Production of micron-sized, monodispersed, multilayered composite polymer particles by multistep seeded dispersion polymerization

 Micron-sized, monodispersed, poly(methyl methacrylate) (PMMA)/polystyrene (PS)/PMMA/PS multilayered composite particles were successfully produced by three-step seeded dispersion polymerizations in methanol/water media. The first seeded dispersion polymerization was carried out with 2-μm-sized, monodispersed PMMA particles.     

Production of micron-sized monodispersed core/shell polymethyl methacrylate/polystyrene particles by seeded dispersion polymerization

 Micron-sized monodispersed polymethyl methacrylate (PMMA)/polystyrene (PS) (PMMA/PS=2/1, wt ratio) composite particles consisting of PMMA-core and PS-shell were successfully produced by seeded dispersion polymerization of styrene in a methanol/water medium in the presence of about 2 μm-sized monodispersed PMMA particles. From the view point of thermodynamic equilibrium, such a morphology is difficult to form by usual seeded polymerization in a polar medium such as water. It is concluded that seeded dispersion polymerization in which almost all monomers and initiators exist in the medium has an advantage to produce core/shell polymer particles in which polymer layers accumulate in their order of the production regardless of the hydrophobicity of polymers, because of high viscosity in polymerizing particles. Received: 9 December 1996 Accepted: 26 February 1997     

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     

Morphology of micron-sized monodispersed composite polymer particles produced by seeded polymerization for the dispersion of highly monomer-swollen polymer particles

 Monodispersed polystyrene (PS)/poly(n-butyl methacrylate) (PBMA) composite particles having 9.4 μm in diameter were produced by seeded polymerization for the dispersion of highly n-butyl methacrylate (BMA)-swollen PS particles, and their morphologies were examined. The highly BMA-swollen PS particles (about 150 times the weight of the PS seed particles) were prepared by mixing monodispersed 1.8 μm-sized PS seed particles and 0.7 μm sized BMA droplets prepared with an ultrasonic homogenizer in ethanol/water (1/2, w/w) medium at room temperature. After NaNO₂ aqueous solution as inhibitor was added in the dispersion, the seeded polymerization was carried out at 70 °C. In an optical microscopic observation, one or two spherical high contrast regions which consisted mainly of PS were observed inside PS/PBMA composite particles. In the PS domain, there were many fine spherical PBMA domains. Such morphologies were based on the phase separation of PS and PBMA within the homogeneous swollen particles during the seeded polymerization. Received: 04 June 1997 Accepted: 27 August 1997     

Synthesis and characterization of dual‐responsive micrometer‐sized core‐shell composite polymer particles

Dual‐responsive micrometer‐sized core‐shell composite polymer particles were prepared by dispersion polymerization followed by seeded copolymerization. Polystyrene (PS) particles prepared by dispersion polymerization were used as core particles. N‐isopropyl acrylamide (NIPAM) and methacrylic acid (MAA) were used to induce dual‐responsive that is thermo‐ and pH‐responsive properties in the shell layer of composite polymer particles, prepared by seeded copolymerization with PS core particles. Temperature‐ and pH‐dependent adsorption behaviors of some macromolecules on composite polymer particles indicate that produced composite polymer particles exhibit dual‐responsive surface properties. Copyright © 2007 John Wiley & Sons, Ltd.     

Thermoresponsive poly(ionic liquid): Controllable RAFT synthesis,thermoresponse, and application in dispersion RAFT polymerization

