/shell morphology was observed through the combination of transmission electron microscopy, scanning electron microscopy, and spin diffusion NMR. A raspherry-like shell was found to form on the hybrid particle surface consisting of a full coverage of small (roughly 25 nm) polymethyl methacrylate spheres anchored to the particle surface through grafting with the alkyd core. Migration of the spheres to tha surface is thought to be induced by phase separation, and the size of the spheres precludes their origin from homoparticles from homogeneous nucleation. Homopolymethyl methacrylate particles were also detected in the particle distribution, resulting from the aqueous-phase initiator and hydrophilicity of methyl methacrylate monomer. For copolymer/alkyd systems (either methyl methacrylate/butyl acrylate/acrylic acid/alkyd or methyl methacrylate/butyl acrylate/alkyd), more traditional core/shell morphologies were observed with a lesser degree of homonucleated particles. A significantly different result was found in the combination of butyl acrylate and alkyd, resulting in a continuous particle-phase of polylbutyl acrylate and small internally dispersed island domains of alkyd. This is likely due to the lesser incompatibility between polybutyl acrylate and alkyd along with their similar hydrophobicity and glass transition temperatures. A higher degree of grafting between the alkyd and polybutyl acrylate also contributed to the compatibility between the two components, when compared to hybrid methyl methyl methacrylate/alkyd systems.     

Ultrasonically initiated miniemulsion polymerization of styrene in the presence of Fe3O4 nanoparticles

Ultrasonically initiated miniemulsion polymerization of styrene was conducted in the presence of Fe₃O₄ nanoparticles. Stable polystyrene (PS)/Fe₃O₄ nanocomposite emulsions were prepared and magnetic PS/Fe₃O₄ composite particles were obtained through magnetic separation. The whole procedure comprised two steps. First, Fe₃O₄ nanoparticles were dispersed in the monomer phase with the aid of stabilizer Span‐80. Second, miniemulsion polymerization of styrene in the presence of Fe₃O₄ nanoparticles was carried out under an ultrasonic field in the absence of a chemical initiator. The affecting factors, including stabilizer concentration, surfactant concentration, hexadecane concentration and the amount of Fe₃O₄, were systematically studied. Stabilizer concentration, surfactant concentration and hexadecane concentration strongly affected the formation of the coagulation. The least amount of coagulation was formed at 2.5 wt% Span‐80 concentration. The addition of Fe₃O₄ nanoparticles drastically increased the polymerization rate owing to the fact that Fe₃O₄ nanoparticles increased the acoustic intensity and Fe²⁺ reacted with H₂O₂ to produce hydroxyl radicals and increase the number of radicals. The increase in cosurfactant concentration and power output also increased the polymerization rate. Copyright © 2005 Society of Chemical Industry     

Nanocomposite particles with core‐shell morphology. I. Preparation and characterization of Fe3O4–poly(butyl acrylate‐styrene) particles via miniemulsion polymerization

Colloidal particles with magnetic properties have become increasingly important both technologically and for fundamental studies. Here, chemical initiator‐free miniemulsion polymerization of styrene and butyl acrylate has been performed for preparation of magnetic nanocomposite particles with the diameter of 81–150 nm in the presence of sodium dodecyl sulfate as surfactant, span 80 as stabilizer, and hexadecane as hydrophobe. The polymerization reaction was initiated and progressed under ultrasonic irradiation, generated by immersed probe into the latex. The key point in achievement of encapsulation of modified Fe₃O₄ nanoparticles was preparation of a stable colloidal dispersion at the end of the reaction. The obtained products in each step were characterized by FTIR spectroscopy. Dynamic light scattering analysis was used to follow particle size diameter of the samples. Morphology of the particles and formation of core‐shell structure were analyzed by SEM and TEM micrographs, respectively. TGA and magnetometry of the polymeric films confirmed the extent of insertion of used magnetite and their corresponding behavior. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Superparamagnetic thermoresponsive composite latex via W/O miniemulsion polymerization

In this research, the thermoresponsive composite latex particles were prepared via W/O miniemulsion polymerization. Fe₃O₄ nanoparticles were homogeneously dispersed inside the poly(NIPAAm‐co‐MAA) latex particles. In the first step, PAA oligomers were used as stabilizers to produce a stable water‐based Fe₃O₄ ferrofluid, which could mix well with the water‐soluble monomers. In the second step, the Fe₃O₄/poly(NIPAAm‐co‐MAA) composite latex particles were synthesized via W/O miniemulsion polymerization. This polymerization proceeded in cyclohexane at room temperature, with Span80 as the emulsifier, NIPAAm as the thermoresponsive monomer, MAA as a comonomer with ? COOH functional groups, and APS/SMBS as the redox initiator system. The distribution of Fe₃O₄ nanoparticles inside the composite latex particles was expected to be homogeneous. The nucleation and morphology of the composite latex particles were mainly controlled by the concentration of the surfactant, Span80, in cyclohexane. The properties of the composite latex were examined with several instruments such as DSC and TGA. Finally, the superparamagnetic and thermoresponsive characteristics of this functional composite latex were also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3987–3996, 2006     

