Synthesis and characterization of magnetic and non-magnetic core-shell polyepoxide micrometer-sized particles of narrow size distribution

Core polystyrene microspheres of narrow size distribution were prepared by dispersion polymerization of styrene in a mixture of ethanol and 2-methoxy ethanol. Uniform polyglycidyl methacrylate/polystyrene core-shell micrometer-sized particles were prepared by emulsion polymerization at 73 degrees C of glycidyl methacrylate in the presence of the core polystyrene microspheres. Core-shell particles with different properties (size, surface morphology and composition) have been prepared by changing various parameters belonging to the above seeded emulsion polymerization process, e.g., volumes of the monomer glycidyl methacrylate and the crosslinker monomer ethylene glycol dimethacrylate. Magnetic Fe(3)O(4)/polyglycidyl methacrylate/polystyrene micrometer-sized particles were prepared by coating the former core-shell particles with magnetite nanoparticles via a nucleation and growth mechanism. Characterization of the various particles has been accomplished by routine methods such as light microscopy, SEM, FTIR, BET and magnetic measurements.     

Surface modification of crosslinked poly(styrene-divinyl benzene) micrometer-sized particles of narrow size distribution by ozonolysis

Micrometer-sized polystyrene template particles of narrow size distribution were prepared by dispersion polymerization of styrene in 2-methoxyethanol. Uniform micrometer-sized polystyrene/crosslinked poly(styrene-divinyl benzene) composite particles were formed by a single-step swelling process of the template particles with styrene, divinyl benzene and benzoyl peroxide, followed by polymerization at 70 degrees C. Uniform micrometer-sized crosslinked poly(styrene-divinyl benzene) particles of higher surface area were produced by dissolution of the template polystyrene part of the former composite particles with N,N-dimethylformamide. Hydroperoxide conjugated crosslinked poly(styrene-divinyl benzene) particles were produced by ozonolysis of these particles. The effect of ozonolysis conditions, such as exposure time and flow rate of the ozone, on the hydroperoxide conjugation to the crosslinked particles was also studied. Functionalization of the crosslinked poly(styrene-divinyl benzene) particles was performed by graft polymerization of vinylic monomers such as acrylonitrile and chloromethylstyrene on the hydroperoxide conjugated crosslinked particles. This was accomplished by raising the temperature (e.g., 70 degrees C) of deairated acetonitrile dispersions containing the hydroperoxide conjugated particles and the vinylic monomers. The influence of various polymerization parameters on the grafting yield, e.g., monomer concentration, conjugated hydroperoxide concentration, and temperature, was also elucidated.     

Synthesis and characterization of magnetic poly(divinyl benzene)/Fe3O4, C/Fe3O4/Fe, and C/Fe onionlike fullerene micrometer-sized particles with a narrow size distribution

Magnetic poly(divinyl benzene)/Fe(3)O(4) microspheres with a narrow size distribution were produced by entrapping the iron pentacarbonyl precursor within the pores of uniform porous poly(divinyl benzene) microspheres prepared in our laboratory, followed by the decomposition in a sealed cell of the entrapped Fe(CO)(5) particles at 300 °C under an inert atmosphere. Magnetic onionlike fullerene microspheres with a narrow size distribution were produced by annealing the obtained PDVB/Fe(3)O(4) particles at 500, 600, 800, and 1100 °C, respectively, under an inert atmosphere. The formation of carbon graphitic layers at low temperatures such as 500 °C is unique and probably obtained because of the presence of the magnetic iron nanoparticles. The annealing temperature allowed control of the composition, size, size distribution, crystallinity, porosity, and magnetic properties of the produced magnetic microspheres.     

Preparation and characterization of well-defined sterically stabilized latex particles with narrow size distribution

 The synthesis and comprehensive characterization of a purely sterically stabilized latex with narrow size distribution is reported. By use of non-ionic initiators no chemically bound surface charges are generated. Stabilization of the particles is achieved through use of a non-ionic surfactant having a double bond in the hydrophobic part which is chemically bound to the surface. Analysis of the latex particles thus generated by transmission electron microscopy, disc centrifugation, and small-angle X-ray scattering (SAXS) reveals that the size distribution is narrow (standard deviation between 6 and 10%). SAXS furthermore demonstrates that the surfactant is located in a thin layer on the surface. The interaction of the particles is purely repulsive as shown by the analysis of the turbidity of the latex. The systems obtained herein may serve as model systems of water-borne purely sterically stabilized colloid particles. Received: 23 December 1997 Accepted: 18 May 1998     

