• Membrane Journal
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• v.18 no.2
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• pp.132-137
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• 2008

Nanofiltration membranes were prepared based on coating a sulfonated comb-like copolymer layer on top of a poly(vinylidene fluoride) (PVDF) support. The comb-like copolymer comprising poly(vinyl chloride) backbone and poly(styrene sulfonic acid) side chains, i.e. PVC-g-PSSA was synthesized by atom transfer radical polymerization (ATRP) using direct initiation of the secondary chlorines of PVC. The successful synthesis of graft copolymers were confirmed by nuclear magnetic resonance ($^1H$-NMR), FT-IR spectroscopy and wide angle X-ray scattering (WAXS). Composite nanofiltration membranes consisting PVC-g-PSSA as a top layer exhibited the increase of both rejections and solution flux with increasing PSSA concentration. This performance enhancement is presumably due to the increase of SO3H groups and membrane hydrophilicity. The rejections of composite membranes containing 71 wt% of PSSA were 88% for $Na_2SO_4$ and 33% for NaCl, and the solution flux were 26 and $34L/m^2h$, respectively, at 0.3 MPa pressure.

• Polymer(Korea)
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• v.34 no.6
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• pp.517-521
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• 2010

Microprous polyethylene (PE) membranes are widely used as lithium-ion battery separators. A separator having higher meltdown temperature than PE separator is still required for useful safety feature at a high temperature. To enhance meltdown temperature of PE separator, it was coated with polymers synthesized from bis-GMA derivatives by radical polymerization. Polymer was not formed when bis-GMA monomer having a high viscosity was used, while polymers were formed when bis-GMA derivatives having a low viscosity were used. When the separator was coated with polymer synthesized from reaction mixture containing proper amount of bis-GMA derivative, its meltdown temperature were increased up to $160^{\circ}C$ without reduction in the air permeability.

• Polymer(Korea)
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• v.31 no.6
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• pp.550-554
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• 2007

Atom transfer radical polymerization (ATRP) has been widely used in bioconjugation as it is an efficient and facile method to prepare polymers with pre-designed structures. Quite often, bioconjugation with proteins employs primary amines in proteins as a functional group to attach an initiator. When 2-bromoisobutryl bromide, the most widely used precursor for ATRP initiator, is used, ${\alpha}-halo$ amide initiating groups are formed in the proteins, which are known to exhibit slow initiation behavior in the ATRP process. Here we studied the ATRP of [poly(ethylene glycol)methyl ether] methacrylate (PEGMA) using amide-based initiator. PEGMA differs for both the nature and size of the polymer side branches and shows good solubility in water and a property that made it an ideal candidate for biomaterials. While normal ATRP produced ill-defined p(PEGMA) with amide based initiators, the halogen exchange method and the external additional of deactivator effectively improved the control of ATRP of PEGMA.

• Membrane Journal
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• v.19 no.2
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• pp.89-95
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• 2009

A comb-like copolymer consisting of a poly(vinyl chloride) backbone and poly(hydroxy ethyl acrylate) side chains, i.e. PVC-g-PHEA, was synthesized through atom transfer radical polymerization (ATRP). This comb-like copolymer was crosslinked with 4,5-imidazole dicarboxylic acid (IDA) via the esterification of the -OH groups of PHEA in the graft copolymer and the -COOH groups of IDA. Upon doping with phosphoric acid (PA, $H_3PO_4$) to form imidazole-PA complexes, the proton conductivity of the membranes continuously increased with increasing PA content. A maximum proton conductivity of 0.011 S/cm was achieved at $100^{\circ}C$ under anhydrous conditions. The PVC-g-PHEA/IDA/PA complex membranes exhibited good mechanical properties, i.e. 575 MPa of Young's modulus, as determined by a universal testing machine (UTM). Thermal gravimetric analysis (TGA) shows that the membranes were thermally stable up to $200^{\circ}C$.

• Elastomers and Composites
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• v.48 no.1
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• pp.30-38
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• 2013

Polyolefin is one of the most important commodity polymers having excellent physical properties and cost competitiveness, which has continuously broadened their market in response to a heavy demand from industry. However, the lack of polarity in polyolefin has limited its applications, especially where interactions with other materials are important. In view of the above, the incorporation of polar functional groups in polyolefin has been widely attempted. Especially, the preparations of segmented modified polyolefin copolymers, such as block and graft copolymers have been extensively investigated, since the loss of the original properties of polyolefin can be minimized while the polar segments can endow interactions with other materials. Living radical polymerization (LRP) method can be one of the most attractive synthetic tools for the preparation of the modified polyolefin block or graft copolymers. In this review, progress on the preparation of the polyolefin based block or graft copolymers through LRP technique is briefly summarized.

• Membrane Journal
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• v.21 no.1
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• pp.39-45
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• 2011

An amphiphilic graft copolymer consisting of a poly(vinyl chloride) (PVC) backbone and poly(styrene sulfonic acid) (PSSA) side chains (PVC-g-PSSA) was synthesized via atom transfer radical polymerization (ATRP). This polymer electrolyte membrane was ion-exchanged to Ag ions by immersing in 10 wt% $AgNO_3$ aqueous solution and templated the growth of Ag nanoparticles by a reducing agent. The formation of Ag nanoparticles was confirmed using UV-visible spectroscopy and X-ray diffraction (XRD). Transmission electron microscopy (TEM) revealed that utilization of $NaBH_4$ was the most effective in the formation of Ag nanoparticles with 10~15 nm in size. The formation of Ag nanoparticles was also strongly affected by the concentration of reducing agent and reduction time.

