• Bulletin of the Korean Chemical Society
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• v.18 no.1
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• pp.38-43
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• 1997

Poly(ethylene 2, 6-naphthalate-co-tetramethylene 2, 6-naphthalate) (PEN/PBN) copolymers were synthesized and studied by 13C NMR spectroscopy, DSC analysis and X-ray diffraction. A minimum in the melting point vs. composition curve was found at approximately 60 mol% tetramethylene 2, 6-naphthalate. The PEN/PBN copolymers were shown to be statistically random throughout the range of 1, 4-butanediol compositions. The melting point depression behavior of annealed PEN/PBN copolymers depended upon the sequence propagation probability, PS, which is suggested by indivisual crystal formation of two pure comonomers; that is, ethylene-naphthalate-ethylene, EE, and tetramethylene-naphthalate-tetramethylene, BB. However, it can be seen from the X-ray curve that the peaks of PEN/PBN copolymers appear from a crystal lattice which is governed only by the rich component between two different aliphatic units in the copolymer composition.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.42-47
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• 2018

This work reports a facile and effective antibacterial coating for oxide substrates. As a coating material, a random copolymer, abbreviated as poly(TMSMA-r-PEGMA), was synthesized by radical polymerization of 3-(trimethoxysilyl)propyl methacrylate (TMSMA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA). Polymeric self-assembled monolayers of poly(TMSMA-r-PEGMA) were formed on various inorganic oxide substrates, including silicon oxide, titanium dioxide, aluminum oxide, and glass, via the simple dip-coating process. The polymer-coated substrates were characterized by ellipsometry, contact angle measurements, and X-ray photoelectron spectroscopy. The bacterial adhesion on the polymer-coated substrates was completely suppressed compared to that on the uncoated substrates.

• Polymer(Korea)
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• v.24 no.5
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• pp.638-645
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• 2000

Linear and star-shaped, poly(lactic acid) (PLA) stereo-block copolymers were synthesized by sequential polymerization of DL-lactic acid and L-lactide in the presence of diol or polyol compounds. The molecular weight of block copolymers could be controlled to some extent by the variation of alcohol content. These block copolymers had relatively narrow molecular weight distributions. The glass transition temperature and melting temperature of block copolymers appeared at around 5$0^{\circ}C$ and 100~14$0^{\circ}C$, respectively. The block copolymers were found to crystallize even at the high D-stereoisomer concentration of 35 mol%, in contrast to the amorphous nature of the random copolymer with similar composition. Also we could observe the crystallinity of PLA stereo-block copolymers varying with annealing temperature and time.

• Fibers and Polymers
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• v.3 no.1
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• pp.18-23
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• 2002

The structure development and dynamic properties of fibers produced by high-speed spinning of P(EN-ET) random copolymers were investigated. The as-spun fibers were found to remain amorphous up to the spinning speed of 1500 m/min, and subsequent increases in speed resulted in the crystalline domains containing primarily $\alpha$ crystalline modification of PEN. The f modification was not found up to spinning speeds of 4500 m/min. On the other hand, annealing of constrained fibers spun at the 2100 m/min at 180,200, and 240^{\circ}C$ exhibited $\beta$-form crystalline structure, while the annealed fibers spun in 600-1500 m/min range exhibited dominantly $\alpha$-form. However $\beta$-form crystals disappeared above the spinning speed of 3000 m/min. With increasing spinning speeds from 600 to 4500 m/min, the storage modulus of as-spun fibers increased continuously and reached a value of about 10.4 spa at room temperature. The tan $\delta$curves showed the $\alpha$-relaxation peak at about 155-165^{\circ}C$, which is considered to correspond to the glass transition. The $\alpha$-relaxation peaks became smaller and broader, and shift to higher temperatures as the spinning speed increases, meaning that molecular mobility in the amorphous region is restricted by increased crystalline domain.

• Journal of the Korean Applied Science and Technology
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• v.21 no.2
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• pp.132-139
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• 2004

Film forming behavior of monodispersed model composite latexes with particle size of 190 nm, which consist of n-butyl acrylate as a soft phase monomer and methyl methacrylate as a hard phase monomer with different morphology was examined. Five different types of model latexes were used in this study such as random copolymer particle, soft-core/hard-shell particle, hard-core/soft-shell particle, gradient type particle, and mixed type particle. The film forming behavior was evaluated using pseudo on-line measurements of the cumulative weight loss, the UV transmittance, and the tensile fracture energy. Each stages of film formation I, II were not sensitive to the morphology of model latexes, but stage-ill was largely dependent on the morphology of model latexes. The chain mobility of polymer which composed the shell component was found to dominantly determine the behavior of film forming stage-III.