Challenges for industrialization of miniemulsion polymerization

Miniemulsion polymerization facilitates the synthesis complex materials that cannot be produced otherwise. These materials have a broad range of potential applications including among others adhesives, coatings, anticounterfeiting, textile pigments, bio-based polymer dispersions, gene and drug delivery, anti-viral therapy, tissue engineering, catalyst supports, polymeric photoresists, energy storage and self-healing agents. However, 40 years after the pioneering work of Ugelstad, El-Aasser and Vanderhoff the promises have not been fulfilled and the presence of miniemulsion polymerization in commercial products is scarce. This article reviews the advances in the field, discusses the reasons for this delay and analyzes the challenges that have to be overcome in order to fully use this process in commercial practice.     

Synthesis of Fe3O4/PMMA composite latex particles: Kinetic modeling

In this work, a generalized mathematical model was developed to estimate the variation of particle concentration during the entire course of soapless emulsion polymerization of methyl methacrylate with ferrofluid. Two mechanisms for the nucleation and growth of particles throughout the polymerization reaction were discussed: Mechanism I – seeded polymerization; and Mechanism II – self‐nucleation polymerization. Here, the self‐nucleation included homogeneous nucleation and micelle nucleation. Coagulation between particles, which came from different nucleation mechanisms during the course of polymerization, was considered and included in this model. When appropriate parameters were selected, this model could be successfully used to interpret the variation of particle concentration during the entire reaction. Under different conditions, rate of polymerization, number of radicals in each particle, average molecular weight of polymers, and rate constant of termination were also calculated. All of them explained the experimental results quite well. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4925–4934, 2006     

The formation of asymmetric polystyrene/saponite composite nanoparticles via miniemulsion polymerization

The synthesis of asymmetric spherical nanoparticles has attracted great interest because their anisotropic structure can be used as unique building blocks for constructing advanced materials. In this article, we report the formation of hemispherical or truncated polystyrene/nanosaponite composite particles via one‐pot miniemulsion polymerization. It was found that the morphology of final composite latex particles strongly depends on the size of the nanoclay and its surface properties. Hemisphere or truncated sphere is the dominant morphology if the size of the nanoclay is larger than 100 nm. With the increase of the nanoclay content (up to 30 wt %), the fraction of hemispherical or truncated polystyrene/nanosaponite composite latex particles increased accordingly. The formation of hemispherical particles is possibly attributed to either the asymmetric growth of polymer chains on one side of the hydrophobically modified clay or the mechanical peeling‐off of large spherical particles between polymer and saponite. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

细乳液聚合制备有机硅/丙烯酸酯乳液及其性能

利用细乳液聚合技术设计并制备了不同有机硅含量的有机硅改性丙烯酸酯共聚物稳定乳液.通过细乳液共聚合反应在丙烯酸酯类聚合物主链上引入硅氧烷侧基,该基团水解后与羟基硅油缩合,引入聚硅氧烷接枝链.研究表明：（1）γ-甲基丙烯酰氧丙基三甲氧基硅烷(MPMS)比乙烯基三乙氧基硅烷(VTES)更适合在本体系中用作共聚有机硅单体;（2）聚合过程中,乳液稳定,凝聚物很少;（3）羟基硅油能较好地接枝到丙烯酸酯聚合物主链上,接枝率在50%左右;（4）有机硅的引入减少聚合物涂层的吸水率,表面的水接触角也明显增大,显示出较强的疏水特性.有机硅含量在10%（质量）时,聚合物涂层即可显示很好的憎水特性,随着有机硅含量进一步提高,憎水特性可进一步提高,聚合物涂膜吸水率可低至5%,水接触角可高达105°.     

