Dispersion Polymerization Of Styrene Research Articles

The effect of polystyrene-block-poly(4-vinylpyridine) prepared by a RAFT method in the dispersion polymerization of styrene

The dispersion polymerization of styrene has been carried out using polystyrene-block-poly(4-vinylpyridine) copolymer [P(S-b-4VP)], prepared by a reversible addition-fragmentation chain transfer (RAFT) method, as a steric stabilizer in alcohol media. These block copolymer contains a long poly(4-vinylpyridine) block and a short polystyrene block. The stable spherical particles were obtained when the block copolymer concentrations increased from 2 to 20 wt.% relative to the monomer and the average particle sizes decreased from 340 to 200 nm with increasing concentration of the block copolymer. Alcoholic solvents, from methanol to n-hexanol, are responsible for the particle size. These results indicate that the poly(S-b-4VP) block copolymer is effective for providing polystyrene nano-sized particles with a low content of it working as a good stabilizer in any kind of alcoholic medium.

Synthesis and characterization of spherical and hemispherical polyepoxide micrometer‐sized particles of narrow size distribution by a single‐step swelling of uniform polystyrene template microspheres with glycidyl methacrylate

AbstractPolystyrene template microspheres of narrow size distribution were prepared by dispersion polymerization of styrene in a mixture of ethanol and 2‐methoxy ethanol. Spherical and hemispherical polystyrene/poly(glycidyl methacrylate) microspheres of narrow size distribution were prepared by a single‐step swelling of the polystyrene template microspheres with the swelling solvent monomer glycidyl methacylate, followed by polymerization of the monomer within the swollen template microspheres at 73 °C. Uniform polystyrene/poly(glycidyl methacylate‐ethylene glycol dimethacrylate) polyepoxide composite microspheres were synthesized similarly, substituting glycidyl methacylate for glycidyl methacylate and ethylene glycol dimethacrylate. Uniform crosslinked poly(glycidyl methacylate‐ethylene glycol dimethacrylate) polyepoxide microspheres have been prepared by dissolution of the PS template polymer of the former composite microspheres. Particles with different properties, for example size, size distribution, shape, surface morphology, surface area, and so forth, were prepared by changing various parameters belonging to the swelling and/or polymerization steps, for example, volume of the swelling monomer/s and/or the swelling solvent dibutyl phthalate. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4612–4622, 2007

Factors influencing magnetic polymer microspheres prepared by dispersion polymerization

AbstractMagnetic iron oxide (Fe3O4) was prepared by a coprecipitation method. Core–shell composite magnetic polymer microspheres with carboxyl groups were synthesized by the dispersion polymerization of styrene and acrylic acid in the presence of magnetic oxide, and dibenzoyl peroxide was used as an initiator. The synthesized magnetic polymer microspheres were characterized with X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and so forth. The results indicated that the product was single‐phase Fe3O4, and its average size was about 10 nm. The configuration of the microspheres, which contained carboxyl groups, was spherical, and the average size was about 2 μm. The results of vibrating sample magnetometry tests showed that the magnetic powders produced by different surfactants had different saturation magnetizations. When poly(ethylene glycol) with a weight‐average molecular weight of 4000 was used as a surfactant, the saturation magnetization of the samples reached 69.2 emu/g. The factors that affected the shape, magnetism, size, and distribution of the microspheres were also studied. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Evolution of Core-Shell Structure Using Functional Polystyrene and Gold

A core-shell of a carboxylic functional polystyrene (PS-COOH) with gold was prepared by the combination of surface gold-seeding and subsequent shell growth in a gold solution. The PS-COOH cores were prepared by a dispersion polymerization of styrene for seed formation followed by copolymerization of styrene and methacrylic acid. In the preparation of gold shell, PS-COOH cores were initially immersed into gold nanoparticles containing solution and continuous gold shell was formed by employing a mixed aqueous solution of Au(OH)3 and NH2OH. The gold nanoparticles impregnated into the PS-COOH cores were used as gold seeds to form continuous gold shells. The characteristics of the PS-COOH/Au core-shells were investigated by SEM, TEM, EDS and XPS.