The thermoresponsive poly(ionic liquid) of poly[1‐(4‐vinylbenzyl)‐3‐methylimidozolium tetrafluoroborate] trithiocarbonate (P[VBMI][BF₄]‐TTC) showing the soluble‐to‐insoluble phase transition in the methanol/water mixture at the upper critical solution temperature (UCST) was synthesized by solution RAFT polymerization and the synthesized P[VBMI][BF₄]‐TTC was employed as macro‐RAFT agent to mediate the RAFT polymerization under dispersion condition to afford the thermoresponsive diblock copolymer nanoparticles of poly[1‐(4‐vinylbenzyl)‐3‐methylimidozolium tetrafluoroborate]‐b‐polystyrene (P[VBMI][BF₄]‐b‐PS). The controllable solution RAFT polymerization was achieved as indicated by the linearly increasing polymer molecular weight with the monomer conversion and the narrow molecular weight distribution. The P[VBMI][BF₄]‐TTC macro‐RAFT agent mediated dispersion polymerization afforded the P[VBMI][BF₄]‐b‐PS nanoparticles, the size of which was uncorrelated with the polymerization degree of the P[VBMI][BF₄] block. Several parameters including the polymerization degree, the polymer concentration and the water content in the solvent of the methanol/water mixture were found to be correlated with the UCST of the poly(ionic liquid). The synthesized poly(ionic liquid) is believed to be a new thermos‐responsive polymer and will be useful in material science. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 945–954     

Production of micron-sized monodispersed core/shell composite polymer particles by seeded dispersion polymerization

 The effect of the weight ratio of seed polymer/monomer on the morphology of the poly(methyl methacrylate) (PMMA)/polystyrene (PS) monodispersed composite particles produced by batch seeded dispersion polymerization of styrene with 1.64-μm-sized monodispersed PMMA seed particles in a methanol/water medium (4/1 w/w) was examined. In the PMMA/PS weight ratios of 3/1 and 2/1, the composite particles had a clear morphology consisting of a PMMA core and a PS shell. In the ratio of 1/1, a lot of small PS domains were observed in the PMMA core though the PS shell was still formed. By stepwise addition of styrene monomer, the formation of the small PS domain was depressed and complete core/shell morphology was formed. Absorption/release treatments of toluene into/from the PMMA/PS (1/1 w/w) composite particles resulted in a drastic morphological change from the core/shell structure to a multi- layered one. Received: 2 February 1999 Accepted in revised form: 7 April     

Effect of graft polymer on the formation of micron-sized,monodisperse, "onion-like" alternately multilayered poly(methyl methacrylate)/polystyrene composite particles by reconstruction of morphology with the solvent-absorbing/releasing method

Some factors contributing to the formation of an alternately multilayered structure of micron-sized, monodisperse poly(methyl methacrylate) (PMMA)/polystyrene (PS) (1/1, w/w) composite particles by reconstruction of the morphology with the solvent-absorbing/releasing method (SARM) were discussed. The original composite particles, which were produced by seeded dispersion polymerization (SDP) of styrene, had a core–shell structure. When PS/PMMA (1/1, w/w) composite particles produced by SDP of methyl methacrylate were treated by the SARM with toluene, the reconstructed morphology of the composite particles was not the multilayered structure but a hemisphere (or core–shell). The PS/PMMA composite particle contained less than 10 wt% PMMA- g-PS. On the other hand, the PMMA/PS composite particles contained about 40 wt% graft polymer. The graft polymer would exist at the interfaces of the alternate multilayers and decrease their interfacial energy. This was the main reason why the alternately multilayered structure was constructed by the SARM, though the total interfacial area between PMMA and PS layers in the multilayered particle is much larger than that of the hemisphere (or core–shell).     

Polymerization‐induced self‐assembly of block copolymer through dispersion RAFT polymerization in ionic liquid

Polymerization‐induced self‐assembly of block copolymer through dispersion RAFT polymerization has been demonstrated to be a valid method to prepare block copolymer nano‐objects. However, volatile solvents are generally involved in this preparation. Herein, the in situ synthesis of block copolymer nano‐objects of poly(ethylene glycol)‐block‐polystyrene (PEG‐b‐PS) in the ionic liquid of 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([BMIN][PF₆]) through the macro‐RAFT agent mediated dispersion polymerization is investigated. It is found that the dispersion RAFT polymerization of styrene in the ionic liquid of [BMIN][PF₆] runs faster than that in the alcoholic solvent, and the dispersion RAFT polymerization in the ionic liquid affords good control over the molecular weight and the molecular weight distribution of the PEG‐b‐PS diblock copolymer. The morphology of the in situ synthesized PEG‐b‐PS diblock copolymer nano‐objects, e.g., nanospheres and vesicles, in the ionic liquid is dependent on the polymerization degree of the solvophobic block and the concentration of the fed monomer, which is somewhat similar to those in alcoholic solvent. It is anticipated that the dispersion RAFT polymerization in ionic liquid broads a new way to prepare block copolymer nano‐objects. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1517–1525     

