Two-stage Dispersion Polymerization Research Articles

The preparation of novel AIE fluorescent microspheres by dispersion polymerization

ABSTRACT An approach to prepare monodisperse polystyrene microspheres with aggregation-induced emission (AIE) characteristics has been developed which shows promising applications in fluorescence-encoding. The micron-sized, monodisperse polystyrene microspheres with AIE molecules were perfectly synthesized by two-stage dispersion polymerization. Fluorescent AIE monomer was synthesized by Suzuki reaction, confirmed by nuclear magnetic resonance (NMR). These AIE fluorogens (AIEgens) exhibited unique properties such as bright green emission in solid state and increased emission in tetrahydrofuran (THF) solution with the increase of water content. The influence of the AIE molecules concentration to microspheres synthesis was well investigated. The reaction conditions were optimized to obtain the functional polystyrene microspheres with a size distribution around 3%. The novel microspheres were characterized by scanning electron microscopy (SEM), confocal fluorescence microscope and flow cytometry. According to these results, two-stage dispersion polymerization was proved to be an efficient pathway for the preparation of AIE fluorescent and functionalized microspheres, which could be used in many biomedical industries.

Development of Multiplexed Bead-Based Immunoassays for Profiling Soluble Cytokines and CD163 Using Mass Cytometry.

Bead-based immunoassays are multiparametric analysis allowing for the simultaneous quantification of a large number of biomarkers within a single sample. Mass cytometry is an emerging cytometric technique that offers a high multiplexing capacity in a high-throughput setting but has not yet been applied to bead-based assays. In this study, we developed a multiplex bead-based immunoassay of cytokines and CD163 designed for mass cytometry (MC). A set of 11 types of lanthanide-encoded microbeads were synthesized by two-stage dispersion polymerization as classifier candidates for the assay. These beads were then decorated with different Abs on the surface to capture the target cytokines in solution. Gold nanoparticles were employed as reporters to identify the binding of target cytokines on the classifier surface. As a proof-of-concept study, we first developed four-plex and nine-plex assays of mixtures of cytokines in standard solutions. The MC signal intensities of these immunoassays were responsive to the concentration differences in the standard solutions with high detection sensitivities at low analyte concentrations. Finally, we examined a sample of peripheral blood mononuclear cells (PBMCs) with the nine-plex assay, comparing an unstimulated sample with a sample stimulated to promote cytokine secretion.

One-pot synthesis of cross-linked nonspherical polystyrene particles via dispersion polymerization: the effect of polymerization conditions on the morphology of the particles

Herein we report the fabrication of cross-linked polystyrene particle with a variety of nonspherical morphologies such as red blood cell-like, cap-like, apple-like and so forth through two-stage dispersion polymerization in polar media. Furthermore, we examine the effect of different polymerization conditions including monomer and cross-linker concentration, and the type of initiator, monomer, stabilizer and cross-linker on the shape of the obtained particles. The acquired results reveal that the particles morphology can be altered from spherical to nonspherical with a decrease in the content of cross-linker and monomer, and using more reactive initiators and cross-linkers. Furthermore, particles shape can be changed through the addition of a different second-stage monomer type. Finally, the possible formation mechanism of the discussed nonspherical particles is illustrated.

Monodisperse polystyrene microspheres containing quaternary ammonium salt groups by two-stage dispersion polymerization: effect of reaction parameters on particle size and size distribution

A facile approach to prepare monodisperse polystyrene (PS) particles containing quaternary ammonium salts with long alkyl chain was reported. The PS particles containing quaternary ammonium salts are prepared by two-stage dispersion polymerization in ethanol/water (80/20 w/w) mixture with polyvinylpyrrolidone (PVP) as a steric stabilizer and fatty alcohol polyoxyethylene ether (AEO-9) as a co-stabilizer. Polymerizations are conducted using N′-dimethyl-N-n-dodecyl-N-2-methacryloyloxyethylammonium bromide (QDMDB) as a comonomer added in the second stage. We identify reaction conditions where one can obtain the functional polystyrene microspheres with a size distribution less than 3%. The influence of the initiator concentration, the styrene monomer concentration, the stabilizer concentration, and QDMDB comonomer concentration on the average particle size and the efficient of variation are investigated comprehensively. The novel particles are examined using scanning electron microscopy (SEM), gel permeation chromatography (GPC), zeta potential, and nuclear magnetic resonance (1H NMR). QDMDB comonomer not only functionalized the polystyrene particles but also proved to be effective in controlling the particle size and size distribution. According to these results, we show that two-stage dispersion polymerization is an effective pathway for the structure design of the functional microspheres.