Suppression of Dioxin Emission in Co-Incineration of Poly(vinyl Chloride) with TiO2-Encapsulating Polystyrene

This paper presents an approach to the suppression of the emission of dioxin and its precursors as a result of the co-incineration of poly (vinyl chloride) (PVC) with TiO2-encapsulating polystyrene (TEPS), in which TiO2 nanoparticles with the capacity to adsorb dioxin and its precursors are encapsulated without significant agglomeration. Field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were used to show that spherical PS particles encapsulating a uniform dispersion of TiO2 nanoparticles are obtained through the dispersion polymerization of styrene in an aqueous ethanol medium. To facilitate the encapsulation, the surface of the TiO2 nanoparticles was modified with a polymerizable organic silane linker priorto polymerization. For comparison purposes, experiments were performed in which PVC was co-incinerated with neat PS (PVC/PS), TiO2-encapsulating PS (PVC/TEPS), and mechanically mixed TiO2/PS (PVC/PS-MTiO2). Qualitative and quantitative investigations of the suppression of the emission of a model dioxin and its precursors were performed by analyzing the exhaust gases from the co-incinerations using gas chromatography/ mass spectrometry (GC/MS). The results show that the addition of TiO2 nanoparticles into co-incineration systems reduces the concentration of the dioxin and its precursors in exhaust gases. Moreover, the quantitative removal efficiencies for PVC/TEPS and PVC/PS-MTiO2 indicate that the suppression is successfully enhanced by the TiO2-encapsulation: increases in the dispersity of the nanoparticles result in improved adsorption of the dioxin and its precursors.

Dispersion polymerization of styrene in supercritical CO 2 stabilized by random copolymers of 1 H,1 H-perfluorooctyl methacrylate and 2-dimethylaminoethyl methacrylate

The dispersion polymerizations of styrene in supercritical CO 2 employing random copolymers composed of 1,1-dihydroperfluorooctyl methacrylate (FOMA) and 2-dimethylaminoethyl methacrylate (DMAEMA) (poly(FOMA- co-DMAEMA)) as stabilizers were investigated with two different compositions. It was demonstrated that micron-sized, free-flowing, spherical polystyrene (PS) particles could be obtained in high yields by poly(FOMA- co-DMAEMA) containing as low as 50% (w/w) FOMA. Results indicate that DMAEMA units in the stabilizer, as an anchor group with its special characteristics, can be adsorbed on PS particles to provide an enough colloidal stability. The initial concentration of styrene and the stabilizer affected the molecular mass, polymerization yield, and the morphology of PS particles. The PS particles could be redispersed in buffered water (pH 2.1) by an ionic stabilization mechanism provided by DMAEMA units on the surface. Dynamic light scattering (DLS) measurements of aqueous latexes gave similar particle sizes as those from SEM analysis.

Dispersion polymerization of styrene in supercritical CO 2 in the presence of non-fluorous random copolymeric stabilizers

The non-fluorous random copolymers, poly (3-[tris(trimethylsilyloxy)silyl]propyl methacrylate- co-2-dimethylaminoethyl methacrylate) (poly(SiMA- co-DMAEMA)) and poly (3-[tris(trimethylsilyloxy)silyl]propyl methacrylate- co-diisopropylaminoethyl methacrylate) (poly(SiMA- co-DPAEMA)) were prepared with different comonomer compositions and utilized as stabilizers in the dispersion polymerization of styrene in supercritical carbon dioxide (scCO 2). The copolymers were found to provide an effective stabilization on the polystyrene (PS) latexes in scCO 2. Poly(SiMA- co-DMAEMA) (71:29) were proved to be optimal among (86:11), (71:29), and (57:33) comonomer compositions to produce micron-sized spherical PS particles with higher yields. Poly(SiMA- co-DPAEMA) having higher methyl branching in the DPAEMA pendant group provided a better stabilization compared to poly(SiMA- co-DMAEMA). The effect of varying concentration of stabilizer and monomer upon the polymerization yield, molar mass, and morphology of PS have been investigated.

