• Elastomers and Composites
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• v.31 no.3
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• pp.175-182
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• 1996

Polymer latices, prepared from the emulsion polymerization of vinyl monomer compounds, are widely used for many industrial applications. Included among these are uses in paints, adhesives, flocculants, and heavy-duty plastics as well as their original use in synthetic rubber compounds. The emulsion polymerization process with chemical initiator has chemical disadvantage such as removal of initiator which was left after polymerization. In this study, polystyrene latex was prepared by using ultrasonic irradiation which generate the free radical, and then it was analyzed by GPC. Reaction temperature hardly have an effect on average molecular weight. Average molecular weight is increased by increasing amount of surfactant, i.e. SDS, but polydispersity is decreased. After 90 minutes of reaction time, increase and decrease of average molecular weight Is repeated. It is proposed that monodisperse polymer is obtained by controlling ultrasonic irradiation time and surfactant concentration.

• Polymer(Korea)
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• v.36 no.2
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• pp.177-181
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• 2012

This study presents the preparation of double emulsions in a poly(dimethylsiloxane) (PDMS)-based microfluidic device. To improve the wettability of hydrophilic continuous phase onto a hydrophobic PDMS microchannel, the surface was modified with 3-(trimethoxysilyl) propyl methacrylate (TPM) and then sequentially reacted with acrylic acid monomer solution, which produced selective covalent bonding between acrylic acids and methacrylate groups. For the proof of selective surface modification, tolonium chloride solution was used to identify the modified region and we confirmed that the approach was successfully performed. When water containing 0.5% w/w sodium dodecyl sulfate and 1% w/w Span80 with hexadecane were loaded into the selectively modified microfluidic channels, we can produce stable double emulsion. Based on the spreading coefficients, we predict the morphology of double emulsions. Our proposed method efficiently produces monodisperse double emulsions having 48.5 ${\mu}m$(CV:1.6%) core and 65.1 ${\mu}m$ (CV:1.6%) shell. Furthermore, the multiple emulsions having different numbers of core were easily prepared by simple control of flow rates.

• Korean Journal of Materials Research
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• v.22 no.8
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• pp.433-438
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• 2012

A chemical process involves polymerization within microspheres, whereas a physical process involves the dispersion of polymer in a nonsolvent. Nano-sized monodisperse microspheres are usually prepared by chemical processes such as water-based emulsions, seed suspension polymerization, nonaqueous dispersion polymerization, and precipitation polymerizations. Polymerization was performed in a four-necked, separate-type flask equipped with a stirrer, a condenser, a nitrogen inlet, and a rubber stopper for adding the initiator with a syringe. Nitrogen was bubbled through the mixture of reagents for 1 hr. before elevating the temperature. Functional silane (3-mercaptopropyl)trimethoxysilane (MPTMS) was used for the modification of silica nanoparticles and the self-assembled monolayers obtained were characterized by X-ray photoelectron spectroscopy (XPS), laser scattering system (LSS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), elemental analysis (EA), and thermogravimetric analysis (TGA). In addition, polymer microspheres were polymerized by radical polymerization of ${\gamma}$-mercaptopropyl modified silica nanoparticles (MPSN) and acrylamide monomer via precipitation polymerization; then, their characteristics were investigated. From the elemental analysis results, it can be concluded that the conversion rate of acrylamide monomer was 93% and that polyacrylamide grafted to MPSN nanospheres via the radical precipitation polymerization with AAm in ethanol solvent. The microspheres were successfully polymerized by the 'graft from' method.

• Journal of Adhesion and Interface
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• v.15 no.3
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• pp.93-99
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• 2014

Monodisperse poly[styrene-co-(COPS-I)] latices in the size range of 165~550nm were successfully prepared by soap-free emulsion polymerization with various polymerization conditions (Styrene, COPS-I, KPS, DVB concentrations and polymerization temperature). In general, the COPS-I and KPS, DVB concentrations and polymerization temperature were closely related to the polymerization rate and the number of particles, molecular weight, and zeta potential. The polymerization rate and zeta potential increased, but molecular weight decreased, with increasing in the number of particles.