Synthesis of Controllable Carboxylated Polystyrene Microspheres by Two-Step Dispersion Polymerization with Hydrocarbon Alcohols

Carboxylated polystyrene (PS) microspheres were synthesized by the two-step dispersion polymerization of styrene in hydrocarbon alcohols (CnH2n+1OH,n=1–5) in the presence of acrylic acid (AA) as a functional comonomer, 2,2′-azobis-(2-methylbutyronitrile) (AMBN) as the initiator and polyvinylpyrrolidone (PVP55) as the dispersant. The effects of solvent type, AA concentration, and first reaction time on the carboxyl content on the microsphere surfaces were investigated. The PS microspheres were characterized by scanning electron microscopy, infrared spectroscopy, nuclear magnetic resonance, and gel permeation chromatography. The results showed that the first reaction time of the two-stage dispersion polymerization had a great influence on the nucleation process, and appropriately prolonging the first-step reaction time had a great influence on the surface carboxyl content. The effect of the solvent on the surface carboxyl content of PS microspheres was significant. With n-butanol as the solvent, the carboxyl group content on the surface of the microspheres reached 57.05 mg/g.

Functional mesoporous carbon nanospheres: Effects of adding magnetic source during different stage

To solve the challenge of preparing magnetic mesoporous carbon nanospheres (MMCNs) with uniform and disperse particles, a series of MMCNs are achieved by a self-assembly procedure in one-pot aqueous solution. Impacts of magnetic source on the morphology and textural property of the as-synthesized MMCNs are systematically investigated by altering their adding time. An extended “two-stage dispersion polymerization” mechanism is employed to explain the formation of MMCNs. Interestingly, adding Fe3+ during the particle growing stage can obtain MMCNs-2, exhibiting uniform particle size, large specific surface area, high adsorption capacity and magnetic properties for improving the release of water-insoluble drugs such as Lovastatin (LOV).

Preparation of hollow porous molecularly imprinted polymers for N-nitrosamine adsorption

Novel hollow molecularly imprinted polymer (HMIPs) microspheres were synthesized via two-stage dispersion polymerization and swelling seed polymerization technique with nicotinamide (NAM) as the template molecule. Binding experiments showed that the HMIPs possessed excellent binding properties toward N-nitroamines, including fast mass transfer rate, and efficient adsorption performance with the adsorption capacity reaching up to 1.7mg/g, which was 3 times higher than that of hollow non-imprinted polymers (HNIPs). The fast binding kinetics for one N-nitrosamine (4-(methylnitrosamino)-1-(3-pyridine)-1-butanone, NNK) was attributed to the hollow porous structure with the imprinted cavities on both external and internal surface of the HMIPs.

Synthesis of highly carboxylated monodisperse polystyrene microspheres by dispersion polymerization in fluorinated alcohol

Fluorinated alcohol is demonstrated as a suitable medium for the preparation of monodisperse carboxylfunctionalized microspheres by dispersion polymerization. In the presence of polyvinylpyrrolidone as stabilizer, coagulum-free monodisperse micrometer-sized copolymers containing up to 30 wt% acrylic acid could be produced via one-stage batch dispersion polymerization with 2,2,2-trifluoroethanol as the medium. The coefficient of variation for the particle size distribution decreased as the acrylic acid content in the monomers increased and stabilized at approximately 3% when the acrylic acid content was 15 wt% or higher. The resulting microspheres exhibited pHsensitive behavior. Dissolution of the copolymer chains in alkaline solution could be reduced by incorporating a cross-linkable comonomer. The monodispersity and colloidal stability of the carboxyl-functionalized microspheres were preserved until the amount of divinylbenzene reached 2 wt% based on the monomer. It was found that two-stage semi-continuous dispersion polymerization was an effective method for the synthesis of cross-linked carboxyl-functionalized microspheres.

