Emulsifier-free Emulsion Polymerization Of Styrene Research Articles

Construction of insulating layers on conductive nickel-plated core particles by thermal fusion of heterocoagulated polymer shell particles

In this study, we developed a method for fabricating conductive particles with an insulating layer on the surface, which can be applied to anisotropic conductive films. Core-shell particles were prepared from conductive nickel-plated core particles and positively charged polystyrene (PSt) shell particles carrying phosphonium groups on their surface by the heterocoagulation technique. The effect of alkyl chain lengths (ethyl, n-butyl, and n-octyl) of (4-vinylbenzyl)trialkylphosphonium chloride on the interfacial properties was investigated by surface tension measurement. Monodisperse PSt shell particles with a controlled particle size were successfully synthesized by emulsifier-free emulsion polymerization of styrene, (4-vinylbenzyl)triethylphosphonium chloride, and n-butyl acrylate. The effects of stirring time, temperature, NaCl concentration, and PSt shell particle concentration on heterocoagulation between the nickel-plated core particles and PSt shell particles were investigated. Uniform core-shell particles with a coverage of 60% could be prepared even though the heterocoagulation temperature was below the glass transition temperature and the NaCl concentration was below the critical coagulation concentration of the PSt shell particles. When the core-shell particles obtained through the heterocoagulation process were heated above the glass transition temperature of the shell particles for 6 h, a smooth polymeric insulating layer with melted shell particles was successfully formed on the surface of the nickel-plated core particles.

Self-assembly of polystyrene microspheres into two-level hierarchical structures

Two-level arrays of colloidal particles have been obtained using the method based on an intermittent, ‘‘stick–slip’’ motion of the meniscus during colloidal suspension evaporation. The ethanol suspension of monodisperse polystyrene microspheres of about 1 μm in size was prepared by emulsifier-free emulsion polymerization of styrene with potassium persulphate as an initiator. The resulting structures consist of parallel monolayer stripes of deposited microspheres, repeated with a period of 140–150 μm, and empty spaces between them. The microspheres are packed into a hexagonal structure inside the stripes. Laser diffraction patterns have been demonstrated for both levels of ordering, i.e., for the hexagonal structure at the first level and for the parallel stripes at the second level.

Preparation of polymer latex particles carrying salt-responsive fluorescent graft chains

We prepared the novel fluorescent polymer latex particles which can change their fluorescence intensity in response to the increasing NaCl concentration in water. Core polymer latex particles were synthesized by emulsifier-free emulsion polymerization of styrene and 2-(2-chloroisobutyroyloxy)ethyl methacrylate. Hydrophilic polymer chains containing epoxy groups were grafted from the core particles by surface-initiated atom transfer radical copolymerization of methoxy polyethyleneglycol methacrylate (MEOxMA, x = 4 or 9) and glycidyl methacrylate in aqueous media. After azidation of epoxy groups in graft chains, a water-soluble fluorescent dansyl derivative was successfully coupled with the graft chains by copper-catalyzed azide-alkyne cycloaddition in aqueous media. The wavelength of maximum fluorescence intensity of polymer particles carrying graft chains with longer PEG side chains (x = 9) was slightly blue-shifted (7 nm) and the fluorescence intensity increased (1.35 times) with an increase in NaCl concentration as opposed to polymer particles with shorter PEG chains (x = 4).

Copolymerization of styrene with N-vinylformamide and ethylene glycol dimethacrylate and characteristics of the formed particles

Emulsion and emulsifier-free emulsion polymerization of styrene, N-vinylformamide, and ethylene glycol dimethacrylate are investigated with the goal to form positively charged monodisperse submicron crosslinked particles. The effects of the monomer ratio, the type and concentration of the buffer salt, and the emulsifier concentration on the monomer conversion and on the shapes, size distributions, and surface characteristics of the formed particles are studied. It is shown that, in the surface layers, amino groups prevail over carboxylic groups. The total surface concentration of acidic and basic groups increases with the degree of crosslinking of particles and as a result of their subsequent surface hydrolysis.

