Monodisperse,controlled micron-size dye-labeled polystyrene particles by two-stage dispersion polymerization

Monodisperse controlled micron-sized colored polystyrene particles have been prepared by two-stage dispersion copolymerization with polymerizable dyes. These polymerizable dyes have a methacrylate moiety for copolymerization with styrene and suitable spacers between the dye nucleus and the methacrylate function to promote the solubility of the dye. In the past, various research groups have found that when they added a dye-comonomer to a traditional dispersion polymerization recipe, they obtained poor results. The final particle size changed significantly; and the size distribution became broader. In the two-stage method, we defer the addition of the dye-comonomer until the nucleation stage is complete. These dyes become incorporated into the particles without disturbing the final particle size and size distribution.     

Thixotropic interparticle interaction between silica and nonionic polymer particles prepared by static dispersion polymerization

Static dispersion polymerization of styrene, methyl methacrylate, ethyl methacrylate, butyl methacrylate and benzyl methacrylate, initiated by a lipophilic initiator in an aqueous dispersion with unmodified silica particles was investigated. Polymerization of styrene gave a mixed dispersion of silica and monodisperse polystyrene (PS) particles, which was extremely stable compared with the aqueous dispersion of silica particles. The enhanced dispersion stability is due to a thixotropic effect based on weak attractive interparticle interactions between silica and PS particles in aqueous dispersion. An aggregate in which silica particles are surrounded by the smaller PS particles is formed and inhibits flocculation of silica particles, thus giving enhanced dispersion stability. The results of similar static polymerization reactions with methacrylate analogs indicate that hydrogen bonds between benzene ring and hydroxy groups on the silica surface, and not electrostatic interaction derived from initiator residues, are the origin of weak interaction for thixotropic aggregation.     

Monodisperse carboxylated polystyrene particles: synthesis, electrokinetic and adsorptive properties

Effect of conditions of styrene dispersion polymerization initiated by 4,4′-azo-bis-(4-cyanopentanoic acid) in ethanol solutions of polyvinylpyrrolidone was investigated. Suitable methods ensuring the control of final particle size, surface structure, and surface concentration of carboxylic groups in the polymerization process are discussed. Particle ability to interact with protein was also studied. Monodisperse particles of diameters up to 4 μm had a complex surface layer containing polyvinylpyrrolidone-graft-polystyrene copolymers as well as carboxylic groups of the initiator. The effect of this surface structure on the isotherms of adsorption and chemisorption of bovine serum albumin was revealed. Electrophoretic mobility of the particles and their isoelectric point values before and after protein binding depending on pH and ionic strength were determined. These data depend on conditions of particle preparation as well as on protein coating values.     

Preparation of raspberry‐like poly(methyl methacrylate) particles by seeded dispersion polymerization

The facile preparation of nonspherical raspberry‐like poly(methyl methacrylate) (PMMA) particles by seeded dispersion polymerization of methyl methacrylate (MMA) on micron‐sized PMMA seed particles was described. Various polymerization parameters influencing the particle morphology, as well as the polymerization kinetic and morphological stability, were investigated in detail. It was found that the following polymerization conditions were necessary to prepare this kind of nonspherical particles: a relatively low temperature, an appropriate ratio of seed/MMA, an initiator with a relatively low decomposition rate, and a relatively low initiator concentration. These particles showed very good morphological stability at room temperature, but they changed to the spherical ones when heat treated at 60°C in methanol solution of MMA. The experimental results suggest that the prepared PMMA particles were kinetically favored and the localized polymerization of the MMA monomer on PMMA seed particle surface was responsible for the formation of the raspberry‐like particles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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     

辐射引发分散聚合反应制备聚合物微球研究进展

介绍了辐射作用原理、辐射引发分散聚合反应技术和机理、及其最新研究进展：重点阐述了超声、紫外光、γ射线、微波辐射在分散聚合中的应用。     

Formation of monodisperse polyacrylamide particles by radiation‐induced dispersion polymerization. I. Synthesis and polymerization kinetics

