Preparation of acrylate polymer/silica nanocomposite particles with high silica encapsulation efficiency via miniemulsion polymerization

Acrylate polymer/silica nanocomposite particles were prepared through miniemulsion polymerization by using methyl methacrylate/butyl acrylate mixture containing the well-dispersed nano-sized silica particles coupling treated with 3-(trimethoxysilyl)propyl methacrylate (MPS). The encapsulation efficiency of silica particles was determined through the elution and hydrofluoride acid etching experiments, and the size distribution and the morphology of the composite latex particles were characterized by dynamic light scattering and transmission electron microscopy. The coupling treatment of silica with MPS can improve the encapsulation efficiency of silica and the degree of grafting of polymer onto silica. When 0.10 g MPS/g silica was used to modify silica, the encapsulation efficiency of silica was greater than 95%, and the degree of grafting of acrylate polymer onto silica was about 60%. Although the average size and the size distribution index of the composite latex particles increased as the weight fraction of silica increased, the stable latex containing the ‘guava-like’ composite particles was obtained. The grafting of polymer onto silica particles improved the dispersion of silica particles in the solvents for acrylate polymer and in the polymer matrix.     

Preparation of silica/poly(styrene‐co‐butyl acrylate) core/shell composite particles for absorption of toluene

An absorbent for benzene series with silica/poly(styrene‐co‐butyl acrylate) core/shell structure was prepared via emulsion polymerization. The effects of emulsifier dosage, monomer concentration, and crosslinker dosage on the absorption of the core/shell composite particles were investigated. The composite particles with good absorbency could be obtained when the emulsifier concentration was 2.5 g/L, monomer concentration was 40 g/L, crosslinker dosage was 2.0% (based on the total mass of the monomer), and the initiator dosage was 1.0%. The composite particles exhibited a rapid absorption and the absorption process conformed to the quasi‐second order kinetics. Fourier‐transform infrared spectroscopy, scanning electron microscope, and energy dispersive spectrometer (EDS) showed the presence of copolymer layer on the surface of silica. The work provided a new path to fabricate novel composite absorbent particles for a wide range of applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46172.     

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     

原位乳液聚合制备丙烯腈聚合物/纳米氧化硅复合粒子

利用2,2'-偶氮(2-脒基丙烷)二氯化氢(AIBA)引发剂与纳米氧化硅粒子的静电作用而使AIBA吸附在纳米氧化硅表面,进而引发丙烯腈-甲基丙烯酸甲酯(AN-MMA)原位乳液聚合.考察了AIBA浓度和反应温度对AN-MMA原位乳液聚合动力学的影响以及氧化硅含量对AN-MMA共聚物/纳米氧化硅复合乳胶粒径分布和形态的影响.结果表明:聚合速率随AIBA浓度和聚合温度的升高而增大; AIBA浓度相同时,原位乳液聚合速率小于普通乳液聚合;AN-MMA共聚物/纳米氧化硅复合粒子粒径随纳米氧化硅含量增加而增大;原位乳液聚合得到的复合胶粒表面粗糙,当纳米氧化硅质量分数为10%时,纳米氧化硅与聚合物乳胶粒子复合良好;当纳米氧化硅质量分数为20%和30%时,有部分纳米氧化硅粒子与乳胶粒子分离而分散在连续相中.     

支化型有机硅/丙烯酸酯共聚乳液的合成及其性能

采用种子半连续乳液聚合,以γ-甲基丙烯酰氧基丙基三甲氧基硅烷(MPS)为交联单体,以具有支化型大体积疏水基团的有机硅单体γ-甲基丙烯酰氧基丙基三(三甲基硅氧基)硅烷(MATS)为功能单体,与丙烯酸丁酯和甲基丙烯酸甲酯进行乳液共聚,合成了稳定的交联型高硅含量硅丙乳液。对乳液聚合过程及聚合物膜性能的测试结果表明,随聚合体系中MATS用量由0增加到占单体总质量的10%,乳胶粒子的z-均粒径(Dz)由133.5 nm减小到123.7 nm,粒径多分散指数由1.150减小为1.131;聚合物膜的水表面接触角由61°增大到78,°48 h吸水率由5.9%降低为2.5%。     