Quantification of ATRP initiator density on polymer latex particles by fluorescence labeling technique using copper-catalyzed azide-alkyne cycloaddition

We developed a novel fluorescence labeling technique for quantification of surface densities of atom transfer radical polymerization (ATRP) initiators on polymer particles. The cationic P(St-CPEM-C4DMAEMA) and anionic P(St-CPEM) polymer latex particles carrying ATRP-initiating chlorine groups were prepared by emulsifier-free emulsion polymerization of styrene (St), 2-(2-chloropropionyloxy)ethyl methacrylate (CPEM), and N-n-butyl-N,N-dimethyl-N-(2-methacryloyloxy)ethylammonium bromide (C4DMAEMA). ATRP initiators on the surface of polymer particles were converted into azide groups by sodium azide, followed by fluorescent labeling with 5-(N,N-dimethylamino)-N′-(prop-2-yn-1-yl)naphthalene-1-sulfonamide (Dansyl-alkyne) by copper-catalyzed azide-alkyne cycloaddition (CuAAC). The reaction time required for both azidation of ATRP-initiating groups and successive fluorescence labeling of azide groups with Dansyl-alkyne by CuAAC were investigated in detail by FTIR and fluorescence spectral measurement, respectively. The ATRP initiator densities on the cationic P(St-CPEM-C4DMAEMA) and anionic P(St-CPEM) particle surfaces were estimated to be 0.21 and 0.15 molecules nm−2, respectively, which gave close agreement with values previously determined by a conductometric titration method. The fluorescence labeling through click chemistry proposed herein is a versatile technique to quantify the surface ATRP initiator density both on anionic and cationic polymer particles. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4042–4051

An experimental study on particle formation in emulsifier-free emulsion polymerization of styrene

Particle formation in polymerization of styrene induced within two stratified layers of a monomer and water containing an initiator was studied in the absence of emulsifiers and stirring. A polymerization-induced decrease of interfacial surface tension was observed. The particle size distribution was characterized by dynamic light scattering during polymerization. The results confirm particle nucleation through spontaneous emulsification process.

An Experimental Study on Particle Formation in Emulsifier-free Emulsion Polymerization of Styrene

An Experimental Study on Particle Formation in Emulsifier-free Emulsion Polymerization of Styrene

Preparation of titania hollow particles with independently controlled void size and shell thickness by catalytic templating core–shell polymer particles

Organic/inorganic hybrids were prepared by catalytic hydrolysis and subsequent polycondensation of tetra-n-butyl titanate (TnBT) in shell layers grafted on core particles. The core particles were synthesized by emulsifier-free emulsion polymerization of styrene, N-n-butyl-N-2-methacryloyloxyethyl-N,N-dimethylammonium bromide (C4DMAEMA), and 2-chloropropionyloxyethyl methacrylate using 2,2′-azobis(2-amidinopropane) dihydrochloride as an initiator. The core diameters were controlled in the range of 70–550 nm by adjusting a C4DMAEMA feed concentration. The core–shell particles were prepared by surface-initiated activator generated electron transfer–atom transfer radical polymerization of 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA). The sizes of core–shell particles were found to increase monotonically with an increase in a DMAEMA concentration. The hybrid particles were fabricated by adding TnBT into a water/ethanol dispersion of core–shell particles. The amounts of titania deposited increased in proportion to the grafted amounts of poly[2-(N,N-dimethylamino)ethyl methacrylate] on the core particles. The X-ray diffraction measurement revealed that the hollow titania particles obtained by heat treatment of hybrids have an anatase crystallographic phase.

A Thermo-Sensitive NIPA-Based Co-Polymer and Monosize Polycationic Nanoparticle for Non-viral Gene Transfer to Smooth Muscle Cells

Primary smooth muscle cells (SMC) isolated from the aorta of fetal calf were transfected with a green fluorescent protein (GFP)-encoding plasmid DNA, which was carried by a water-soluble and temperature-sensitive N-isopropylacrylamide-based (NIPAAm-based)-co-polymer, either poly(N-isopropylacrylamide-co-2-methacryloamidohistidine) (poly(NIPAAm-co-MAH)) or monosized PEGylated nanoparticle poly(styrene/poly(ethylene glycol) ethyl ether methacrylate/N-(3-(dimethylamino)propyl) methacrylamide) (poly(St/PEG-EEM/DMAPM)). Poly(NIPAAm-co-MAH) co-polymer was synthesized by solution polymerization of n-isopropylacrylamide (NIPAAm) and 2-methacrylamidohistidine (MAH). Monosized cationic nanoparticles were produced by emulsifier-free emulsion polymerization of styrene, PEG ethyl ether methacrylate and N-[3-(dimethyl-amino) propyl] methacrylamide, in the presence of a cationic initiator, 2,2-azobis (2-methylpropionamidine) dihydrochloride. The structure of poly(St/PEG-EEM/DMAPM) and poly(NIPAAm-co-MAH) was confirmed by1 H-NMR and FT-IR spectroscopy. Particle size/size distribution and surface charges of both carriers were measured by Zeta Sizer. The LCST behavior of poly(NIPAAm-co-MAH) co-polymer was followed spectrophotometrically. Poly(St/PEG-EEM/DMAPM) nanoparticles, with an average size of 78 nm and zeta potential of 54.4 mV, and an average size of 200 nm with a zeta potential of 54.2 mV, and poly(NIPAAm-co-MAH) were used in the transfection studies. The cytotoxicity of the vectors was tested using the MTT method. According to conditions for the transfection study (polymer/cell ratio and polymer–cell incubation period), cell loss was only 4 and 15% with poly(St/PEG-EEM/DMAPM) sized 78 and 200 nm, respectively. Poly(NIPAAm-co-MAH) cytotoxicity was insignificant. Poly(NIPAAm-co-MAH) uptake efficiency in SMCs was around 85%, but gene expression efficiency were low compared to poly(St/PEG-EEM/DMAPM)/pEGFP-N2 conjugates because of the low zeta potential of the co-polymer. Polymer uptake efficiencies of the nanoparticles were 90–95%. GFP expression efficiency was 68 and 64% after transfection with pEGFP-N2 conjugate with 78 and 200 nm sized poly(St/PEG-EEM/DMAPM) nanoparticles.