• Polymer(Korea)
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• v.28 no.6
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• pp.524-530
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• 2004

Polystyrene particles (PS) with poly(ethylene glycol) units on surface were formed by an emulsifier-free emulsion polymerization using styrene, poly(ethylene glycol) methacrylate (PEG-MMA) or poly(ethylene glycol) dimethacrylate (PEG-diMMA) at pH 7, and followed by freeze-drying to give the corresponding powders. The structures of PS particles were confirmed by FT-IR spectroscopy, and the particle size and distribution the PS particle were observed by scanning electron microscopy and particle analyzer. Monodisperse polymer particles were obtained at a concentration of PEG-MMA 2∼5 mol% or PEG-diMMA 1 mol% relative to styrene. The highest zeta potential of polymer surface was measured to be 183 mV at a polymer of PEG-MMA 5 mol%, which was measured in dielectric medium by means of ELS-8000 dynamic light scattering.

• Polymer(Korea)
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• v.29 no.5
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• pp.445-450
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• 2005

Hyaluronic acid-based beads were prepared in order to develop a biomedical material for augumentation. Hyaluronic acid was crosslinked by 1,3-butadiene diepoxide in a suspension state maintained by rapid mixing of soybeen oil and hyaluronic acid solution. The particle size, surface area and swelling ratio were measured to investigate the physical properties of the synthesized beads and the bead surface was examined by scanning electron microscopy. The beads were formed in the range of $5-12vol\%$ concentration of crosslinking agent, which showed monodisperse size distribution. Both BET surface area and swelling ratio decreased as the concentration of either hyaluronic acid or crosslinking agent increased, and crosslinking temperature decreased. Bead size could be effectively controlled by mixing speed without affecting other physical property.

• Polymer(Korea)
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• v.27 no.4
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• pp.370-376
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• 2003

Poly(DL-lactide-co-glycolide) nanoparticles were prepared by the modified spontaneous emulsification solvent diffusion method. Polymer solution was prepared by two water-soluble organic solvents, such as ethanol and acetone. Because of its biocompatible nature, PEG-PPG diblock copolymer was used as surfactant and stabilizer. The influence of several preparative variables on the nanoparticle formation, such as type and concentration of stabilizing agent, stirring methods, water/oil phase ratio and polymer concentration were investigated in order to control and optimize the process. After preparation of nanoparticles, particle size and distribution were evaluated by the light scattering particle analyzer. As results, the particle size was 50-200 nm and dispersibility was monodisperse. It was found that the appropriate selections of binary solvent mixtures and polymeric concentrations in both organic and aqueous phases could provide a good yield and favorable physical properties of PLGA nanoparticles.

• Macromolecular Research
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• v.11 no.6
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• pp.437-443
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• 2003

A series of alternating and alternating block copolycarbonates containing the constituent groups of polysulfone was synthesized through a multi-step solution condensation method. For the regulation of block length, monodisperse oligomers were prepared by using a large excess of the bisphenols and were subsequently incorporated into the copolymer chains. Separating the unreacted bisphenols from the oligomers by dissolution/precipitation steps took advantage of solubility differences. The structures of the monomers, oligomers, and copolymers were characterized and confirmed by GPC, NMR spectroscopy, mass spectrometry, and elemental analysis. Monodispersity of the oligomers, which is critical for control over the block length in the copolymers, was confirmed by GPC and mass spectrometry. Of the two constituent groups of the polysulfone, the sulfone linkage stiffens the polycarbonate copolymer chain, while the ether linkage softens it.

• Macromolecular Research
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• v.9 no.2
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• pp.122-128
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• 2001

Monodisperse composite latex particles with size of ca. 300 nm, which consist ofn-butyl acrylate as a soft phase and methyl methacrylate as a hard phase with different morphology, were synthesized by seeded multi-stage emulsion polymerization. Three types of composite latex particles including random-, core/shell-, and gradient-type particles were obtained by using different monomer feeding methods during semi-batch emulsion polymerization. Effect of poly(butyl acrylate)-poly(methyl methacrylate) rubber particle morphology on the mechanical and rheological properties of rubber toughened poly(methyl methacrylate) was investigated. Among three different rubber particles, the gradient-type rubber particle showed better toughening effect than others. No significant variation of rheological property of poly(methyl methacrylate)/rubber blends was observed for the different rubber particle morphology.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1021-1024
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• 2003

In this work, we fabricated various 2D metallic and polymeric nanopatterns with the feature resolution of sub-micrometer scale by using the method of microcontact printing ($\mu$ P) based on soft lithography. Silicon masters for the micromolding were made by e-beam lithography. Composite poly(dimethylsiloxane) (PDMS) molds were composed of a thin, hard layer supported by soft PDMS layer. Finally, monodisperse metal or polymer particles could be obtained in the prepared pattern for the application of electronic devices.