Production of micron-sized monodispersed composite polymer particles by seeded polymerization utilizing the dynamic swelling method

 In order to develop the seeded polymerization technique utilizing the dynamic swelling method (DSM) proposed by authors for the production of micron-sized mono-dispersed “composite” polymer particles consisting of two kinds of polymers, the seeded polymerization for the dispersion of ethyl methacry-late (EMA)-swollen PS particles prepared utilizing DSM was carried out. Monodispersed PS/poly(ethyl methacrylate) (PEMA) composite particles having 7 μm in diameter were produced by the addition of NaCl to lower the solubility of EMA in medium and by the addition of CuCl₂ as a water-soluble inhibitor to depress the by-production of submicron-sized PEMA particles. Received: 16 July 1996 Accepted: 10 October 1996     

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     

聚苯乙烯/Ag核壳结构纳米微粒的制备及表征

用种子乳液聚合法合成了聚苯乙烯（PS）/Ag复合纳米粒子,进一步利用分步聚合技术实现了聚甲基丙烯酸甲酯(PMMA)在微球表面功能化,分别用TEM、XRD、TG-DTA及FT-IR对其结构和形貌进行了表征,并考察了其摩擦学性能.结果表明,在所选择的实验条件下,合成了以Ag纳米微粒为核,PS、PMMA为壳层的核壳结构复合纳米微球,其中Ag纳米核平均粒径约12 nm,复合微球粒径约25 nm,颗粒较均匀并且在有机溶剂中有良好的分散性,作为润滑油添加剂,具有良好的抗磨性能.     

Preparation of Nylon-6 Particles in Ionic Liquids

Summary: Utilizing the thermal stability of ionic liquid, micrometer-sized Nylon-6 particles were successfully prepared by hydrolytic polymerization of ε-caprolactam at high temperature with polyvinyl pyrrolidone as stabilizer in ionic liquids, 1-butyl-3-methyl imidazolium tetrafluoroborate, [Bmim][BF₄] and N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoro-methanesulfonyl)amide, [DEME][TFSA]. The obtained particles had a unique shape because Nylon-6 is a crystalline polymer. Viscosity-average molecular weights of Nylon-6 prepared in [Bmim][BF₄] and [DEME][TFSA] at 180 °C for 48 h were 4200 and 2200, respectively.     

Preparation of micron-sized composite polymer particles containing hydrophilic 2-hydroxyethyl methacrylate and their biomedical applications

Micron-sized polystyrene or PS particles were first prepared by dispersion polymerization. Then a series of polystyrene/poly(styrene-2-hydroxyethyl methacrylate) or PS/P(S-HEMA) composite polymer particles was prepared by seeded copolymerization using different amounts of 2-hydroxyethyl methacrylate (HEMA) at the constant core/shell ratio of 1/0.5. The produced PS seed and composite polymer particles were characterized by transmission electron microscopy. Adsorption behaviors of some biologically active macromolecules were studied under similar conditions. In each case the magnitude of adsorption on composite polymer particles decreased with the increase in HEMA content in the recipe, which means that the hydrophobic interaction between the surface of the particles and biomolecules decreased. The specific activities of trypsin aqueous solution and adsorbed trypsin on PS seed and composite polymer particles prepared with different HEMA contents were also measured and compared. The activity of adsorbed trypsin on composite polymer particles improved significantly with the incorporation of hydrophilic HEMA.     