Preparation and lectin binding specificity of polystyrene particles grafted with glycopolymers bearing S-linked carbohydrates

Polystyrene particles bearing ATRP initiating groups, obtained by emulsifier-free emulsion polymerization of styrene (St) and 2-chloropropyloxyethyl methacrylate (CPEM), were subjected to surface-initiated activator generated by electron transfer for atom transfer radical polymerization (AGET ATRP) using glycomonomers, i.e., 4-vinylbenzenesulfonamidoethyl 1-thio-β- d-glucopyranoside ( 1) and 4-vinylbenzenesulfonamidoethyl 1-thio-β- d-lactoside ( 2). The glycopolymer-grafted polystyrene particles obtained Gp1 and Gp2 were shown to have hydrated graft layers of 15–65 nm in thickness on the cores of 370 nm in diameter. Gp1 and Gp2 coagulated in the presence of concanavalin A (Con A) and that of peanut agglutinin (PNA), respectively, showing highly specific response toward lectins.

Preparation of polymer core–shell particles supporting gold nanoparticles

The organic/inorganic composites were fabricated by catalytic reduction of tetrachloroaurate ions in poly[2-( N, N-dimethylamino)ethyl methacrylate] shell layers on polystyrene core particles. The core–shell particles were prepared by emulsifier-free emulsion polymerization of styrene (St) with 2-chloropropionyloxyethyl methacrylate (CPEM) using potassium persulfate as an initiator, followed by surface-initiated activator generated electron transfer-atom transfer radical polymerization (AGET-ATRP) of 2-( N, N-dimethylamino)ethyl methacrylate (DMAEMA) on core particles dispersed in aqueous media. The concentration effect of both DMAEMA ( x) and copper complex ( y) on a shell thickness of P(St-CPEM)- g-PDMAEMA x/ y core–shell particles was investigated by light scattering technique. The amount of grafted DMAEMA units with respect to (wrt) St was determined by 1H NMR spectra measurement. The P(St-CPEM)- g-PDMAEMA x/ y /Au z hybrid particles were successfully obtained by loading with hydrogen tetrachloroaurate (HAuCl 4) into the P(St-CPEM)- g-PDMAEMA aqueous dispersions. The particle size and shape of gold nanoparticles (NPs) generated by catalytic reduction in the poly[2-( N, N-dimethylamino)ethyl methacrylate] (PDMAEMA) shell layers were evaluated by both UV/vis absorption spectra measurement and TEM observation. The size and the number of gold NPs increased with increasing HAuCl 4 concentration ( z) below 75 mM. Interestingly, 60–80 nm sized, trigonal or polygonal, plate-like gold NPs were generated in the PDMAEMA shell by adding HAuCl 4 of 100 mM.

무효화 에멀젼 공중합법과 반응염법을 이용한 전기영동 고분자 컬러나노입자에 제조

무유화 에멀젼 공중합법을 이용하여 180-200 nm의 지름을 가지는 단분산성 폴리(스티렌/디비닐벤젠/비닐 아세테이틴) [poly(ST-co-DVB-co-VAc)] 고분자 나노입자를 합성하였으며. 제조된 단분산성 고분자 나노입자의 표면을 비누화반응을 통하여 개질하여 단분산성 폴리(스티렌/디비닐벤젠/비닐알코올) [polyl(ST-co-DVB-co-VA)] 나노입자를 제조하였다 합성된 입자를 반응염료와 반응시켜 적색과 청색 단분산성 폴리(스타렌/디비닐벤젠/비닐알코올 나노입자를 제조하였으며 입자의 형태, 분산성 빛 표면전하를 전자현미경, 시차열분석기, UV/Vis 흡광기 및 제타 전하 측정장치를 이용하여 규명하였다.

