SYNTHESIS OF BOWL-LIKE PARTICLES BY EMULSION POLYMERIZATION AND RELEASE BEHAVIOR OF SOLVENT FROM THE PARTICLES

1. INTRODUCTION Hollow particles have been produced usually by the alkali swelling procedure (ASP), dynamic swelling method (DSM), and water-in-oil-in-water (w/o/w) emulsion polymerization [1]. Because particles can reserve various chemicals in their hollow, they could be used as reservoir and release material [2]. But almost all the work was to make hollow spheres. One kind of hollow particles, the bowl-shaped polymer particles have some advantages because of their special shape [3~6]…     

Synthesis of Bowl-like Particles by Emulsion Polymerization and Release Behavior of Solvent from the Particles

Bowl-like poly (styrene-co-glycidyl methacrylate) was synthesized by swollen seeded emulsion polymerization. The polymerization was carried out in PS seed emulsion swollen by toluene, whereby the bowl-like particles formed at last. The shape was observed by SEM. These particles became ball-like when swollen by toluene, observed by optical microscope, and the release behavior of solvent from them was examined.     

悬浮-乳液复合聚合聚苯乙烯-聚甲基丙烯酸甲酯复合粒子的颗粒特性和成粒机理

采用在苯乙烯 (St)悬浮聚合过程中滴加甲基丙烯酸甲酯 (MMA)乳液聚合组分的悬浮 乳液复合聚合方法 ,制备大粒径聚苯乙烯 聚甲基丙烯酸甲酯 (PS PMMA)复合粒子 .研究聚合物粒径分布和颗粒形态的变化发现 ,在St悬浮反应中期滴加MMA乳液聚合组分后 ,聚合体系逐渐由悬浮粒子与乳胶粒子并存向形成单峰分布复合粒子转变 ,最终形成核 壳结构完整的大粒径PS PMMA复合粒子 ;在St悬浮反应初期滴加MMA乳液聚合组分 ,St与MMA一起分散成更小液滴 ,反应后期凝并成非核 壳结构复合粒子 ;在St悬浮反应后期滴加MMA乳液聚合组分 ,PMMA乳胶粒子与PS悬浮粒子基本独立存在 .根据以上结果 ,提出了St MMA悬浮 乳液复合聚合的成粒机理 .     

Synthesis of submicron-sized peanut-shaped poly(methyl methacrylate)/polystyrene particles by seeded soap-free emulsion polymerization

Submicron-sized peanut-shaped poly(methyl methacrylate)/polystyrene(PMMA/PS) particles were successfully synthesized by seeded soap-free emulsion polymerization of styrene on the spherical crosslinked PMMA seed particles.The obtained peanut-shaped particles showed a novel internal morphology:PS phase formed one domain which linked to the other domain having PMMA core encased by PS shell.     

苯乙烯-甲基丙烯酸甲酯悬浮-乳液复合聚合过程中聚合物复合粒子组成的变化

采用苯乙烯(St)悬浮聚合过程中滴加甲基丙烯酸甲酯(MMA)乳液聚合组分,悬浮乳液复合聚合(SECP)方法,制备大粒径聚苯乙烯聚甲基丙烯酸甲酯(PS- PMMA)复合粒子.采用FTIR、1H- NMR、13C- NMR分析方法,研究SECP各个时期复合粒子中MMA- St链节摩尔比,发现悬浮粒子中MMA St链节摩尔比逐渐增大,而PMMA乳胶粒子中逐渐减少,表明悬浮相和乳液相间存在物质传递过程.悬浮粒子中MMA链节质量与MMA总投料质量比主要由乳胶粒子生成速率和乳胶粒子向悬浮粒子凝聚速率决定.最终得到的复合粒子除含PS和PMMA均聚物外,还含少量MMA-St共聚物.     

DESIGN AND CONTROL OF SOAP-FREE HYDROPHILIC-HYDROPHOBIC CORE-SHELL LATEX PARTICLES WITH HIGH CARBOXYL CONTENT IN THE CORE OF THE PARTICLES

Soap-free hydrophilic-hydrophobic core-shell latex particles with high carboxyl content in the core of the particles were synthesized via the seeded emulsion polymerization using methyl methacrylate(MMA),butyl acrylate(BA), methacrylic acid(MAA),styrene(St)and ethylene glycol dimethacrylate(EGDMA)as monomers,and the influences of MMA content used in the core preparation on polymerization,particle size and morphology were investigated by transmission electron microscopy,dynamic light scattering and conductometric titration.The results showed that the seeded emulsion polymerization could be carried out smoothly using "starved monomer feeding process" when MAA content in the core preparation was equal to or less than 24 wt%,and the encapsulating efficiency of the hydrophilic P(MMA-BA-MAAEGDMA) core with the hydrophobic PSt shell decreased with the increase in MAA content.When an interlayer of P(MMAMAA -St)with moderate polarity was inserted between the P(MMA-BA-MAA-EGDMA)core and the PSt shell,well designed soap-free hydrophilic-hydrophobic core-shell latex particles with 24 wt%MAA content in the core preparation were obtained.     