MPS-SiO_2/PS核壳型复合粒子的形态与玻璃化转变温度研究

以正硅酸乙酯为原料,调节pH值为碱性,通过溶胶-凝胶工艺制备单分散SiO2球,用偶联剂甲基丙烯酰(3-三甲氧基硅烷)丙酯(MPS)进行改性,得到MPS-SiO2球形粒子。以MPS-SiO2球为种子,苯乙烯为壳单体,乳液聚合法制备核壳结构的MPS-SiO2/PS复合粒子。透射电镜观察复合粒子形态的结果表明,MPS-SiO2球粒径为200 nm左右时,得到覆盆子状核壳结构;MPS-SiO2球粒径为80 nm左右时,得到包含多个MPS-SiO2球的多核壳结构。差示扫描量热法考察MPS-SiO2/PS复合粒子玻璃化转变温度(Tg)的结果表明,随着MPS-SiO2球含量增加,复合粒子的Tg增加;随着MPS-SiO2球粒径减小,复合粒子的Tg也有所增加。     

Effects of mesoporous SBA-15 contents on the properties of polystyrene composites via in-situ emulsion polymerization

Different loading of mesoporous molecular sieve SBA-15 was used to prepare polystyrene (PS)/SBA-15 composite materials via in-situ emulsion polymerization. The influence of SBA-15 silica on the styrene emulsion polymerization was studied regarding to the monomer conversion, particle size and particle size distribution, stability and viscosity of the resulting emulsion. The structure and properties of the composites were investigated by infrared spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and gel permeation chromatography (GPC). In addition, the glass transition temperature (T_g), thermal mechanical property and thermal stability of the composite film were measured by differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA), respectively. The results indicated that the composite emulsion showed high monomer conversion, thick viscosity, low coagulum, uniform particle size and broad size distribution. Molecular weight of the polymer decreased with the increase of mesoporous silica. SBA-15 silica was dispersed evenly in PS matrix at a loading of 5 %. The PS/SBA-15 composite material containing 10 % silica maintained a certain ordered structure. DMA results demonstrated that PS/SBA-15 composite exhibited greater storage modulus and high T_g compared to pure PS. The improved thermal stability and T_g of the composite were also confirmed by the TGA and DSC.     

PMMA/SiO2复合微球在常规乳液体系中的制备及其形态研究

以4-乙烯基吡啶(4-VP)为辅助单体,分别使用十二烷基硫酸钠(SDS)和OP-40(CA897)作乳化剂,在SiO2存在下用常规乳液聚合合成了PMMA/SiO2复合微球.在阴离子乳化剂体系中,通过改变聚合物乳胶粒大小可以得到不同形态的复合微球,在非离子乳化剂体系中,可以得到草莓型或核-壳形态的SiO2/PMMA复合微球,取决于单体滴加速度、乳化剂的浓度和单体/SiO2比.复合微球的形态通过透射电镜及扫描电镜进行表征.     

The surface modification of nanosilica,preparation of nanosilica/acrylic core‐shell composite latex,and its application in toughening PVC matrix

The properties and morphology of nanosilica modified with silane coupling agent, methacryloxypropyltrimethoxysilane (MPS), were characterized by fourier transform infrared, zeta potentials, thermogravimetric analysis, and transmission electron microscopy. The results showed that the grafting ratio of MPS on the surface of nanosilica increased with the MPS content. MPS‐silica/PBA/PMMA core‐shell latexes (MPS‐Si/ACR) were prepared by seeded emulsion polymerization. Then they were used to mix with PVC resin. The outer layer (PMMA) enhanced the dispersibility of MPS‐Si/ACR in the PVC matrix by increasing the interfacial interaction of these composite particles with PVC. The notched impact strengths of the blends were influenced by the weight ratio of MPS to silica, the concentration of emulsifier (SDS), and the MPS‐Si/ACR content. The relationships between the mechanical properties and the core‐shell composite structures were elaborated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Mechanism and grafting reactions in seeded emulsion polymerization with emulsified monomer feeding

The seeded emulsion polymerization of styrene with emulsified monomer feeding was performed by polyethyl acrylate (PEA) latex as seed emulsion. It was shown that the grafting reactions occurred between two components on the composite latex particles. The loci of seeded polymerization were studied by the kinetics of grafting reaction. The highest grafting efficiency in the initial period of seeded emulsion polymerization supported the fact that the surfaces of PEA particles are the sites of polymerization of styrene. The grafting efficiency decreased with increasing monomer‐to‐polymer ratio and initiator concentration. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1495–1499, 1999     