Preparation of glycopolymer hollow particles by sacrificial dissolution of colloidal templates

In this paper, a simple method for fabrication of glycopolymer hollow particles was demonstrated. The P(St-CPEM)- g-PVBSAELA core–shell particles were prepared by emulsifier-free emulsion polymerization of styrene (St) with 2-chloropropionyloxyethyl methacrylate (CPEM) using potassium persulfate as an initiator, followed by surface-initiated activator generated electron transfer–atom transfer radical polymerization (AGET–ATRP) of a styrene derivative bearing a lactose residue, i.e., N-2-4-(vinylbenzenesulfonamido)ethyl lactobionamide (VBSAELA). Dynamic light scattering measurement showed that the P(St-CPEM)- g-PVBSAELA core–shell particles possess graft layers of ca. 160 nm in thickness on the P(St-CPEM) core of 455 nm in diameter. By taking advantages of large difference in solubility between the PSt-based core and the PVBSAELA shell, the submicron-sized PVBSAELA hollow particles were obtained through a selective extraction of the core part from the P(St-CPEM)- g-PVBSAELA particles in tetrahydrofuran. The hydrodynamic diameter of the resulting hollow particles decreased by 15% compared to that of the corresponding core–shell particles. Finally, the micron-sized, raspberry-shaped, PVBSAELA hollow particles were successfully fabricated by a sacrificial dissolution of the PSt-based components from the PVBSAELA-grafted, core/shell heterocoagulates.

Preparation of organic/inorganic composites by deposition of silica onto shell layers of polystyrene (core)/poly[2-( N, N-dimethylamino)ethyl methacrylate] (shell) particles

Organic/inorganic composites were prepared by catalytic hydrolysis and subsequent condensation of tetraethoxysilane (TEOS) in a shell layer of core–shell polymer particles. First, core–shell particles were prepared by emulsifier-free emulsion polymerization of styrene (St) with 2-chloropropionyloxyethyl methacrylate (CPEM) using potassium persulfate as an initiator, followed by surface-initiated activator generated electron transfer–atom transfer radical polymerization (AGET–ATRP) of 2-( N, N-dimethylamino)ethyl methacrylate (DMAEMA). Dynamic light scattering revealed that hydrodynamic diameter of the particle increased from 482 to 931 nm after AGET–ATRP of DMAEMA. The amount of grafted DMAEMA was determined to be ca. 10 mol% with respect to (wrt) St by 1H NMR. Second, the composite particles were prepared by adding TEOS into a water/methanol dispersion of the P(St-CPEM)- g-P(DMAEMA). The P(St-CPEM)- g-P(DMAEMA)–SiO 2 composite particles containing ca. 50 wt.% of silica wrt the total weight were obtained. Hollow silica shell particles were also obtained by extraction of polymer components from the composites with tetrahydrofuran.

Monosize polycationic nanoparticles as non-viral vectors for gene transfer to HeLa cells

Monosized cationic nanoparticles were produced by emulsifier-free emulsion polymerization of styrene, poly(ethylene glycol) methacrylate and N-[3-(dimethyl-amino) propyl] methacrylamide, conducted in the presence of a cationic initiator, 2,2'-azobis (2-methylpropionamidine) dihydrochloride, using different amounts of ingredients and at different conditions. The structure of the terpolymers was confirmed by (1)H-NMR and FTIR spectroscopy. The nanoparticles, with an average size of 71.3 nm [polydispersity index (PDI), 1.110] and a Zeta potential of 65.6 mV obtained by a zeta sizer, were used in the transfection studies. HeLa cells were transfected in in vitro cell cultures with these non-viral nanoparticle vectors with a green fluorescent protein (GFP)-expressing plasmid DNA. The transfer of the cationic nanoparticles into the cells and GFP expressions with the conjugates of the nanoparticles and the GFP-expressing plasmid were followed by both light and fluorescent microscopy. The GFP expression efficiency was unexpectedly high (up to 90%).