Synthesis of polymeric core/shell microspheres with spherical virus-like surface morphology by Pickering emulsion

Abstract Core–shell polymeric microspheres of tens microns in size with perfect spherical virus-like surface morphology were prepared through Pickering emulsion polymerization. Pickering stabilizer, monodisperse Poly(Glycidyl methacrylate) (PGMA) microsphere were obtained by two-stage dispersion polymerization and acid catalyzed hydrolysis was employed to transform the epoxy groups into glycol groups, rendering the P(GMA) microspheres moderately hydrophilic to stabilize Pickering emulsion. The P(GMA) microspheres and core–shell microspheres were characterized by scanning electronic microscope(SEM), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering(DLS). The results show that monodisperse P(GMA) microspheres were arrayed in a compact hexagonal arrangement on the surface of core–shell microspheres, forming a perfect spherical virus-like surface morphology.

Blue, green, and orange-red emission from polystyrene microbeads for solid-state white-light and multicolor emission.

Solid-state white-light emission was achieved from polystyrene (PS) microbeads incorporated with fluorophores based on perylene bisimide (PBITEG) and oligo(p-phenylenevinylene) (OPV) as acrylic cross-linkers. The PS beads incorporated with only PBITEG gave intense orange-red emission; PS incorporated with OPV exhibited blue-emission, whereas a series of polymers incorporating both cross-linkers exhibited varying shades of white-light emission. One of the PS samples, PS-PBITEG-6.25-OPV-4.28 (PBITEG incorporation: 6.25 × 10(-7) mole; OPV incorporation: 4.28 × 10(-7) mol), exhibited pure white-light emission in the powder form with CIE coordinates (0.33, 0.32). The rigid aromatic cross-linkers were incorporated into the PS backbone in a two-stage dispersion polymerization to afford PS beads in the size range 2 to 3 μm. The incorporation of fluorophores as cross-linkers enabled covalent attachment of the dye to the polymer backbone, avoiding dye leakage besides avoiding aggregation-induced fluorescence quenching.

Fluorescent Cross-Linked Polystyrene Perylenebisimide/Oligo(p-Phenylenevinylene) Microbeads with Controlled Particle Size, Tunable Colors, and High Solid State Emission

A series fo cross-linked fluorescent polystyrene (PS) microbeads with narrow size distribution and intense solid state emission was developed. Fluorophores based on perylene bisimide (PBI) and oligo(p-phenylenevinylene) (OPV) designed as acrylic cross-linkers were introduced into the polymerization recipe in a two-stage dispersion polymerization, carried out in ethanol in the presence of poly(vinylpyrrolidone) (PVP) as stabilizer. The structural design permitted introduction of up to 10(-5) moles of the fluorophores into the polymerization medium without fouling of the dispersion. The particle size measured using dynamic light scattering (DLS) indicated that they were nearly monodisperse with size in the range 2-3 μm depending on the amount of fluorophore incorporated. Fluorescence microscope images of ethanol dispersion of the sample exhibited intense orange red emission for PS-PBI-X series and green emission for PS-OPV-X series. A PS incorporated with both OPVX and PBIX exhibited dual emission upon exciting at the OPV wavelength of 350 nm and PBI wavelength of 490 nm, respectively. The low incorporation of fluorophore resulted in almost complete absence of aggregation induced reduction in fluorescence as well as red-shifted aggregate emission. The solid state emission quantum yield measured using integrating-sphere setup indicated a very high quantum yield of ϕpowder = 0.71 for PS-OPV-X and ϕpowder = 0.25 for PS-PBI-X series. The cross-linked PS microbeads incorporating both OPV and PBI chromophores had a ϕpowder = 0.33 for PBI emission and ϕpowder = 0.20 for OPV emission. This strategy of introducing fluorophore as cross-linkers into the PS backbone is very versatile and amenable to simultaneous addition of different suitably designed fluorophores emitting at different wavelengths.