Synthesis and characterization of fluorescently labelled poly(vinyl acetate) particles

Nonaqueous dispersions of poly(vinyl acetate) particles stabilized with poly(2-ethylhexyl methacrylate) and labelled with fluorescent dyes in the core and stabilizer polymer phases were prepared. The materials were characterized using a broad range of techniques (NMR, UV, and fluorescence spectroscopy. GPC, particle sizing, and DSC). The data show that dispersion polymerization of vinyl acetate in the presence of stabilizers containing certain fluorescent dye derivatives, instead of unlabelled stabilizer, results in changes in the mean particle size, size distribution, composition, and molecular weights of the colloidal polymer particles. It was found that increasing the amounts of fluorescent groups in the stabilizer resulted in smaller mean particle sizes and larger amounts of irreversibly attached stabilizer. When the average number of labels in stabilizer exceeded one per chain, a new ultra-high molecular weight polymer fraction appeared. The fluorescence spectra for several of these materials are reported. We describe how fluorescence decay curves can be used to assess block formation and local phase separation in particles labelled with phenanthrene groups. These materials are intended to be used for more detailed studies by fluorescence spectroscopy. Those results will be published in due course.     

Synthesis and characterization of poly(3-sulfopropylmethacrylate) brushes for potential antibacterial applications

This article describes the aqueous atom transfer radical polymerization synthesis of poly(3-sulfopropylmethacrylate) brushes onto gold and Si/SiO2 surfaces in a controlled manner. The effect of Cu(I)/Cu(II) ratio was examined, and a quartz crystal microbalance was used to study the kinetics of the brush synthesis. The synthesized brushes displayed a thickness from a few nanometers to several hundred nanometers and were characterized using atomic force microscopy, ellipsometry, Fourier transform infrared spectroscopy (FTIR), contact angle measurements, and X-ray photoelectron spectroscopy (XPS). The as-synthesized sulfonate brushes had very good ion-exchange properties for the ions tested in this study, i.e., Na+, K+, Cu2+, and Ag+. FTIR and XPS show that the metal ions are coordinating to sulfonate moieties inside the brushes. The brushes were easily loaded with silver ions, and the effect of silver ion concentration on silver loading of the brush was examined. The silver-loaded brushes were shown to be antibacterial toward both gram negative and gram positive bacteria. The silver leaching was studied through leaching experiments into water, NaNO3, and NaCl (physiological medium). The results from these leaching experiments are compared and discussed in the article.     

Online aerosol mass spectrometry of single micrometer-sized particles containing poly(ethylene glycol)

The analysis of poly(ethylene glycol) (PEG)-containing particles by online single particle aerosol mass spectrometers equipped with laser desorption/ionization (LDI) is reported. We demonstrate that PEG-containing particles are useful in the development of aerosol mass spectrometers because of their ease of preparation, low cost, and inherently recognizable mass spectra. Solutions containing millimolar quantities of PEGs were nebulized and, after drying, the resultant micrometer-sized PEG-containing particles were sampled. LDI (266 nm) of particles containing NaCl and PEG molecules of average molecular weight<500 Da generated mass spectra reminiscent of mass spectra of PEG collected by other mass spectrometer platforms including the characteristic distribution of positive ions (Na+ adducts) separated by the 44 m/z units of the ethylene oxide units separating each degree of polymerization. PEGs of average molecular weight>500 Da were detected from particles that also contained the tripeptide tyrosine-tyrosine-tyrosine or 2,5-dihydroxybenzoic acid, which were added to nebulized solutions to act as matrices to assist LDI using pulsed 266 nm and 355 nm lasers, respectively. Experiments were performed on two aerosol mass spectrometers, one reflectron and one linear, that each utilize two time-of-flight mass analyzers to detect positive and negative ions created from a single particle. PEG-containing particles are currently being employed in the optimization of our bioaerosol mass spectrometers for the application of measurements of complex biological samples, including human effluents, and we recommend that the same strategies will be of great utility to the development of any online aerosol LDI mass spectrometer platform.     