乳液聚合法制备核(二氧化钛)-壳(聚苯乙烯)复合粒子

研究了乳液聚合技术用于聚苯乙烯(polystyrene,PS)包覆改性二氧化钛(TiO2)纳米粒子.十二烷基硫酸钠(sodium dodecyl sulfate,SDS)作乳化剂,考察了其浓度对复合粒子形态的影响.用Fourier红外光谱、透射电镜和热重分析表征了无机-有机核-壳复合粒子.用沉降实验评价复合粒子的分散性和分散稳定性.实验表明:SDS浓度为0.8mg/mL时,可以实现PS对纳米TiO2粒子的成功包覆.最佳条件下,乳液聚合单体转化率达62.0%:包覆效率为54.0%;复合粒子中PS占62.6%;复合粒子平均粒径为181nm.复合粒子能在乙酸乙酯中形成均匀分散体系.     

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     

丙烯酸酯乳液的合成及改性研究

以丙烯酸丁酯(BA)和丙烯酸-2-乙基己酯(2-EHA)为软单体、甲基丙烯酸甲酯(MMA)为硬单体、丙烯酸(AA)为功能单体、甲基丙烯酸羟乙酯(HEMA)为交联单体和十二烷基硫酸钠(SDS)/乳化剂(OP-10)为阴/非离子型复合乳化剂,采用核/壳种子乳液聚合法制备了丙烯酸酯共聚乳液;然后在壳层聚合时寸加入HEMA,并用乙烯基有机硅进行改性,制得硅丙乳液。结果表明:当m(SDS):m(OP-10)=3:2、w(复合乳化剂)=3.4%、w(引发剂)=0.82%、w(HEMA)=3.5%、聚合温度为80℃以及聚合中期加入6.8%乙烯基硅油至壳单体中时,硅丙乳液及其胶膜的稳定性、耐水性和力学性能俱佳。     

聚苯乙烯和聚丙烯酸丁酯无皂核壳乳液聚合反应的研究

聚苯乙烯 (PS)和聚丙烯酸丁酯 (PBA)复合乳液是无皂乳液聚合反应生成的 ,采用丙烯酸丁酯加到聚苯乙烯种子微粒中反应得到的。PS/PBA复合微粒的结构通过红外光谱图明显的吸收峰特征而得到证实。纯PS微粒和低BA含量的PS/PBA微粒几乎是球形和规则的 ,而随着BA单体含量的增加 ,PS/PBA复合微粒的粒子尺寸变大和呈现类似高尔夫球形状。同时 ,本文进一步研究了PS/PBA复合微粒的表面形态学     

Study on emulsion and suspension in situ polymerization

A novel and simple method of emulsion and suspension in situ polymerization was designed for preparing a composite of polystyrene containing core–shell emulsion particles. The advantage of this method was that it did not need a complex process, such as emulsion breaking, washing, drying, and so on, during transforming from emulsion polymerization to suspension polymerization. First, the core–shell particles of poly(styrene/bisphenol A dimethyl methacrylate)/polystyrene [P(St/BPADA)/PS] with crosslinking structure were synthesized by emulsion polymerization. Then the latex was broken with electrolyte dripping and the emulsion particles became swollen and transformed into the monomer in the suspension polymerization system. Thus the emulsion and suspension in situ polymerization could be carried out successfully. The mechanism of the process was investigated in detail. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 404–412, 2005     

Core-shell-structured silica/polyacrylate particles prepared by Pickering emulsion: influence of the nucleation model on particle interfacial organization and emulsion stability

This work reports a new evidence of the versatility of silica sol as a stabilizer for Pickering emulsions. The organization of silica particles at the oil-water interface is a function of the nucleation model. The present results show that nucleation model, together with monomer hydrophobicity, can be used as a trigger to modify the packing density of silica particles at the oil-water interface: Less hydrophobic methylmethacrylate, more wettable with silica particles, favors the formation of core-shell-structured composite when the composite particles are prepared by miniemulsion polymerization in which monomers are fed in batch (droplet nucleation). By contrast, hydrophobic butylacrylate promotes the encapsulating efficiency of silica when monomers are fed dropwise (homogeneous nucleation). The morphologies of polyacrylate-nano-SiO₂ composites prepared from different feed ratio of methylmethacrylate/butylacrylate (with different hydrophobicity) and by different feed processes are characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques. The results from SEM and TEM show that the morphologies of the as-prepared polyacrylate/nano-SiO₂ composite can be a core-shell structure or a bare acrylic sphere. The stability of resulting emulsions composed of these composite particles is strongly dependent on the surface coverage of silica particles. The emulsion stability is improved by densely silica-packed composite particles.     