Highly monodisperse polyacrylamide (PAM) microparticles were directly prepared by radiation‐induced dispersion polymerization at room temperature in an aqueous alcohol media using poly(N‐vinylpyrrolidone) (PVP) as a steric stabilizer. Monomer conversion was studied dilatometrically and polymer molecular weight was determined viscometrically. The gel effect was found evidently from the polymerization kinetics curves. The influence of the dose rate, monomer concentration, stabilizer content, medium polarity, polymerization temperature on the polymerization rate, and the molecular weight of the polymer was examined. The polymerization rate (Rp) can be represented by Rp ∝ D^0.15[M]^0.86[S]^0.47[A/W]^0.64 and the molecular weight of the polymer can be represented by M_w ∝ D^?0.19 [M]^1.71[S]^0.43[A/W]^0.14 at a definite experimental variation range. The overall activation energy for the rate of polymerization is 10.57 kJ/mol (20–35°C). Based on these experimental results, the polymerization mechanisms were discussed primarily. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2567–2573, 2002     

Formation of monodisperse polyacrylamide particles by dispersion polymerization: particle size and size distribution

Highly monodisperse polyacrylamide microparticles were directly prepared by dispersion polymerization in aqueous alcoholic media initiated by 2,2′‐azobisisobutyronitrile using poly(N‐vinylpyrrolidone) as a steric stabilizer. Monomer conversion was studied dilatometrically and polymer molecular weight was determined viscometrically. The hydrodynamic diameter of polymer particles and its distribution were measured with a dynamic laser light scattering spectrometer. The number of the nuclei produced in the early stage of the polymerization was found to be constant during the remainder of the polymerization. The influences of various polymerization parameters, such as initiator concentration, monomer concentration, stabilizer content, medium polarity, and polymerization temperature on the particle size and size distribution were systematically investigated. Copyright © 2003 Society of Chemical Industry     

Synthesis of latex particles by ring-opening metathesis polymerization

This paper reviews the recent discoveries that were achieved by our group in the field of particle synthesis via ring-opening metathesis polymerization (ROMP). Both polynorbornene and polybutadiene-based particles were prepared by the respective ROMP of norbornene and cyclooctadiene initiated by (PCy₃)₂Cl₂RuCHPh using several methods of polymerization in dispersed media, such as dispersion, suspension and miniemulsion. Depending upon the process implemented, particles size was found to range from 300 nm to 20 μm.     

Monodisperse micron-sized polystyrene particles by seeded polymerization using reactive macrosurfactants

Monodisperse micron-sized polystyrene particles could be prepared through a two-staged seeded swelling and polymerization method using reactive surfactants. The seed was obtained by emulsifier-free emulsion polymerization. To prepare conventional surfactant-free monomer emulsion droplet in swelling process, a tri-block diol diacrylate (t-BDDA), which is poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) tri-block copolymer containing two chain ends capped with acryloyl chloride, was employed as a reactive surfactant instead of conventional surfactants. Thermodynamic consideration of the effect of monomer droplet size and interfacial tension on the swelling process ensured that two-staged monomer swelling could be effectively performed by using t-BDDA as a surface-active macromonomer. From the surface tension measurement and optical microscope observation, it was found that the t-BDDA had a favorable surface activity when the monomer emulsion was prepared under its cloud point. From the X-ray photoelectron spectroscopy, it was found that most of the t-BDDA resided on the final particle surfaces.     

Synthesis of spike‐ball‐like polystyrene/poly(methyl methacrylate) composite particles via seeded polymerization

A synthesis method for the production of novel spike‐ball‐like polymer particles is presented based on seeded dispersion polymerization of methyl methacrylate monomer in the presence of polystyrene seeds with poly(vinyl alcohol) as stabilizer and myristyl peroxydicarbonate as initiator. The particles resulting from the controlled aggregation of swollen particles during polymerization showed a salami‐like morphology with polystyrene cores and poly(methyl methacrylate) shells. The long spikes had the same morphology and were formed by the step‐by‐step addition of smaller particles on the surface of the larger particles during polymerization. The resulting particles have potential applications as templates to make micron‐sized electronics and biomaterials. © 2017 Society of Chemical Industry     

Homogeneously distributed magnetite in the polystyrene spherical particles using the miniemulsion polymerization