Covalent immobilization of glucose oxidase onto poly(styrene-co-glycidyl methacrylate) monodisperse fluorescent microspheres synthesized by dispersion polymerization

In this study, micron-sized poly(styrene-co-glycidyl methacrylate) (PSt–GMA) fluorescent microspheres of 5.1 μm in diameter were synthesized via dispersion polymerization of styrene and glycidyl methacrylate in the presence of 1,4-bis(5-phenyloxazol-2-yl) benzene (POPOP), which provided surface functional groups for covalent immobilization of enzymes. In an effort to study the biocompatibility of the microspheres’ surface, glucose oxidase and β- d-(+)-glucose were selected as a catalytic system for enzymatic assays. A colorimetric method was adopted in evaluating enzymatic activity by introducing horseradish peroxidase (HRP). Both the immobilization amount and the apparent activity of immobilized glucose oxidase from Aspergillus niger (GOD) were determined at different conditions. The results show that the immobilized enzymes retained approximately 28 to 34% activity, as compared with free enzymes, without pronounced alteration of the optimum pH and temperature. Kinetics studies show that the corresponding values of K m and V max are 23.2944 mM and 21.6450 M/min · mg GOD for free enzymes and 35.1780 mM and 15.4799 M/min · mg GOD for immobilized enzymes. The operational stability studies show that immobilized GOD could retain nearly 50% initial activity after being washed 20 times. The results suggest that the resultant PSt–GMA fluorescent microspheres provide a suitable surface for covalent immobilizing biomolecules; therefore, they have the potential of being used in fluorescence-based immunoassays in high-throughput screening or biosensors.

Polystyrene−Silica Colloidal Nanocomposite Particles Prepared by Alcoholic Dispersion Polymerization

Micrometer-sized silica-stabilized polystyrene latex particles and submicrometer-sized polystyrene−silica nanocomposite particles have been prepared by dispersion polymerization of styrene in alcoholic media in the presence of a commercial 13 or 22 nm alcoholic silica sol as the sole stabilizing agent. Micrometer-sized near-monodisperse silica-stabilized polystyrene latexes are obtained when the polymerization is initiated with a nonionic AIBN initiator. These particles are stabilized by silica particles that are present on the latex surface at submonolayer concentration. The total silica content is no greater than 1.1 wt %, which corresponds to a silica sol incorporation efficiency of less than 1.3%. Reduction of the initial silica sol concentration led to a systematic increase in the mean latex diameter. In contrast, submicrometer-sized polystyrene-silica nanocomposite particles are obtained when the polymerization is initiated with a cationic azo initiator. The silica contents of these nanocomposite particles are significantly higher, ranging up to 29 wt %. Zeta potential measurements, XPS, and electron spectroscopy imaging by transmission electron microscopy (ESI/TEM) studies reveal a well-defined core−shell morphology for these particles, whereby the core is polystyrene and the shell comprises the silica sol. After calcination, these nanocomposite particles can form hollow silica capsules. Variation of the initial silica sol and initiator concentration has relatively little effect on the final particle size and silica content of these polystyrene−silica nanocomposite particles, but indicates silica sol incorporation efficiencies up to 72%.

Preparation of polystyrene/poly (4-butyltriphenylamine) composite particles by chemical oxidative seeded dispersion polymerization

Polystyrene (PSt)/poly (4-butyltriphenylamine; PBTPA) composite particles was prepared by a chemical oxidative seeded dispersion polymerization of (4-butyltriphenylamine) with PSt seed particles that were prepared by nonaqueous dispersion polymerization of styrene. Monodisperse composite particles were obtained when the ratio of monomer to seed, the rate of monomer feed, and poly(N-vinyl pyrrolidone; PVP) concentration was appropriately selected. The introduction of PBTPA was confirmed by the presence of the characteristic absorption band attributed to PBTPA from a Fourier transform infrared spectra. The solvent extraction with ethyl acetate revealed that composite particles consisted of PSt core and PBTPA shell. Then two-dimensional arrays of composite particles were also fabricated.

Synthesis of polystyrene microspheres by dispersion polymerization using poly(vinyl alcohol) as a steric stabilizer in aqueous alcohol media

Dispersion polymerization of styrene was investigated using PVA as a steric stabilizer in aqueous alcoholic media. In aqueous methanol and alcohol media, colloidally stable monodisperse polystyrene microspheres are synthesized using BPO and AIBN as initiators and various PVA concentrations of 0.5–10 wt.% relative to styrene. The effect of PVA on the size variation is found to be similar to that of conventional stabilizer, PVP. The yield of polymerization is significantly influenced by the amount of PVA. When initiator is changed to AIBN, the yield of polymerization is substantially lower than the BPO systems. Both chemical grafting and physical adsorption of PVA endow stability of the polystyrene particles. Such a mechanism was justified from the FT-IR spectrum of polystyrene particles in which characteristic peaks of PVA molecules are witnessed. The molecular weight increases with the PVA content due to the reduced particle size. The glass transition temperatures of the polystyrene particles lie in 98.9–104.4 °C regardless of PVA concentrations. Contrary to PMMA dispersion polymerization with a PVA stabilizer, no discernable change in the glass transition temperature is observed.