PREPARATION OF POLYSTYRENE SEEDS AND PETAL-LIKE COMPOSITE POLYMER PARTICLES

The monodisperse submicron-size polystyrene(PSt) microspheres were prepared by emulsifier-free emulsion polymerization of styrene(St) using potassium persulfate(KPS) as initiator in ethanol-water mixed solvents.The effects of the concentration of KPS and St,polymerization temperature and the composition of the solvent on the size and morphology of PSt microspheres were investigated by scanning electron microscopy(SEM).The results indicate that the above factors evidently affect the diameter of the microspheres.The petal-like composite polymer particles were produced by emulsifier-free seeded emulsion polymerization in the presence of PSt seeds,styrene and acrylonitrile(AN) monomers using poly(ethylene glycol)(PEG) which has a methacryloyl group in the polymer end as reaction stabilizer.Such nonspherical shapes were controllable by change the ratio of St to AN.Such a surface morphology may provide a valuable information to elucidate the formation mechanism of the petal-like particles prepared by emulsifier-free seeded emulsion polymerization in the presence of PEG macromonomers.The result ulteriorly proved the formation mechanism of the unusual morphology for dispersion copolymerization system.

Synthesis and characterization of glycosylated nano particles

AbstractFunctionalized polymer nanoparticles have been synthesized by emulsifier-free emulsion polymerization of styrene with amino-functionalized monomers. Two monomers were used: the well-known 2- aminoethylmethacrylate and a new monomer with a styrenic polymerizable function, 4-(2-aminoethylthio)methylstyrene. The latexes were characterized by gravimetry, dynamic light scattering and colorimetric titration in order to obtain the styrene conversion, the hydrodynamic diameter, the particle size distribution and the concentration of surface amino groups, respectively. Then, glycosydic molecules such as maltose, lactose, maltotriose and galactopyranosylethanal were covalently grafted to the nanoparticles by amidation or reductive amination.

Double Roles of Stabilization and Destabilization of Initiator Potassium Persulfate in Surfactant-Free Emulsion Polymerization of Styrene under Microwave Irradiation

Emulsifier-free emulsion polymerization of styrene in a water/acetone mixture under microwave irradiation resulted in narrowly distributed stable polystyrene nanoparticles with an averaged hydrodynamic radius R(h) down to 35 nm when 50 wt % of acetone was added. For a given initiator potassium persulfate (KPS) concentration, R(h) was proportional to the monomer concentration in the range 1.2-7.0 wt %; while for a given monomer concentration, R(h) showed a minimum with an increasing initiator concentration. After both the roles of stabilization and destabilization of the initiator (KPS) were considered, we introduced a new parameter, the effective surface area stabilized per ionic group, and reformulated the Wu plot of R(h) proportional, variant W(monomer)/W(stabilizer) into R(h)/[k(1)(1 + k(2)W(KPS))] proportional, variant W(monomer)/W(initiator). It can qualitatively explain both the monomer and initiator concentration dependence of the particle size over a wide concentration range. The study of the salt effect showed that R(h) increased with the sodium sulfate concentration for fixed KPS and styrene concentrations.

Monodisperse thermosensitive particles prepared by emulsifier-free emulsion polymerization with microwave irradiation

The emulsifier-free emulsion polymerization of styrene (St) and N-isopropylacrylamide (NIPAAm) was successfully carried out with microwave irradiation, and the monodisperse thermoresponsive poly(styrene-co-N-isopropylacrylamide) (poly(St-co-NIPAAm)) particles with diameters in the range 100–130 nm were prepared. The morphology, size and size distribution of the poly(St-co-NIPAAm) particles were characterized by transmission electron microscopy, scanning electron microscopy (SEM) and photon correlation spectroscopy (PCS), respectively. The results showed that poly(St-co-NIPAAm) particles had spherical morphology, and the poly(St-co-NIPAAm) particles prepared by emulsifier-free emulsion polymerization with microwave irradiation were smaller, more uniform than those obtained with conventional heating. The hydrodynamic diameters of poly(St-co-NIPAAm) particles were decreased as the temperature increased from 25 °C to 40 °C, and poly(St-co-NIPAAm) particles collapsed remarkably at 32 °C, which is the lower critical solution temperature of the poly(N-isopropylacrylamide). The morphology of the assembled poly(St-co–NIPAAm) particles was observed by SEM, it was found that monodisperse poly(St-co-NIPAAm) particles could assemble to form the two-dimensional order structures.

Solvent-free photooxygenation of 5-methoxyoxazoles in polystyrene nanocontainers doped with tetrastyrylporphyrine and protoporphyrine-IX

A solvent-free route for the photooxygenation of the 5-methoxyoxazoles (1) is described. The substrates were embedded in nanosized polystyrene particles generated by the emulsifier-free emulsion polymerization of styrene with divinylbenzene and porphyrine dyes as cross-polymerizable reagents. From the photooxygenation of , the 1,2,4-dioxazoles (2) were formed and isolated from the reaction cavities by ethanol extraction. From comparison of the substrate conversions, the efficiency of singlet oxygen generation from the porphyrine dyestuff and the stability of the sensitizing material were estimated.