• Macromolecular Research
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• v.11 no.2
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• pp.80-86
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• 2003

The polymerization of a cyclopolymerizable disubstituted dipropargyl ether, his(3-trimethylsilyl-2-propynyl)ether (BTPE), was attempted by various transition metal catalysts. The yield for the polymerization of BTPE was generally low, which is possibly due to the steric hindrance of bulky substituents. In general, the catalytic activities of Mo-based catalysts were found to be greater than those of W-based catalysts. The highest yield was obtained when the MoCl$_{5}$,-EtAlCl$_2$(1:2) catalyst system was used. The copolymerization of BTPE and diethyl dipropargylmalonate yielded a random copolymer with conjugated polymer backbone. However the polymers were partially desilylated, depending on the reaction conditions. The thermal and morphological properties of the resulting polymers were also discussed.d.

• Composites Research
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• v.35 no.3
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• pp.127-133
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• 2022

Polypropylene (PP) has been received great attention as a next-generation high-voltage power cable insulation material that can replace cross-linked polyethylene (XLPE). However, the PP cannot be used alone as an insulation material because of its high elastic modulus and vulnerability to impact, and thus is mainly utilized as a form of a copolymer with rubber phases included in the polymerization step. In this paper, a soft PP-based blend was prepared through melt-mixing of impact PP, polyolefin elastomer, and propylene-ethylene random copolymer. The elastic modulus and impact strength of the blend could properly be decreased or increased, respectively, by introducing elastomeric phases. Furthermore, the blends showed a high storage modulus even at a temperature of 100℃ or higher at which the XLPE loses its mechanical properties. In addition, the blend was found to be effective in suppressing the space charge compared to the pristine PP as well as XLPE.

• Journal of the Korean Chemical Society
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• v.40 no.1
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• pp.11-19
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• 1996

The cationic polymerization of energetic substituted oxetanes which have pendant energetic group such as azido and nitrato are investigated theoretically, using semiempirical HF/3-21G, MINDO/3, MNDO and AM1 method. The stereo- and electronic structure of binary molecular complex composed of energetic substituted oxetane and boron trifluoride can be explain by molecular orbital theory. The reactivity of propagation in the copolymerization of oxetanes can be presented by the positive charge on carbon(C2) atom of oxetane and energy level of the lowest unoccupied molecular orbital(LUMO) of propagating species of oxetanes. The reactivity ratios for copolymerization of oxetanes are a random copolymer-zation which is agree with MO calculated and experimental results. The relative equlibrium concentration of cyclic oxonium and open carbenium ions is found to be a major determinant of mechanism, owing to the rapid equilibrium of these cation forms and the expectation based on calculation that in the prepolymer propagation step, SN1 mechanism will be at least as fast as that for SN2 mechanism.

• Korea-Australia Rheology Journal
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• v.21 no.4
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• pp.203-211
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• 2009

In flows with deformation rates larger than the inverse Rouse time of the polymer chain, chains are stretched and their confining tubes become increasingly anisotropic. The pressures exerted by a polymer chain on the walls of an anisotropic confinement are anisotropic and limit chain stretch. In the Molecular Stress Function (MSF) model, chain stretch is balanced by an interchain pressure term, which is inverse proportional to the $3^{rd}$ power of the tube diameter and is characterized by a tube diameter relaxation time. We show that the tube diameter relaxation time is equal to 3 times the Rouse time in the limit of small chain stretch. At larger deformations, we argue that chain stretch is balanced by two restoring tensions with weights of 1/3 in the longitudinal direction of the tube (due to a linear spring force) and 2/3 in the lateral direction (due to the nonlinear interchain pressure), both of which are characterized by the Rouse time. This approach is shown to be in quantitative agreement with transient and steady-state elongational viscosity data of two monodisperse polystyrene melts without using any nonlinear parameter, i.e. solely based on the linear-viscoelastic characterization of the melts. The same approach is extended to model experimental data of four styrene-butadiene random copolymer melts in shear flow. Thus for monodisperse linear polymer melts, for the first time a constitutive equation is presented which allows quantitative modeling of nonlinear extension and shear rheology on the basis of linear-viscoelastic data alone.

• Polymer(Korea)
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• v.24 no.1
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• pp.58-64
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• 2000

Poly(butylene terephthalate-co-oxybenzoate) (PBOT ) was synthesized by melt trans-esterification of poly(butylene terephthalate)(PBT) and p-acetoxybensoic acid (ABA) at 250, 260, and 27$0^{\circ}C$ with the compositions of PBT/ABA of 4/6, 5/5, 6/4. The sequence analysis of PBOT with a $^1$H FT-NMR indicated that the number of consecutive oxybenzoate units ranges from 1.2 to 1.5, which is larger than that of the corresponding poly(ethylene terephthalate)(PET)/ABA (PEOT) obtained at the same reaction conditions as the PBOT. The difference in the block length influenced the thermal degradation behavior: Polyoxybezoate (POB), PBT and PEOT showed one-step degradation whereas PBOT exhibited two-step degradation. The results suggested that PBOT consisted of three phases of PBT-rich phase, random phase of PBT and ABA, and ABA-rich phase.