Reaction and stabilizing mechanism of the cross-type macromonomers in the dispersion polymerization of styrene

The cross-type (C-VUM) and linear-type (L-VUM) bifunctional vinyl urethane macromonomers and polystyrene (PS) using these macromonomers were synthesized in the dispersion polymerization in ethanol, and the reaction and stabilizing mechanism of the macromonomers was proposed. The structural verification of the macromonomers and PS was studied using 1H NMR. The weight-average particle size of C-PS (PS prepared with C-VUM) and L-PS (PS prepared with L-VUM) decreased from 4.41 to 1.36 μm and from 3.56 to 1.52 μm, whereas the average-molecular weight of those increased from 34,100 to 100,500 g/mol and from 32,200 to 71,800 g/mol, respectively. The XPS result showed that the C-PS was anchored with a larger amount of PEG than that of the L-PS on the particle surface. Thus, the reaction and stabilizing mechanism of the macromonomers for the formation of PS particles is proposed as the following. The particle surface of the C-PS is surrounded by a large amount of tail shaped macromonomers leading to higher molecular weights and smaller particle sizes. On the other hand, the particle surface of the L-PS is comprised of relatively small amounts of loop shaped macromonomers inducing lower molecular weights and larger particles of L-PS than C-PS.

Influence of a reversible addition–fragmentation chain transfer agent in the dispersion polymerization of styrene

AbstractDispersion polymerization was applied to the controlled/living free‐radical polymerization of styrene with a reversible addition–fragmentation chain transfer (RAFT) polymerization agent in the presence of poly(N‐vinylpyrrolidone) and 2,2′‐azobisisobutyronitrile in an ethanol medium. The effects of the polymerization temperature and the postaddition of RAFT on the polymerization kinetics, molecular weight, polydispersity index (PDI), particle size, and particle size distribution were investigated. The polymerization was strongly dependent on both the temperature and postaddition of RAFT, and typical living behavior was observed when a low PDI was obtained with a linearly increased molecular weight. The rate of polymerization, molecular weight, and PDI, as well as the final particle size, decreased with an increased amount of the RAFT agent in comparison with those of traditional dispersion polymerization. Thus, the results suggest that the RAFT agent plays an important role in the dispersion polymerization of styrene, not only reducing the PDI from 3.34 to 1.28 but also producing monodisperse polystyrene microspheres. This appears to be the first instance in which a living character has been demonstrated in a RAFT‐mediated dispersion polymerization of styrene while the colloidal stability is maintained in comparison with conventional dispersion polymerization. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 348–360, 2007

Latex and Hollow Particles of Reactive Polypyrrole: Preparation, Properties, and Decoration by Gold Nanospheres

Polypyrrole-coated polystyrene latex particles bearing reactive N-amino functional groups (PS-PPyNH2) were prepared by the in-situ copolymerization of pyrrole (Py) and the active amino-functionalized pyrrole (PyNH2) in the presence of 1.33 microm-diameter polystyrene (PS) latex particles. These particles were prepared by dispersion polymerization of styrene using poly(N-vinylpyrrolidone), PNVP, as a steric stabilizer. The functionalized polypyrrole-coated PS particles (PS-PPyNH2) were characterized in terms of their particle size and surface morphology using transmission electron microscopy (TEM). Infrared and X-ray photoelectron spectroscopy (XPS) detected pyrrole-NH2 repeat units at the surface of the latex particles, indicating that this monomer had indeed copolymerized with pyrrole. The core-shell structure of the PS-PPyNH2 particles was confirmed by etching the polystyrene core in THF, leading to the formation of hollow conducting polymer capsules. The PS-PPyNH2 particles were then decorated with citrate-stabilized gold nanoparticles via electrostatic interactions. Furthermore, etching of the polystyrene core resulted in the formation of gold-decorated PPyNH2 hollow capsules.