Effect of acrylic acid and hydroxyethyl methacrylate modified nano-SiO2 particles on poly(methyl methacrylate-hydroxyethyl methacrylate) soap-free emulsion polymerization

Nano-SiO₂ powder was modified with acrylic acid (AA) and hydroxyethyl methacrylate (HEMA), respectively. The kinetics of the soap-free emulsion polymerization of methyl methacrylate (MMA) and HEMA in the presence of unmodified or modified nano-SiO₂ particles was investigated. The structure of the nano-SiO₂ particles and the Poly(MMA-HEMA) composite emulsion was characterized by Fourier transform infrared spectroscope (FT-IR). The particle size and size distribution of the emulsion, the morphology of emulsion particle, the surface tension, and ionic conductivity of these systems before and after polymerization were determined. The IR spectra showed that the organic modifiers were incorporated onto the surface of the nano-particles. In addition, the solid content and monomer conversion of the Poly(MMA-HEMA) composite emulsion with modified nano-SiO₂ are higher than that with original inorganic particles. The particle size became smaller and the particle distribution narrowed after applying the modified nano-SiO₂ particles. The SEM observation demonstrated that the shapes of these emulsion particles were uniform sphere. The surface tension and ionic conductivity increased significantly after polymerization.     

Emulsion polymerization of pentabromobenzyl acrylate: effect of reaction parameters on the produced flame‐retardant nanoparticles

Flame‐retardant nanoparticles of sizes ranging between 33 ± 6 and 460 ± 50 nm were formed by the emulsion polymerization of the pentabromobenzyl acrylate (PBBA) monomer in the presence of sodium dodecyl sulfate as the surfactant and potassium persulfate as the initiator. The effect of various polymerization parameters, e.g. monomer, crosslinker monomer, initiator and surfactant concentrations, on the size, size distribution and polymerization yield of the poly(pentabromobenzyl acrylate) nanoparticles produced has been elucidated. Poly(pentabromobenzyl acrylate)/polystyrene (PPBBA/PS) nanoblends containing 15% and 70% of PPBBA particles of 33 ± 6 and 460 ± 50 nm diameter were prepared by mixing the particles with a PS solution in methylene chloride, followed by evaporation of the methylene chloride from the mixture. The effect of the size and the content of the PPBBA nanoparticles in the nanoblends on the thermal stability of the PS were also elucidated. Copyright © 2011 Society of Chemical Industry     

核壳型复合聚合物乳液合成工艺研究

以乳化单体加料的种子聚合技术,合成了聚丙烯酸乙酯/聚苯乙烯核壳型复合聚合物乳液.确定了种子聚合过程中乳化剂补加量与聚合单体量之间的定量关系和合理的单体加料速率.该体系所得聚台物乳液的乳胶粒是“翻转型”的核壳结构.     

Preparation of polystyrene/poly(methyl methacrylate) core‐shell composite particles by suspension‐emulsion combined polymerization

Suspension‐emulsion combined polymerization process, in which methyl methacrylate (MMA) emulsion polymerization constituents (EPC) were drop wise added to styrene (St) suspension polymerization system, was applied to prepare polystyrene/poly(methyl methacrylate) (PS/PMMA) composite particles. The influences of the feeding condition and the composition of EPC on the particle feature of the resulting composite polymer particles were investigated. It was found that PS/PMMA core‐shell composite particles with a narrow particle size distribution and a great size would be formed when the EPC was added at the viscous energy dominated particle formation stage of St suspension polymerization with a suitable feeding rate, whereas St‐MMA copolymer particles or PS/PMMA composite particles with imperfect core‐shell structure would be formed when the EPC was added at the earlier or later stage of St suspension polymerization, respectively. It was also showed that the EPC composition affected the composite particles formation process. The individual latex particles would exist in the final product when the concentrations of MMA monomer, sodium dodecyl sulfate emulsifier, and potassium persulfate initiator were great in the EPC. Considering the feature of St suspension polymerization and the morphology of PS/PMMA composite particles, the formation mechanism of PS/PMMA particles with core‐shell structure was proposed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009