Synthesis of poly(N-isopropylacrylamide) particles for metal affinity binding of peptides

Temperature-sensitive poly(N-isopropylacrylamide) (PNIPAM) microgel particles with metal affinity ligands were prepared for selective binding of peptides containing the His6-tag (six consecutive histidine residues). The PNIPAM particles were copolymerized with the functional ligand vinylbenzyl iminodiacetic acid (VBIDA) through a two-stage dispersion polymerization using poly(N-vinyl pyrrolidone) (PVP) as a steric stabilizer. The resulting particles were monodisperse in size and colloidally stable over a wide range of temperature and ionic strength due to chemically grafted PVP chains. The particle size was also found to be sensitive to ionic strength and pH of the aqueous environment, likely due to the electrostatic repulsion between ionized VBIDA groups. Divalent nickel ions were chelated to the VBIDA groups, allowing selective metal affinity attachment of a His6-Cys peptide. The peptide was released upon the addition of the competitive ligand imidazole, demonstrating that the peptide attachment to the particles is reversible and selective.

Surface functionalization of cross-linked polystyrene microspheres via thiol–ene “click” reaction and assembly in honeycomb films for lectin recognition

Abstract

Gold-nanoparticle coated La, Tb-encoded PS beads and their application in investigating the performance of the inductively coupled plasma of a mass cytometer

We describe the preparation of La, Tb-encoded-AuNP-coated PS microbeads via the combination of two-stage dispersion polymerization and post-functionalization of the particle surface. The introduction of La and Tb ions into the beads was achieved by the addition of LnCl3 and TbCl3 salts along with acrylic acid in the second the stage of dispersion polymerization. After the coating the surface of the beads with a silica layer containing methacrylate functional groups, a poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) layer was introduced by free radical polymerization. Subsequently, the PDMAEMA layer hosted the formation of gold nanoparticles on the surface of the beads. The formation of gold nanoparticles (AuNPs) on the surface of the beads was confirmed by dark-field transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy (EDX) and mass cytometry. Release experiments showed a negligible loss of Au ions or gold nanoparticles in 1.0% HCl aqueous solution over a two week period. The La, Tb-encoded-AuNP-coated PS beads were used to investigate the influence of plasma conditions on the thermolytic breakdown, diffusion, and matrix effects in the mass cytometer having two “thermometer” elements La (imbedded in the bulk of the bead) and Au (located on the bead surface). These experiments defined optimum conditions in terms of uniform ionization of the Au atoms present in the AuNPs. They also showed that neither the carbon-rich PS matrix nor the thin silica coating of the 1.6 μm diameter PS particles influenced the ability of the mass cytometer to determine La and Tb ion content quantitatively.

The synthesis and characterization of lanthanide-encoded poly(styrene-co-methacrylic acid) microspheres

Lanthanide-encoded polystyrene microspheres with methacrylic acid (MAA) as a co-monomer and with diameters on the order of 2 μm and a very narrow size distribution were synthesized by two-stage dispersion polymerization (2-DisP). These microspheres were designed as a platform for mass cytometry-based bioassays. Different lanthanides (Ln) were loaded into these microspheres during the synthesis, through the addition of LnCl3 salts and excess MAA to the reaction after about 10% conversion of styrene, i.e., well after the microsphere nucleation stage was complete. Different levels of MAA were employed to investigate the relationship between the number of carboxyl group on the particle surface and the amount of MAA used. The reaction remained well controlled with both 2 and 4 wt % MAA. As monitored by inductively coupled plasma (ICP) mass spectrometry, we found high incorporation efficiency (>95%) of Ln ions into the particles when the total amount of LnCl3 salts in the reaction mixture was sufficiently small. The Ln incorporation efficiency decreased with the increasing amount of LnCl3 salts. Mass cytometry analysis shows that individual microspheres contain ca. 105–108 chelated lanthanide ions, either a single element or a mixture of elements. This method of incorporating lanthanide into P(S-MAA) particles through the second stage of two-stage dispersion polymerization yields microspheres suitable for the highly multiplexed detection of biomolecules.

Color-tuned FRET polystyrene microspheres by single wavelength excitation

Fluorescent monodisperse polystyrene microspheres were prepared by two-stage dispersion polymerization, which successfully covalently labeled microspheres with two dyes without disturbing the final particle size and size distribution. By varying the dye concentrations, microspheres show tuned colors with different fluorescent intensity under a single wavelength excitation. Fluorescence resonance energy transfer (FRET) between two labeled dyes was proved to contribute to the emission of the longer-wavelength dye at a shorter-wavelength excitation. There is no dye leakage for microspheres because of the covalent incorporation of dye molecules. The microsphere matrix provides good protection of dye molecules and blocks the influence of media outside on the fluorescence of microspheres. Single microsphere shows intense fluorescence due to a large number of encapsulated dye molecules. These uniform barcoding fluorescent microspheres have potential application in multiplexed bioanalysis.