Particle nucleation and growth mechanisms in miniemulsion polymerization of styrene

Styrene miniemulsion polymerizations stabilized by sodium lauryl sulfate in combination with a reactive costabilizer, lauryl methacrylate (LMA) or stearyl methacrylate (SMA), were studied. A small amount of extremely hydrophobic dye was incorporated into monomer droplets (10² nm in diameter) to investigate particle nucleation and growth mechanisms. In addition to monomer droplet nucleation, particle nuclei generated in the aqueous phase (homogeneous nucleation) also play an important role in both LMA‐ and SMA‐containing polymerization systems. The way that these two nucleation mechanisms compete with each other is closely related to the water solubility of the costabilizer (LMA > SMA). The fraction of latex particles originating from homogeneous nucleation increases with decreasing hydrophobicity of the costabilizer. Zeta potential data of latex particles and the molecular weight and molecular weight distribution of emulsion polymers provide supporting evidence for the proposed competitive particle nucleation and growth mechanisms. © 2002 Society of Chemical Industry     

Elucidation of the miniemulsion stabilization mechanism and polymerization kinetics

Styrene/hexadecane miniemulsions were polymerized at 50°C using a redox initiator. The miniemulsions and their corresponding latexes were characterized in terms of size, polymerization rate, and surface properties. The resulting data were analyzed to elucidate the miniemulsion stabilization and polymerization mechanisms. It was found that the free surfactant concentration exceeded the critical micelle concentration when large amounts of surfactant (60 mM sodium lauryl sulfate) were used, resulting in simultaneous micellar and droplet nucleation. Most surfactant was on the surface of the droplets (85%) or particles (95%). The fractional surface coverage was proportional to the surfactant concentration to the 0.55 power. Using a particle diameter equation, the number of particles was calculated to be proportional to the surfactant concentration to the 1.35 power. Through direct particle size measurements, a power of 1.38 was confirmed. The rate of polymerization was determined by reaction calorimetry to be proportional to the number of particles to the 0.59 power, in contrast to classical Smith–Ewart kinetics for conventional emulsions (1.0 power). The average number of radicals per particle was estimated from the rate and number data, and varied with the particle diameter to the 0.97 power. The observed kinetic dependencies were validated through an extension of Smith–Ewart theory. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3987–3993, 2003     

Mechanism of seeded dispersion polymerization of methyl methacrylate using submicron polystyrene seed particles

Submicron polystyrene (PS) latex particles were used as seed in seeded dispersion polymerization of methyl methacrylate (MMA) to investigate the particle nucleation and aggregation behavior in this type of polymerization. The PS seed particles were located and tracked during the reaction using a refractive index matching technique. The number of PS seed particles present in the poly(methyl methacrylate) (PMMA) particles was investigated in detail throughout the reaction. The change in the distribution of PMMA particle populations containing different numbers of seed particles indicated that intensive nucleation and aggregation occurred during the early stage of the reaction until a transition point of 8.7% conversion was attained under the reaction conditions studied. The size of the large particles at this point was around 1 μm. These particles were regarded as mature particles that did not aggregate with other mature particles. Meanwhile, immature particle were still generated continuously from the continuous phase. These immature particles could not survive the aggregation process to grow to become mature particle, but instead, were captured by the mature particles. Therefore, the total number of the mature particles remained constant from this point until the end of the reaction. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

细乳液聚合法制备PY-17/PE蜡/PS复合乳胶粒子

通过细乳液聚合法制备彩色墨粉用多组分复合乳胶粒子,即通过细乳液聚合法制备聚苯乙烯包覆有机颜料PY-17和聚乙烯蜡的三元复合乳胶粒子。通过透射电子显微镜、激光粒度仪、紫外可见分光光度计和热失重分析仪对制备的复合乳胶粒子形貌、粒度、热学和光学特性进行表征,着重研究了乳化剂种类及用量、颜料用量和聚乙烯蜡用量对复合乳胶粒子粒径和形貌的影响,并对复合乳胶粒子的热学及光学特性进行了表征。结果表明,使用复合乳化剂,颜料PY-17用量不大于单体量8%、聚乙烯蜡用量占单体量不大于10%时,制备的复合乳胶粒子粒径较小,分布窄,包覆较为完整;并且复合乳胶粒子的热学及光学特性发生了一定的改变。     

微小乳液聚合制备丙烯酸酯杂化聚氨酯分散液

微小乳液聚合工艺技术在25~30年前即已问世,但用于丙烯酸酯杂化聚氨酯分散液的制备仅有10年历史。用该工艺技术可有效制得稳定的纳米级丙烯酸酯杂化聚氨酯分散液,其性能独特。本文阐述了微小乳液聚合工艺的原理、影响因素、存在问题和解决措施,并以实例说明之。     

Synthesis of polypyrrole/indium tin oxide nanocomposites via miniemulsion polymerization