The morphology of composite polymer particles produced by multistage soapless seeded emulsion polymerization

 Composite polymer particles which contain poly(methyl methacrylate) (PMMA) and polystyrene (PS) components (PMMA/PS composite particle) were synthesized by the method of multistage soapless seeded emulsion polymerization. In this study, the process of multistage soapless seeded emulsion polymerization included two-stage polymerization, three-stage polymerization or four-stage polymerization. The morphologies of the PMMA/PS composite particles were studied. The kinetic factor was the main force to control the morphology of the linear PMMA–PS composite particles which were synthesized by the method of two-stage reaction. Both the kinetic factor and the thermodynamic factor decide the morphology of the linear composite particles which were synthesized by the method of either three-stage or four-stage reaction. However, the thermodynamic factor cannot influence the morphology of the PMMA/PS composite particles with a cross-linked structure which were synthesized by the method of three-stage reaction. The cross-linked composite polymer particles had the morphology of a multilayer structure, which showed that the polymer layers accumulated in their order of production. Received: 9 January 2001 Accepted: 14 June 2001     

PMMA/PS纳米复合材料的制备及分散相稳定性研究

纳米复合材料具有许多优异的性能,但是由于纳米粒子常常很难以纳米尺寸均匀地分散在基体中,有时即使实现了纳米级分散,在后加工或应用过程中又会发生二次团聚,使得纳米材料的特性不能充分发挥．因此,要获得性能优异的纳米复合材料首先必须解决纳米材料在基体中的均匀、稳定分散问题．     

MICRON CORE-SHELL PARTICLES PREPARED BY GRAFTING POLYMERIZATION OF METHYL METHACRYLATE FROM NARROW DISPERSE SURFACE OF CHLOROMETHYLATED POLYDIVINYLBENZENE VIA ATRP

Grafting of poly(methyl methacrylate) from narrow disperse polymer particles by surface-initiated atom transfer radical polymerization (ATRP) was investigated. Polydivinylbenzene (PDVB) particles were prepared by dispersion polymerization with poly(N-vinyl pyrrolidone) (PVP) as the stabilizer. Chloromethylated PDVB was used as initiating core sites for subsequent ATRP of methyl methacrylate with CuBr/bpy as catalyst system. It was found that poly(methyl methacrylate) was grafted not only from the particle surfaces but also from within a thin shell layer, leading to particles size increases from 2.38-3.00μm with a core-shell structure particles. The grafted core-shell particles were characterized with FTIR, SEM, DSC.     

Effects of surfactants on the morphology of composite polymer particles produced by two‐stage seeded emulsion polymerization

Poly(methyl methacrylate) (PMMA)–polystyrene (PS) composite polymer particles were synthesized in the presence of a surfactant by two‐stage seeded emulsion polymerization. The first stage was the synthesis of PMMA particles by soapless emulsion polymerization; the second stage was the synthesis of the PMMA–PS composite polymer particles with the PMMA particles as seeds. In the second stage of the reaction, three kinds of surfactants—sodium laurate sulfate (SLS), polyoxyethylene (POE) sorbitan monolaurate (Tween 20), and sorbitan monolaurate (Span 20)—were used to synthesize the PMMA–PS composite particles. Both the properties and concentrations of the surfactants influenced the morphology of the composite particles significantly. Core–shell composite particles, with PS as the shell and PMMA as the core, were synthesized in the presence of a low concentration of the hydrophilic surfactant SLS. This result was the same as that in the absence of the surfactant. However, a low concentration of Tween 20 led to composite particles with a core/strawberry‐like shell morphology; the core region was a PS phase, and the strawberry‐like shell was a PS phase dispersed in a PMMA phase. With an increase in the concentration of SLS, the morphology of the composite particles changed from core (PMMA)–shell (PS) to core (PS)–shell (PMMA). Moreover, the effects of a high concentration of Tween 20 or Span 20 on the morphology of the PMMA–PS composite particles were investigated in this study. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2224–2236, 2005     

Formation mechanism of micron-sized monodispersed polymer particles having a hollow structure