Synthesis of micrometer-sized silica-stabilized polystyrene latex particles

Micrometer-sized silica-stabilized polystyrene latexes have been readily prepared by alcoholic dispersion polymerization using a 13 or 22 nm commercial alcoholic silica sol as the sole stabilizing agent. These resulting surfactant-free polystyrene particles have relatively narrow particle size distributions and contain surprisingly low levels of silica (相似文献   

Synthesis and characterization of polychloromethylstyrene nanoparticles of narrow size distribution by emulsion and miniemulsion polymerization processes

Polychloromethylstyrene nanoparticles of sizes from 12.0 ± 2.3 to 229.6 ± 65 nm were prepared by the emulsion and miniemulsion polymerization of chloromethylstyrene in an aqueous continuous phase in the presence of potassium persulfate as initiator, sodium octylbenzenesulfonate as surfactant, and hexadecane as costabilizer for the miniemulsion polymerization process only. The influence of various polymerization parameters (e.g., concentration of the monomer, initiator, the crosslinker monomer, and the surfactant) on the properties of the particles (e.g., size, size distribution, and yield) has been elucidated. The polychloromethylstyrene nanoparticles formed via the emulsion polymerization mechanism possess smaller diameter and size distribution than those formed under similar conditions via the miniemulsion polymerization mechanism. Other differences between these two polymerization mechanisms have also been elucidated. For future study, we wish to use these nanoparticles for the covalent immobilization of bioactive reagents such as proteins to the surface of these nanoparticles for various biomedical applications.     

Preparation of micrometer-sized poly(methyl methacrylate) particles with amphoteric initiator in aqueous media

A previously proposed method based on soap-free emulsion polymerization with an amphoteric initiator for producing micrometer-sized polystyrene particles was extended to application with methyl methacrylate (MMA). The aggregation and dispersion stability of polymer particles, which have ionizable groups arising from initiator radicals, can be controlled by adjusting the pH of the reaction system accompanied with the addition of ionic monomer. Polymerizations were carried out with 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] tetrahydrate amphoteric initiator, NH(3)/NH(4)Cl pH buffer, and sodium p-styrenesulfonate anionic monomer (NaSS) in ranges of MMA concentration (0.58-2.32 kmol/m(3) H(2)O) and NH(3) concentration (2.5-20 mol/m(3) H(2)O) at fixed concentrations of 5 mol/m(3) H(2)O initiator, 10 mol/m(3) H(2)O NH(4)Cl, and 1 mol/m(3) H(2)O NaSS at 65 degrees C. The addition of NaSS during the polymerization could improve stability in dispersion of particles, which coagulated in the absence of NaSS after the disappearance of monomer drops. An increase in the monomer concentration in the present method could enlarge the particle size without lowering the monodispersity of the particle size distribution. On the other hand, an increase in NH(3) concentration decreased the particle size. The highest monodispersity of particle sizes was obtained at a NH(3) concentration of 5 mol/m(3) H(2)O, which gave an average size of 1.5 microm and a coefficient of variation of particle size distribution of 2.2% that was much smaller than the standard criterion for monodispersity, 10%.     

Synthesis and characterization of novel core-shell colloidal particles ZnO/poly(ethylcyanoacrylate)

Here we report the synthesis and physicochemical characterization of novel hybrid core/shell type ZnO/poly(ethylcyanoacrylate) colloidal particles. It is expected that coating ZnO colloidal particles with biocompatible and biodegradable poly(alkylcyanoacrylates) will pave the way toward the potential application of ZnO colloidal particles in biomedical research. Recent findings of cell selective toxicity indicate a potential utilization of ZnO colloidal particles in the treatment of cancer. For this purpose, ZnO colloidal particles have to be selectively delivered to the site of action by a suitable biocompatible and biodegradable carrier system. Toward this goal, poly(alkylcyanoacrylates) meet ideally the requirements for carrier systems in drug delivery due to their biocompatibility, biodegradability, low toxicity, and ability to overcome the multidrug resistance in cancer cells.     