Dual-color polystyrene microspheres by two-stage dispersion copolymerization

Dual-color monodisperse polystyrene microspheres have been prepared by two-stage dispersion polymerization, whose addition of the dye-comonomer was deferred until the nucleation stage was complete. Two dyes were covalently incorporated into microspheres by copolymerization without disturbing the final particle size and size distribution. No dye leakage occurs for the microsphere suspension because of covalent bonding of dye molecules. By varying the dye concentrations in microspheres, we obtained fluorescent microspheres with two distinguishing parts of fluorescence and varied fluorescent intensity ratios under a single-wavelength excitation. The microspheres present intense fluorescence for the large amount of encapsulated dye molecules.

Preparation of highly crosslinked monodisperse poly(styrene-co-divinylbenzene) microspheres by two-stage dispersion polymerization

Monodisperse poly(styrene-co-divinylbenzene) microspheres crosslinked with different concentrations of divinylbenzene were synthesized by two-stage dispersion polymerization in ethanol dispersion medium with poly(N-vinyl pyrrolidone) as a stabilizer and 2,2′-azobisisobutyronitrile as a radical initiator. The microsphere size, size distribution, surface morphology, and structure were characterized by a particle analyzer, a scanning microscope and IR spectroscopy. The effect of the adding time, the adding rate, and the concentration of crosslinker on the size, size distribution, and shape of the resulting particles were also investigated. Highly crosslinked monodisperse microspheres with diameters from 2 to 4 μm were obtained. The SEM characterization showed that the resulting microspheres had spherical shapes with smooth surfaces. The obtained microspheres have good resistance to solvent whether at ambient or heating temperatures and are thermally stable. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Monodisperse Micrometer-Size Carboxyl-Functionalized Polystyrene Particles Obtained by Two-Stage Dispersion Polymerization

Monodisperse carboxylated micrometer-sized polystyrene particles were synthesized by dispersion polymerization of styrene in ethanol and in 95% ethanol−water in the presence of acrylic acid (AA) as a functional comonomer. When AA was present at the onset of the reaction, the resulting particles had an increased particle size and a broader size distribution than those prepared in the absence of AA. If, however, the addition of AA was delayed ca. 1 h, so that the particle nucleation stage was complete, then 2 wt % AA, dissolved in monomer plus solvent, could be added to the reaction without a deleterious effect on particle formation. When larger amounts of AA (e.g., 4 wt % based on styrene) were added, most resulting particles became unstable and coagulated if PVP55 (Mw ≈ 55000) was used as the stabilizer. Some evidence points to interaction between −COOH groups on the particles as the origin of particle aggregation. Improved colloidal stability was achieved by decreasing the solids content, increasing the polarity of the medium, and switching to PVP360 (Mw ≈ 360000) as the polymeric stabilizer. Coagulum-free particles with a very narrow size distribution containing 2%, 4%, and 6 wt % AA could be obtained in this way. Under these conditions, adding different amounts of AA in the particle growth stage did not change the particle size or size distribution.

Monodisperse, micrometer-sized low molar mass polystyrene particles by two-stage dispersion polymerization

Free-radical dispersion polymerization of styrene was carried out in ethanol and in ethanol–water mixtures in the absence and presence of carbon tetrabromide (CBr4) as a chain transfer agent. When CBr4 was present at the onset of the reaction, particles with a broad size distribution were obtained. If, however, the addition of CBr4 was delayed ca 1h, so that the particle nucleation step was complete, then 1–2wt% chain transfer agent, dissolved in monomer plus solvent, could be added to the reaction without a deleterious affect on particle formation. The particle size and size distribution was essentially identical to that obtained in the absence of CBr4. When more CBr4 was added, other problems arose. These problems appeared to be due to solubility of low molar mass polymer in the reaction medium. They could be overcome by running the reaction in ethanol–water mixtures (e.g. 5wt% water) to decrease the solubility of oligo-styrene at 70°C, the reaction temperature. In this way, monodisperse particles could be prepared in the presence of 3wt% CBr4 based upon total styrene, consisting of polymers with Mn=7060, Mw/Mn=2.4.