 Recently, the authors reported that micron-sized monodispersed cross-linked polymer particles having a single hollow in the inside were produced by seeded polymerization for the dispersion of (toluene/divinylbenzene)-swollen polystyrene (PS) particles prepared utilizing the dynamic swelling method which the authors had proposed. In this article, the particles at various conversions of the seeded polymerization were observed with an optical microscope in detail. From the obtained results, the formation mechanism of the hollow structure is suggested as follows. As seeded polymerization proceeds, poly-divinylbenzene (PDVB) molecules precipitated in the swollen particle are trapped near the interface and gradually pile at the inner surface, which results in a cross-linked PDVB shell. PS which dissolves in the swollen particles is repelled gradually to the inside. After the completion of the polymerization, toluene in the hollow evaporates by drying, and PS clings to the inner wall of the shell uniformly. Received: 14 February 1997 Accepted: 16 April 1997     

ACR-g-PVC复合粒子结构与对PVC的增韧效率

采用丙烯酸丁酯 (BA)和丙烯酸 2 乙基己酯 (EHA)交联共聚物为核 ,BA与EHA或甲基丙烯酸甲酯(MMA)与苯乙烯 (St)或MMA与丙烯酸乙酯 (EA)交联共聚物为壳 ,合成了 3种聚丙烯酸酯 (ACR) [P(BA EHA)、ACRⅠ、ACRⅡ ]胶乳 .以 3种ACR胶乳为种子 ,分别与氯乙烯 (VC)进行乳液接枝共聚 ,制备了相应 3种复合粒子 (ACR g PVC) .借助动态光散射法和透射电镜考察了ACR与复合乳胶粒的粒径与结构 ,表征了所研制材料的形态和冲击韧性 .研究结果表明 ,3种ACR g PVC材料的常温缺口冲击强度随ACR含量增加而显著提高 ,其突跃点的发生具有等橡胶量效应 ,其临界橡胶含量约为 4 % ,并采用脆 韧转变的临界粒子间距模型对其进行了解释 ;P(BA EHA)比核 壳ACRⅠ或ACRⅡ具有更高的增韧效率 ,依据复合粒子的两种理想结构模型对其增韧效率进行了分析 .     

Polar Gradient Latex Particles with Hydrophilic Core and Hydrophobic Shell Prepared via Multistep Emulsion Polymerization

Monodisperse polar gradient particles were synthesized via a three‐step emulsion polymerization using poly(butyl acrylate‐methyl methacrylate‐methacrylic acid‐ethylene glycol dimethacrylate) (P(BA‐MMA‐MAA‐EGDMA)) as core, poly(methyl methacrylate‐methacrylic acid‐styrene) (P(St‐MMA‐MAA)) as interlayer and polystyrene (PSt) as shell. The particle growth and encapsulation in each emulsion polymerization step were followed by transmission electron microscopy (TEM), dynamic light scattering (DLS) and conductometric titration. Results indicated that the feeding mode and the interlayer were essential to prepare the polar gradient latex particles with hydrophilic core and hydrophobic shell. The morphologies of the two‐layer core/interlayer and three‐layer core/interlayer/shell particles were observed in TEM micrographs, and the sequential encapsulations of the carboxyl‐containing core and the core/interlayer particles were confirmed by an increase in the particle size as well as an increase in the buried carboxyl percentage.     

单分散核／壳结构导电高分子复合材料的研究（Ⅰ）——单分散核／壳结构聚苯乙烯／聚吡咯的结构表征

导电高分子在光、电、磁等领域表现出的广泛应用前景 ,使它成为材料科学的研究热点 .然而 ,早期发现的导电高分子的不溶不熔性 ,使它在可加工性和机械性能等方面仍面临许多挑战 .核 /壳结构导电高分子与单分散技术的结合 ,无疑为这一领域的研究带来新的生机和活力 .目前仅有的少量文献主要集中报道微米和亚微米级单分散核 /壳导电高分子复合材料的研究 ,大多采用种子乳液聚合法合成 .微米级的种子乳液通常采用以醇为分散介质的分散聚合方法制备 [1～ 3] ,由于种子分散体系要经反复离心分离 ,除去醇类 ,重新分散在水相中再进行核 /壳导电高分…     

Surface modification of polystyrene latex particles via atom transfer radical polymerization

The atom transfer radical polymerization (ATRP) technique using the copper halide/ N,N′,N′,N″,N″‐pentamethyldiethylenetriamine complex was applied to the graft polymerization of methyl methacrylate and methyl acrylate on the uniform polystyrene (PS) seed particles and formed novel core‐shell particles. The core was submicron crosslinked PS particles that were prepared via emulsifier‐free emulsion polymerization. The crosslinked PS particles obtained were transferred into the organic phase (tetrahydrofuran), and surface modification using the chloromethylation method was performed. Then, the modified seed PS particles were used to initiate ATRP to prepare a controlled poly(methyl methacrylate) (PMMA) and poly(methyl acrylate) (PMA) shell. The final core‐shell particles were characterized using Fourier transform infrared spectroscopy, nuclear magnetic resonance, scanning electron microscopy, thermogravimetric analysis, and elementary analysis. The grafting polymerization was conducted successfully on the surface of modified crosslinked PS particles, and the shell thickness and weight ratio (PMMA and PMA) of the particles were calculated. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 892–900, 2002; DOI 10.1002/pola.10160     