The polystyrene spherical particles with homogeneously distributed magnetites were prepared using the conventional miniemulsion polymerization. In the first, the magnetite nanoparticles were coated with oleic acid in aqueous Fe³⁺/Fe²⁺ solution using excess ammonium hydroxide via co-precipitation method. In the second, the miniemulsion polymerization of styrene was carried out using various concentrations of potassium persulfate (KPS) as an initiator, H-08E as an emulsifier, hexadecane as a co-emulsifier and acrylic acid as a dispersing agent in the presence of oleic acid coated magnetite at 70 °C for 24 h. The particle size and its distribution of the homogeneously embedded magnetites were influenced by the concentration of the initiator (KPS) and acrylic acid (AAc). In addition, the emulsifier, H-08E, affects the size and the shape of the PS particles. The optimum conditions for the homogeneously distributed magnetite in the spherical PS particles with the narrow distribution were 5 wt.% styrene, 0.2 g KPS, 0.2 g AAc, and 0.12 g H-08E by inducing 364 nm in diameter, 12.04% in the coefficient of variation (C_v) and 22.1% of the maximum magnetite content.     

Monodisperse magnetic composite poly(glycidyl methacrylate)/La0.75Sr0.25MnO3 microspheres by the dispersion polymerization

Monodisperse magnetic poly(glycidyl methacrylate) microspheres were prepared by dispersion polymerization of glycidyl methacrylate in cyclohexane in the presence of La_0.75Sr_0.25MnO₃ nanoparticles, surface of which was modified with penta(propylene glycol) methacrylate phosphate (PPGMAP). However, only agglomerates were formed by the dispersion polymerization in toluene. Sterical stabilizer was poly(styrene-block-hydrogenated butadiene-block-styrene) and initiators investigated were 2,2′-azobisisobutyronitrile (AIBN) and 4,4′-azobis(4-cyanovaleric acid) (ACVA). Effects of initiators and other reaction conditions on properties of the composite microspheres were evaluated. The phase composition of the magnetic polymer composite microspheres and the size of magnetic cores were determined by X-ray powder diffraction. The characterization was completed by magnetization measurements, atomic absorption spectroscopy, TEM, SEM and ATR FTIR spectroscopy.     

分散聚合法制备亚微米级单分散聚苯乙烯微球

以醇和水的混合液为分散介质,聚乙烯基吡咯烷酮（PVP）为分散剂、偶氮二异丁腈（AIBN）为引发剂,利用分散聚合法制备亚微米级的单分散聚苯乙烯（PS）微球。分别讨论分散剂的用量以及分散介质的溶解度参数对PS微球粒径的影响。结果表明,当分散介质溶解度参数和单体苯乙烯的溶解度参数越接近时,所制得的PS微球粒径越大,反之越小;随着分散剂PVP量的增加,微球的粒径减小,粒径分布变窄;所制得的聚苯乙烯微球表面光滑,呈均匀的球形。     

Preparation and characterization of titanium dioxide core and polymer shell hybrid composite particles prepared by two-step dispersion polymerization

Titanium dioxide core and polymer shell composite poly (styrene-co-divinylbenzene)-methacrylic acid [P (St-co-DVB)-MAA]] particles were prepared by two-step dispersion polymerization. Fourier transform IR spectroscopy and elemental analysis were used to measure the content of methacrylic acid in composites particles. X-ray measurement photoelectron spectroscopy (XPS) measurements indicated the presence of an MAA unit on the surface of the composite particles. The combined results of the elemental analysis and the XPS measurements showed that the copolymer on the surface of poly (St-co-DVB)-MAA composite particles was rich in MAA compared with that in the interior of the composite particles. Field-emission scanning electron microscopy (FE-SEM) was used to study the morphology characterization. The composite particles produced showing good spectral reflectance compare with bare TiO₂. TGA results indicated that the encapsulation efficiency and estimated density of composite particles. Encapsulation of TiO₂ was up to 87.4% and the density was ranged from 1.78 to 2.06 g/cm³. Estimated density of the composite particles is suitable to 1.73 g/cm³, due to density matching with suspending fluid.     

Preparation and characterization of porous poly(methacrylic acid) gel by dispersion polymerization

Porous poly(methacrylic-co-glycidylmethacrylate) (MAA-GM) was prepared by dispersion polymerization using benzoyl peroxide as an initiator and methacrylate terminated phthalate glycol polyester as a steric stabilizer in polar organic medium (chloroform–ethanol mixture). The prepared poly(methacrylic acid) dispersion was crosslinked by glycidylmethacrylate oligomers. The crosslinked copolymer (MAA-GM) was base hydrolyzed using hydroxyl amine, sodium methoxide, and triethyl amine. The metal binding behavior of the prepared polymer was examined by means of atomic absorption spectrophotometer. The thermal stability of the prepared polymers was examined by thermal gravimetric analysis (TGA). © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1793–1798, 1999     