Preparation and characterization of core-shell polystyrene/polychloromethylstyrene and hollow polychloromethylstyrene micrometer-sized particles of narrow-size distribution

Polystyrene core microspheres of narrow-size distribution were prepared by dispersion polymerization of styrene in a mixture of ethanol and 2-methoxy ethanol. Polystyrene/polychloromethylstyrene and polystyrene/poly(chloromethylstyrene-divinylbenzene) core-shell microspheres of narrow-size distribution were prepared by seeded emulsion polymerization of chloromethylstyrene or chloromethylstyrene and divinylbenzene in the presence of the polystyrene core microspheres at 71 °C. Core-shell particles with different properties (size, surface morphology, and composition) have been prepared by changing various parameters belonging to the emulsion polymerization process, e.g., volume of the chloromethylstyrene and the volume ratio of chloromethylstyrene to divinylbenzene. Dissolution of the polystyrene core of the polystyrene/poly(chloromethylstyrene-divinylbenzene) core-shell particles resulted in the formation of crosslinked hollow polychloromethylstyrene microspheres, broken crosslinked polychloromethylstyrene shells, or particles containing voids, depending on the composition of the polystyrene/poly(chloromethylstyrene-divinylbenzene) particles.     

Synthesis of high molecular weight and narrow molecular weight distribution poly(acrylonitrile) via RAFT polymerization

Well‐defined polyacrylonitrile (PAN) of high viscosity‐average molecular weight (M_η = 405,100 g/mol) was successfully synthesized using reversible addition‐fragmentation chain transfer polymerization. The polymerization exhibits controlled characters: molecular weights of the resultant PANs increasing approximately linearly with monomer conversion and keeping narrow molecular weight distributions. The addition of 0.01 equiv (relative to monomer acrylonitrile) of Lewis acid AlCl₃ in the polymerization system afforded the obtained PAN with an improved isotacticity (by 8%). In addition, the influence of molecular weights and molecular weight distributions of PANs on the morphology of the electrospun fibers was investigated. The results showed that, under the same conditions of electrospinning, average diameter (247–1094 nm) of fibers increased with molecular weights of PANs, and it was much easier to get “uniform” diameter fibers while using PANs with narrow molecular weight distributions as the precursor of electrospinning. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

One-pot, high-yield synthesis of size-controlled gold particles with narrow size distribution

Here, we first report a facile one-step one-phase synthetic route to achieve size-controlled gold micro/nanoparticles with narrow size distribution by using o-diaminobenzene as a reducing agent in the presence of poly(N-vinyl-2-pyrrolidone) via a simple wet-chemical approach. All experimental data including that from scanning-electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction techniques indicates that the gold micro/nanoparticles with a narrow size distribution were produced in high yield (approximately 100%).     

Synthesis and characterization of poly(tetrafluoroethyleneperoxides)

Tetrafluoroethylene (TFE) and oxygen react at low temperature in radical conditions to give perfluoropolyether-polyperoxide polymers. This oxypolymerization reaction has been applied on industrial scale for the manufacture of perfluoropolyethers, presently used in many application fields.It is known that highly unstable polymers containing large amounts of peroxidic units -CF₂CF₂OO- can be formed in particular conditions and may represent a potential hazard in the TFE oxypolymerization process. However little has been reported in the literature on the reaction conditions and the characterization of these polymers.In the present paper we describe the synthesis of perfluoropolyether-polyperoxide polymers with high peroxide content up to the nearly pure poly(perfluoroethyleneperoxide). The investigation is particularly focused to elucidate the relationship between reaction conditions, kinetics and polymer structure. The experimental results indicate that the physical chemical properties of these materials are strongly affected by the peroxide content, this latter depending on the reaction conditions, mainly TFE concentration and initiation rate.     

Synthesis and characterization of poly(amide-ureas)

Poly(amide-ureas) have been prepared by the action of di-isocyanates generated in situ, a technique so far not used for the preparation of poly(amide-ureas). The polymers were characterized by i.r., X-ray, thermal and viscosity measurements.     

Preparation of colored poly(styrene-co-butyl methacrylate) micrometer size beads with narrow size distribution by dispersion polymerization in presence of dyes

The preparation of monodisperse polymer particles formed by a dispersion copolymerization of a system containing styrene, butyl methacrylate, and nonpolymerizable dyes has been studied. Both the polarity of the ethanol–water dispersion medium and the polymerization rate were found to have a significant effect on the particle size. Experimental conditions have been determined that enable the preparation of colored beads having a narrow size distribution. While the benzoyl peroxide initiated polymerization is seriously inhibited by the presence of dyes, polymerization with azobisisobutyronitrile in presence of the black dye Nigrosin affords monodisperse beads in a high yield. © 1995 John Wiley & Sons, Inc.