Influence of particle diameter on the morphology of micron-sized, monodispersed composite polymer particles produced by seeded polymerization for the dispersion of highly monomer-swollen polymer particles

 Micron-sized, monodispersed polystyrene (PS)/poly (n-butyl methacrylate) (PBMA) composite particles, in which the PS domain(s) were dispersed in a PBMA continuous phase, were produced by seeded polymerization for dispersions of n-butyl methacrylate (BMA) swollen PS particles in a wide range of PS/BMA ratios in the presence of NaNO₂ as a water-soluble inhibitor. Moreover, in order to change the diameter of the composite particles at same PS/BMA ratio, PS/PBMA (1/150 w/w) composite particles were produced using five kinds of PS particles in a range of diameters from 0.64 to 3.27 μm as seeds. The percentages of the PS/PBMA composite particles having double and triple and over PS domains, which were thermodynamically unstable morphologies, increased with the increase in the diameter of BMA swollen PS particles. There was a clear influence of the size of the swollen particles on the morphology of the PS/PBMA composite particles produced. Received: 30 September 1999/Accepted: 18 April 2000     

亚微米级聚苯乙烯/聚硅氧烷核壳粒子的制备及其应用

以乳液聚合制备的聚苯乙烯乳液为种子,加入甲基三甲氧基硅烷(MTMS)水解溶液进行缩聚反应,合成亚微米级聚苯乙烯/聚硅氧烷核壳粒子,并以此作为光散射剂添加至聚甲基丙烯酸甲酯(PMMA)树脂中,制备了光散射材料;考察了亚微米级核壳粒子添加在PMMA树脂中的分散性。结果表明:经过双螺杆剪切作用的挤出加工后,可以实现核壳粒子在PMMA树脂中的良好分散。核壳粒子可以大幅度提高PMMA的雾度,当聚苯乙烯/聚硅氧烷核壳粒子(NS82)的含量为1%时,制得的PMMA样片(厚度为2 mm)的雾度为89%,透光率为69%,有效光散射系数为61%。     

PU/PSt型复合乳液粒子热力学平衡形态预测

以水性聚氨酯分散液为种子采用无皂乳液聚合新技术合成出了具有核壳结构的聚氨酯 聚苯乙烯(PU PSt)型复合聚合物乳液 .采用界面张力简化计算方法 ,通过界面自由能变化最小的热力学判据对合成的复合乳液粒子的热力学平衡形态进行了预测 .并利用透射电子显微镜和接触角法测定的膜的表面极性对其进行了证实 .结果表明 ,界面自由能变化的最小判据可以推广到PU PSt体系 ,文中给出的界面张力的简化计算方法是可行的 .     

Preparation and Characterization of Polymer Core Shell Latex Particles

Stable core‐shell latex was synthesized by semicontinuous seeded emulsion polymerization with core monomers consisting of styrene (St), butyl acrylate (BA), and shell monomers consisting of methyl methacrylate (MMA), eutyl acrylate (EA), and methacrylic acid (MAA). The effects of compound emulsifier amount, mass ratio of anionic/nonionic emulsifier, and initiator amount on latex performance were investigated. By particle size analysis and transmission electron microscopy (TEM) observation, results suggest that final latex particles have clearly core shell structures.     

Micron-sized monodispersed polymer particles produced by seeded polymerization for the dispersion of high swelling of polymer particles with a large amount of monomer

 Micron-sized monodispersed polystyrene (PS)/poly(n-butyl methacrylate) composite particles were produced as follows. First, 1.77 μm-sized monodispersed PS seed particles produced by dispersion polymerization were dispersed in ethanol/water (1/2, w/w) medium dissolving poly(vinyl alcohol) as a stabilizer. n-Butyl methacrylate (BMA) monomer dissolving benzoyl peroxide initiator was emulsified in ethanol/water (1/2, w/w) solution of sodium dodecyl sulfate as emulsifier with ultrasonic homogenizer, and the BMA monomer emulsion was mixed with the PS seed emulsion. The PS seed particles absorbed with a large amount of BMA (about 150 times weight of the seed particles) for 2 h to about 10 μm in diameter while keeping good monodispersity and BMA droplets disappeared finally. The seeded polymerization was carried out at 70 °C after a certain amount of water was added to depress the redissolving of BMA from the swollen particles into the medium by raising from room temperature to the polymerzation temperature. Received: 21 February 1996 Accepted: 4 September 1996