Polypyrrole/indium tin oxide nanocomposites were synthesized via in situ miniemulsion polymerization of pyrrole monomer in the presence of indium tin oxide nanoparticles. Different nanocomposites were synthesized by different loadings of nano indium tin oxide. The morphology and nanoparticles distribution of the nanocomposites were characterized by electron microscopy. The results of XRD and TEM analysis showed that indium tin oxide nanoparticles were well placed in the polymeric structure of latex. FTIR analysis was used for the characterization of synthesized polypyrrole and its nanocomposites. TGA analysis was performed to investigate the thermal behavior of pristine polypyrrole and its nanocomposites. Conductivities of nanocomposites were measured by 4-point probe method and compared to the neat polymer.     

微滴乳液聚合制备PDMS/SiO2纳米复合材料

采用超声分散的方法,以少量八甲基环四硅氧烷(D₄)对硅溶胶粒子进行表面接枝改性。然后在改性硅溶胶存在下,以十二烷基苯磺酸(DBSA)为乳化剂兼催化剂进行D₄的微滴乳液聚合,得到聚硅氧烷(PDMS)/二氧化硅(SiO₂)纳米复合乳液。采用FTIR、TGA、纳米粒度仪、TEM和拉力机分别对样品进行了表征。结果表明:采用超声分散的方法,能够有效地实现硅溶胶粒子的表面改性。通过微滴乳液聚合得到的复合乳胶粒是聚合物包覆二氧化硅粒子的核壳结构形态。SiO₂的引入提高了有机硅复合膜力学性能,增强了热稳定性。     

Fe3O4/P(St/ACPA)磁性高分子纳米球的制备与磁性能研究

采用化学共沉淀方法制备Fe_3O_4磁性粒子,并使用油酸和十一烯酸对其进行表面改性,然后采用一步细乳液聚合法制备含有羧基官能团的Fe_3O_4/P(St/ACPA)磁性高分子纳米球,对磁流体和磁性高分子纳米球进行性能表征。结果表明,改性的Fe_3O_4磁流体分散性好,粒径均一,在室温下呈超顺磁性,磁含量为68.5%(w),饱和磁化强度为51.3emu/g;Fe_3O_4/P(St/ACPA)磁性高分子纳米球成球性好,粒径为70 nm,磁含量为39%(w),饱和磁化强度为27.9 emu/g。     

Emulsifier‐free miniemulsion polymerization of styrene and the investigation of encapsulation of nanoparticles with polystyrene via this procedure using an anionic initiator

Emulsifier‐free miniemulsion polymerization of styrene was investigated in the presence of potassium persulfate (KPS) as an anionic initiator and cetyl alcohol as a costabilizer using ultrasonic irradiation and comparison of this procedure with conventional emulsifier‐free emulsion polymerization showed that this method has a remarkably higher polymerization rate (R_p), smaller size of particles, and narrower molecular weight distribution via gravimetric measurement, transmission electron microscopy (TEM), and gel permeation chromatography techniques, respectively. Then, the encapsulation of magnetite (Fe₃O₄) and titanium dioxide (TiO₂) nanoparticles with polystyrene was investigated using this procedure. Attempt to encapsulate magnetite nanoparticles failed; however, the encapsulation of titanium dioxide nanoparticles was successfully carried out via this procedure using KPS in both cases. TEM proved the presence of TiO₂ nanoparticles in polymer particles, and thermogravimetric analysis was used to determine the percentage of TiO₂ in the products. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

IBN partition between st monomer/polymer and water and its application in miniemulsion polymerization initiated by AIBN

Isobutyronitrile has been selected as a stable substitute for the 2‐cyano‐2‐propyl radical originating from 2,2′‐azobis(isobutyronitrile) to study the behavior of this radical in miniemulsion polymerization. The partition of isobutyronitrile between styrene monomers/polymers and water has been investigated by carrying out equilibrium experiments under different conditions. Prediction based on a published kinetic model using the newly measured partition coefficient has also been compared with published experimental data and prediction based on the partition coefficient of 2,2′‐azobis(isobutyronitrile). The partition coefficients for isobutyronitrile were found to be 10.98 for the styrene/water system and 4.34 for the polystyrene/water system, respectively. The partition coefficient was found to be unaffected by selected conditions. The model prediction based on the partition coefficient of isobutyronitrile agreed well with the published experimental data, thus, indicating that the partition coefficient of the primary radical should be used in theoretical calculations rather than that of the initiator. © 2011 American Institute of Chemical Engineers AIChE J, 58: 3135–3143, 2012