Preparation of monodisperse poly(methyl methacrylate) particles by radiation-induced dispersion polymerization using vinyl terminus polysiloxane macromonomer as a polymerizable stabilizer

Monodisperse poly(methyl methacrylate) particles were prepared directly by radiation-induced dispersion polymerization in hexane-ethanol media using vinyl terminus polysiloxane (PSI) macromonmer as a polymerizable stabilizer at room temperature. This method takes advantage of the specialties of radiation-induction, which may result in the formation of uniform polymer particles. The gel effect is evident from the polymerization kinetics curves. Vinyl terminus PSI macromonomer acted as not only a comonomer, but also as a stabilizer. The characterization of PMMA particles was carried out by the scanning electron microscope (SEM), FT-IR, ¹H-NMR and X-ray photoelectron spectroscope (XPS). XPS results show that the graft PSI macromonomers were anchored on the surface of PMMA particles to provide a steric stabilization to the PMMA particles.     

Monodisperse ellipsoidal polystyrene latex particles: Preparation and characterisation

An improved version of a novel method first employed by Nagy & Keller for the preparation of monodisperse ellipsoidal polystyrene latex particles is described. The method involves embedding monodisperse spherical polystyrene latex particles as starting material in a deformable polymer matrix such as poly(vinyl alcohol) and deforming these mechanically to various predetermined macroscopic draw ratios to give ellipsoids of various axial ratios. Ellipsoids with lengths ranging from about 350 to 12250nm were prepared. Stable aqueous dispersions of these were recovered and characterised with respect to particle size and axial ratio distributions and surface morphology using electron microscopy. Axial ratios ranging from 2.0 to 5.65 were obtained for the resulting ellipsoids. Various factors influencing the monodispersity of the resulting ellipsoids in the preparation method are discussed.     

Tracking the fate of seed particles in dispersion polymerization: Preparation and application of fluorescent polymer particles

The mechanism of seeded dispersion polymerization of methyl methacrylate (MMA) was investigated by employing submicron fluorescent polymer particles as seed. These poly(methyl methacrylate) latex particles, containing fluorescent material, were synthesized by a two‐step miniemulsion polymerization process and then applied in the seeded dispersion polymerization of MMA. The seed particles were located by tracking the fluorescent signal in the micron‐size final particles. The analysis of the final particles showed that most of them contained more than two seed particles. On average, there were 3.7 seed particles in each final particle as obtained under the given conditions of the seeded dispersion polymerization. The location of the seed within the particles being well‐separated from each other was considered to indicate that the aggregation of the particles did not occur immediately, but took place after some particle growth had first taken place. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation of monodisperse polystyrene spheres incorporating polyimide prepolymer by dispersion polymerization in the presence of L-ascorbic acid

Addition of a small amount of L -ascorbic acid (AA) unexpectedly provided uniform-sized polystyrene (PS) spheres in an ordinary dispersion polymerization process. PS spheres incorporated with polyimide prepolymer (BANI-M), designed as possible spacers for liquid crystal displays, were prepared from formulations containing a mixed solvent of isopropanol/2-methoxyethanol, 2,2′-azobisisobutyronitrile, and poly-N-vinylpyrrolidone (PVP) at 343 K. The average particle size decreased by the addition of AA; however, dramatic improvements of monodispersity were observed with various formulations. The best coefficient of variation was 1.37%, compared to 7.03% obtained without the presence of AA. Addition of AA was originally intended to scavenge a trace amount of oxygen remaining in the reactor system, promoting a rapid and short particle nucleation period, and thereby resulting in improved monodispersity. However, there was no difference in the initial reaction rate between the runs with and without AA; no noticeable induction period was observed even without AA provided that an ordinary procedure was employed to eliminate the dissolved oxygen through a nitrogen bubbling, and the nitrogen atmosphere was maintained during the reaction. It was proposed from ¹H-NMR analysis that the abstraction of hydrogen atom from the PVP chain by the oxidized form of AA promoted the formation of graft copolymer PVP-PS, which stabilizes precipitating chains in the nucleation period. Approximately 40% of BANI-M present initially was incorporated in the PS particles, which occupied 4–9% of the weight of polymer particles, well below the target value of 20%. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 897–907, 1998