Influence of viscosity within polymerizing particle on the morphology of micron-sized,monodisperse composite polymer particles produced by seeded polymerization for the dispersion of highly monomer-swollen polymer particles

Micron-sized, monodisperse polystyrene (PS)/poly( n-butyl methacrylate) (PBMA) composite particles, in which PS domain(s) were dispersed in a PBMA continuous phase, were produced by seeded polymerization for the dispersion of highly n-butyl methacrylate (BMA)-swollen PS particles (PS/BMA=1/150, w/w) using various concentrations of benzoyl peroxide as initiator in the absence/presence of sodium nitrite (NaNO ₂) as a water-soluble inhibitor. The percentages of the composite particles having double, triple and over PS domains, which were thermodynamically unstable morphologies, increased with a rapid increase of viscosity within the polymerizing particle.     

Preparation of Polystyrene Particles by Dispersion Polymerization in an Ionic Liquid

Submicron‐sized monodisperse polystyrene (PS) particles were successfully prepared by dispersion polymerization of styrene in an ionic liquid, N,N‐diethyl‐N‐methyl‐N‐(2‐methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide ([DEME][TFSI]) at 70 °C with poly(vinyl pyrrolidone) (PVP) as a stabilizer. At the optimum PVP and styrene concentrations with regard to preparation of stable polymer particles, the number‐average diameter and coefficient of variation were 350 nm and 5.7%, respectively. The particle size increased with a decrease in the PVP concentration and an increase in the styrene concentration. Moreover, we succeeded in producing PS particles by thermal polymerization in the absence of a radical initiator at 130 °C in [DEME][TFSI] using a conventional reactor (not autoclave) utilizing the advantages of non‐volatility and thermal stability of the ionic liquid.

     

Monodisperse polystyrene particles crosslinked with poly(dimethyl siloxane) diacrylate using dispersion polymerization and their monomer swelling capability

A flexible poly(dimethyl siloxane) diacrylate (PDMSDA) crosslinker was synthesized using different molecular weights of poly(dimethyl siloxane) (PDMS, M _n =550, 1,700, 4,000 g/mol). The monodisperse polystyrene (PS) particles crosslinked with various contents of PDMSDA were prepared by dispersion polymerization, and applied as seed particles in the seeded polymerization. The crosslinking density of the PS particles was determined from the rate of transport of the monomer molecules to the crosslinked seed particles. It was confirmed that the monomer swelling capacity of seed particles and final morphological changes of polymer beads were determined significantly by the crosslinking density of the seed particles. In addition, the morphological change was not observed without the oligomer swelling step in the seeded polymerization due to the hydrophobic property of PDMS. When highly crosslinked seed particles were used in the seeded polymerization, peculiar morphology (doublet structure) of polymer beads appeared.     

Preparation of Hemispherical Polymer Particles by Cleavage of a Janus Poly(methyl Methacrylate) /Polystyrene Composite Particle

Micrometer-sized, hemispherical particles were successfully prepared as a result of the cleavage of Janus PMMA/PS composite particles by dispersion into acetone/water (9/1-10/0 v/v) media or a THF/water (8/2 v/v) medium. The spherical composite particles having a Janus structure were prepared by the slow evaporation of toluene from homogeneous PMMA/PS/toluene droplets dispersed in an aqueous medium in advance. It was clarified that the difference in affinity between PMMA and PS phases with respect to the media caused the cleavage of the composite particles. This method is expected to be a novel approach to the preparation of nonspherical polymer particles.     

Preparation and thermodynamic stability of micron-sized, monodisperse composite polymer particles of disc-like shapes by seeded dispersion polymerization

Micron-sized, monodisperse composite polymer particles having "disc-like" and "polyhedral" shapes were prepared by seeded dispersion polymerization of 2-ethylhexylmethacrylate (EHMA) with 2.67-mum-sized polystyrene (PS) seed particles in methanol/water media in the presence of droplets of various saturated hydrocarbons and evaporation of the hydrocarbon after the polymerization. Such nonspherical shapes were based on the volume reduction due to the evaporation. The primary factors influencing the particle shape seemed to be the absorption rate of the hydrocarbon into the resulting PS/poly(EHMA)/hydrocarbon composite particles during the polymerization, which affected the viscosities and the volumes of the PS and poly(EHMA) phases. It was found that the morphological development during the polymerization was retarded at "hamburger-like" morphology, which is a precursor of the disc-like particle, although this morphology is a thermodynamically metastable state.     

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 .