• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.322-322
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• 2006

Well-defined poly(N-vinylcarbazole), poly(NVC), was synthesized by macromolecular design via interchange of the xanthate (MADIX)/reversible addition-fragmentation chain transfer (RAFT) polymerization in the presence of a suitable xanthate-type chain transfer agent (CTA). Good control of the polymerization was confirmed by the linear first-order kinetic plot, the molecular weight controlled by the monomer/CTA molar ratio, linear increase in the molecular weight with the conversion, and the ability to extend the chains by the second addition of the monomer. Star polymers having various architectures were also synthesized using this technique.

• Macromolecular Research
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• v.10 no.1
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• pp.18-23
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• 2002

We theoretically consider blends of two monodisperse one-end-functionalized homopolymers (denoted by A and B) capable of forming clusters between functional groups (stickers) using weak segregation theory. In this model system resulting molecular architectures via clustering resemble star copolymers having many A- and B-arms. Minimizing the total free energy with respect the cluster distribution, the equilibrium distribution of clusters is obtained and used for RPA (Random Phase Approximation) equations as input. For the case that polymers are functionalized by only one kind of sticker, the phase diagrams show that the associations promote the macrophase separation. When there is strong affinity between stickers belonging to the different polymer species, on the other hand, the phase diagram show a suppression of the macrophase separation at the range of high temperature regime, as well as the phase coexistence between a disordered and a mesoscopic phase at the relatively lower temperatures.

• Polymer(Korea)
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• v.27 no.3
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• pp.255-264
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• 2003

Various chain sizes 3-arm star polystyrenes (PS, $M_{w}$=2.80$\times$10$^{5}$ , 2.49$\times$10$^{6}$ g/mol) in t-decalin solution were measured at the temperature range of 20~7$0^{\circ}C$ by means of viscometry and laser light scattering. In order to show universality in the expansion factor of 3-arm star polymer, it was expected that (N/ $R_{G,Br,o}$$^{2}$)$^{3}$2/$\tau$/$\tau$$_{C}$ would be used as an universal parameter, where $R_{G,Br,o}$ was the unperturbed radius of gyration of star PS. However, much better universality had been observed when (N/ $R_{G,Br,o}$$^{2}$)$^{3}$2/$\tau$/$\tau$$_{C}$ parameter of the linear PS was used even for the 3-arm star PS. It could be explained if branching effect had been already taken into account in the part of $\tau$/$\tau$$_{C}$(=[(Τ-Θ$_{Tc}$ )/Θ$_{Tc}$ ]/[(Θ$_{Tc}$ -Τ$_{c}$)/ $T_{c}$]). Here N and Θ$_{Tc}$ stand for the number of monomer unit in a single polymer chain and a kind of theta temperature as the critical solution temperature $T_{c}$ of the infinite molecular weight, respectively.ely.y.ely.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.05a
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• pp.59-62
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• 1993

This Paper studies on thermal oxidation of alumina filled epoxy network polymer used in Extra-High voltage application. The thermal oxidation of surface has investigated by yellow index variation and various electrical properties which are surface resistivity, tracking resistance and AC dielectric strength are estimated by yellow index.

• Membrane Journal
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• v.29 no.5
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• pp.252-262
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• 2019

A sulfonated star branched poly(styrene-b-butadiene-b-styrene) triblock copolymer (SSBS) was synthesized with varying degrees of sulfonation. The effective sulfonation on the butadiene block was confirmed by FT-IR spectroscopy. Ion exchange capacity by titration was used to determine the degree of sulfonation. The synthesized polymer observed enhanced water uptake and proton conductivity. At room temperature, the SSBS with 25 mol% degree of sulfonation showed an outstanding proton conductivity of 0.114 S/cm, similar to that of commercial membrane, Nafion. The effect of temperature at constant relative humidity on conductivity resulted to a remarkable increase in proton conductivity. Methanol permeability studies showed a value lower than Nafion for all the sulfonated membranes. Structural nature observed using AFM showed that the membranes observed microphase separated nanostructures and the connectivity of the interionic channels.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.1-2
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• 2006

Polymer architecture plays a great role in determining the properties of functional polymers. This lecture will explore the design and the synthesis of polymers with controlled architecture and functionality. Especially featured will be star and dendritic architectures where the functional group placement and the molecular shape can be controlled. This will be followed by examples of applications illustrated with a few model systems of functional polymers designed for use in areas such as organic electronics, catalysis, surface patterning, separation and molecular recognition, and polymer therapeutics.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.93-94
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• 2006

This lecture will present an overview of recent advances in our transition metal-mediated living radical polymerization, particularly focused on catalyst design and precision synthesis of functional polymers. Selected topics will include: (A) Design of Transition Metal Complexes: Evolution of Catalysts (B) New Ruthenium and Iron Catalysts: Active and Versatile (C) Functional Methacrylates for Advanced Functional Polymers (D) Functional Star Polymers: Microgel Cores for Metal Catalysts.

• Proceedings of the Korean Fiber Society Conference
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• 1992.06a
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• pp.44-44
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• 1992

• Advances in aircraft and spacecraft science
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• v.3 no.4
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• pp.427-445
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• 2016

Star sensors are the attitude estimation sensors of the satellite orbiting in its path. It gives information to the control station on the earth about where the satellite is heading towards. It captures the images of a predetermined reference star. By comparing this image with that of the one captured from the earth, exact position of the satellite is determined. In the process of imaging, stray lights are eliminated from reaching the optic lens by the mechanical enclosures of the star sensors called Baffles. Research in space domain in the last few years is mainly focused on increased payload capacity and reduction in launch cost. In this paper, a star sensor baffle made of Aluminium is considered for the study. In order to minimize the component weight, material wastage and to improve the structural performance, an alternate material to Aluminium is investigated. Carbon Fiber Reinforced Polymer is found to be a better substitute in this regard. Design optimisation studies are carried out by adopting suitable design modifications like implementing an additional L-shaped flange, Upward flange projections, downward flange projections etc. A better configuration of the baffle, satisfying the design requirements and achieving manufacturing feasibility is attained. Geometrical modeling of the baffle is done by using UNIGRAPHICS-Nx7.5(R). Structural behavior of the baffle is analysed by FE analysis such as normal mode analysis, linear static analysis, and linear buckling analysis using MSC/PATRAN(R), MSC-NASTRAN(R) as the solver to validate the stiffness, strength and stability requirements respectively. Effect of the layup sequence and the fiber orientation angle of the composite layup on the stiffness are also studied.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.301-301
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• 2006

The physical properties of well-defined star-shape polystyrenes with high number of arms (6 to 57 arms) in good and theta solvents were studied using synchrotron X-ray scattering. The scattering profiles for multi-armed polystyrenes shown the molecular shape is changed according to increasing of number of arm. From various parameters which were obtained from scattering profiles, the molecular shape was determined more detail. As results, the molecular shape was changed from a fuzzy-ellipsoid for 6-armed PS to a fuzzy-sphere sphere for 57-armed PS according to increasing of number of arm.