• Polymer(Korea)
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• v.35 no.6
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• pp.615-618
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• 2011

Carbon nanotubes (CNTs) draw attention as promising materials due to their excellent electrical and mechanical properties. However, the intrinsic strong interaction between CNTs presents a challenge to their use in various applications. Here, we present a facile method to disperse single-walled carbon nanotubes (SWCNTs) in a polar solution using a graft copolymer, poly(vinyl chloride)-graft-poly(oxyethylene methacrylate), PVC-g-POEM. The graft copolymer was synthesized via atom transfer radical polymerization (ATRP), as confirmed by gel permeation chromatography (GPC) and $^1H$ NMR spectroscopy. The SWCNTs were uniformly dispersed in a polar solvent such as dimethylsiloxane (DMSO) using PVC-g-POEM as a dispersant, due to interaction between CNT and the graft copolymer, as revealed by transmission electron microscopy (TEM) analysis. Upon removal of the solvent, free standing nanocomposite films with good homogeneity were obtained.

• Polymer(Korea)
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• v.38 no.1
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• pp.16-23
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• 2014

A novel poly(AM-DMDAAC)/MMT superabsorbent nanocomposites are prepared by radical polymerization using ammonium persulfate (APS) and anhydrous sodium sulfite as a free radical initiator and N,N-methylene bisacrylamide (MBA) as a crosslinker. In this paper, an optimization study on the synthesis of superabsorbent nanocomposites is carried out. Orthogonal array experiment indicates that the optimized conditions is acrylamide (AM) content 23 wt%, diallyl dimethyl ammonium chloride (DMDAAAC) content 6 wt%, montmorillonite (MMT) content 4 wt%, initiator content 0.2 wt% and crosslinker content 0.02 wt%. Under the optimization syntheses conditions concluded, the maximum water absorbency in distilled water is $659.53g{\cdot}g^{-1}$ and in 2 wt% sodium chloride solution is $116.25g{\cdot}g^{-1}$. Compared with the range values of different factors ($R_j$), the order of significance factors in distilled water is C (MMT) > B (DMDAAC) > A (AM) > D (crosslinker) > E (initiator). MMT is intercalated during polymerization reaction and a nanocomposite structure is formed as shown by TEM analysis and XRD analysis.

• Applied Chemistry for Engineering
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• v.29 no.3
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• pp.330-335
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• 2018

A new approach for the fabrication of organic-organic conducting composite thin films using simultaneous co-vaporization vapor phase polymerization (SC-VPP) of two or more monomers that have different polymerization mechanisms (i.e., oxidation-coupling polymerization and radical polymerization) was reported for the first time. In this study, a PEDOT-PSMA composite thin film consisting of poly(3,4-ethylenedioxythiophene)(PEDOT) and poly(styrene-co-maleic anhydride)(PSMA) was prepared by SC-VPP process. The preparation of organic-organic conductive composite thin films was confirmed through FT-IR and $^1H-NMR$ analyses. The surface morphology analysis showed that the surface of PEDOT-PSMA thin film was rougher than that of PEDOT thin film. Therefore, PEDOT-PSMA exhibited lower electrical conductivity than that of PEDOT. But the conductivity can be improved by adding 2-ethyl-4-methyl imidazole as a weak base. The contact angle of PEDOT-PSMA was about $50^{\circ}$, as compared to $62^{\circ}$ for PEDOT. The demonstrated methodology for preparing an organic-organic conductive hybrid thin film is expected to be useful for adjusting intrinsic conductive polymer (ICP)'s surface properties such as mechanical, optical, and roughness properties.

• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2694-2698
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• 2014

A multisegmented polystyrene (PS) with pH-cleavable ester and carbamate linkages was successfully synthesized by a combination of atom transfer radical polymerization (ATRP) and Cu(I)-catalyzed 1,3-dipolar cycloaddition of azide and alkynes (click chemistry). ATRP was employed to synthesize polystyrene from hydroxyl-terminated initiator using CuBr/N,N,N',N",N"-pentamethyldiethylenetriamine (PMDETA) as the catalyst. The reaction of the resulting PS with sodium azide yielded the azido-terminated polymer. The hydroxyl group in the other end of the polymer was reacted with 4-nitrophenyl chloroformate (NPC), followed by reaction with propargylamine to produce an alkyne end group with a carbamate linkage. The PS with an alkyne group in one end and an azide group in the other end was then self-coupled in the presence of CuBr/2,2'-bipyridyl (bpy) in DMF to yield a desired multisegmented PS. Molecular weight and molecular weight distribution of the self-coupled polymer increased with time, as in the typical step-growth-type polymerization processes. Finally, we demonstrated that the ester and carbamate linkages of the multisegmented PS were hydrolyzed in the presence of HCl to yield individual PS chains.