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.

Preparation of Polystyrene-Polyimide Particles by Dispersion Polymerization of Styrene Using Poly(amic acid) as a Stabilizer

Dispersion polymerization of styrene (S) and a cationic comonomer, 4-(vinylbenzyl)trimethylammonium chloride (VBA) was conducted in alkaline aqueous ethanol using various aromatic poly(amic acid)s (PAA) as stabilizers. The monodisperse particles were obtained in high yield using the optimum composition of solvent mixture depending on the PAA structure. By using a cationic comonomer (VBA), PAA was incorporated quantitatively into the particles. On the other hand, using cationic methacrylates as a comonomer, PAA was not incorporated effectively. The imidization of PAA on the particles proceeded with acetic anhydride and 4-(dimethylamino)pyridine to form PS-polyimide (PS-PI) particles. The PS-PI particles were maintained in spherical shape by the thermal treatment up to 240 °C. PI hollow particles were also obtained by washing PS-PI particles with toluene.

Synthesis and Characterization of Air-Stable Iron Nanocrystalline Particles Based on a Single-Step Swelling Process of Uniform Polystyrene Template Microspheres

Polystyrene template microspheres of narrow size distribution were prepared by dispersion polymerization of styrene in a mixture of ethanol and 2-methoxy ethanol. These template particles dispersed in aqueous solution have been used for entrapping Fe(CO)5, by a single-step swelling process of methylene chloride emulsion droplets containing Fe(CO)5, within these particles. The influence of different swelling parameters, such as the volume ratio [CH2Cl2/[Fe(CO)5], on the size and size distribution of the swollen template particles was elucidated. Air-stable Fe/Fe3C nanocrystalline particles have been prepared by thermal decomposition of the Fe(CO)5 swollen template particles at 600 °C in an inert atmosphere. Characterization of these air-stable Fe/Fe3C nanocrystalline particles has been accomplished by light microscopy, TEM, XRD, TGA, XPS, elemental analysis, and magnetic susceptibility measurements. These nanocrystalline particles have a core−shell structure where a coating of Fe3C and carbon protects the core body-centered cubic Fe from oxidation.

TEMPO‐mediated dispersion polymerization of styrene in the presence of camphorsulfonic acid

AbstractThe TEMPO‐mediated polymerization of styrene in the presence of camphorsulfonic acid (CSA) is carried out using controlled radical dispersion polymerization. In the absence of TEMPO and CSA, 92% of conversion was achieved within 3 h of polymerization. When TEMPO is solely used, broadening of particle size with narrow PDI was observed because of the prolonged polymerization time. However, when 1:1 molar ratio of CSA/TEMPO was added, the fairly monodisperse PS microspheres having 5.83 μm average size and 3.42% CV (coefficient of variation) were successfully achieved because of the narrow molecular weight of intermediate oligomers and shortening of the polymerization time. This result obviously indicates that the addition of CSA in TEMPO‐mediated dispersion polymerization not only shortens the polymerization time but also greatly improves the uniformity of the microspheres. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 62–68, 2006

Cross-Linked, Monodisperse, Micron-Sized Polystyrene Particles by Two-Stage Dispersion Polymerization

It is well-known that cross-linking agents such as divinylbenzene (DVB) interfere with the dispersion polymerization of styrene in ethanol, a reaction carried out in the presence of polymeric stabilizers such as poly(vinylpyrrolidone). Small amounts of DVB broaden the particle size distribution and lead to irregular particles, whereas modest amounts lead to coagulation. We report that many of these problems can be avoided if one delays the addition of the cross-linking agent until after the end of the nucleation stage of the reaction (e.g., at less than 5% monomer conversion). In this way one can obtain monodisperse polystyrene particles containing 1 wt % ethylene glycol dimethacrylate (EGDMA) as a cross-linker. A second set of problems arises if the cross-linking agent is consumed too early in the reaction, presumably because early network formation limits the swellability of the growing particles. These problems can be overcome by feeding DVB into the reaction over 12 h or by adding EGDMA in successive batches over 6 h. In this way, monodisperse particles with micrometer diameters, and a coefficient of variation of 2% or less, can be obtained containing up to 6 wt % cross-linker based on styrene.

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 °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 °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.