• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.1
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• pp.59-64
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• 2004

We have fabricated the polymer dispersed liquid crystal (PDLC) cell where a control of phase separation is very important. The factors to influence the phase separation are mixing ratio of LC and polymer, curing temperature and UV intensity. In this paper, we inspected the change of a phase separation as a function of curing temperature for the mixture of E7 and. NOA65 with different ratios. When the LC concentration is less than polymer such as LC:NOA65 = 40:60wt％, the PDLC cell is influenced strongly by the curing temperature. However, when the LC concentration is much less than polymer such as LC:NOA65 = 80:20wt％, it is influenced slightly by the curing temperature. The reason is because the mixture shows upper critical solution temperature behavior and therefore it is important to know the behavior of phase separation as a function of curing temperature of the mixture.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.501-504
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• 2014

A thermoresponsive polymer, poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA), was successfully synthesized by atom transfer radical polymerization (ATRP). Different amounts of 1,3-propanesultone were used as quaternization agent to transit the PDMAEMA into partially modified poly(zwitterions), resulting in p[DMAEMA-co-3-dimethyl(methacryloyloxyethyl)ammonium propanesulfonate] (PDMAEMA-co-PDMAPS). Molecular weight, molecular weight distribution, and degree of quarternization were determined by gel permeation chromatography (GPC) and 1H NMR spectroscopy. The transmission spectra of the 1.0 wt % aqueous solutions of the resulting polymers at 650 nm were measured as a function of temperature. Results showed that the lower critical solution temperature (LCST) and the upper critical solution temperature (UCST) could be easily controlled by the different composition of dimethylamino and zwitterion groups. The effect of partial quaternization on thermoresponsive properties was also studied by dynamic light scattering (DLS) with the same aqueous concentration (1.0 wt %) as employed for turbidimetry studies. The LCST and UCST values measured by DLS correlated well with those determined by turbidimetry.

• Journal of the Korean Chemical Society
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• v.58 no.6
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• pp.528-534
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• 2014

In some binary solution, closed miscibility loop of temperature-composition phase diagram occurs where both an upper critical solution temperature and a lower critical solution temperature exist. It is known that this phenomena occurs if specific interaction between molecules exists. There are several ways describing the specific interaction. In this work it is assumed that the total number of specific interactions is distributed according to binomial distribution. In this case, exact mathematical conditions for closed miscibility loop phase behavior are derived when the specific interaction is applied to regular solution theory, quasichemical theory and Flory-Huggins lattice theory. And we investigated the effect of parameters on the phase diagram. The phase diagram of water-nicotine is calculated and compared with experimental data.

• Polymer(Korea)
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• v.38 no.4
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• pp.530-534
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• 2014

Polyethylene (PE) membranes having various porosities are used as microfilters and separators in lithium ion batteries. Membranes having a high porosity are required for use as separators in a large scale lithium ion secondary battery. In this study, BET was examined for use as a new nontoxic diluent for the fabrication of highly porous PE membranes by thermally induced phase separation process. It was confirmed that BET can be used as a new diluent for the fabrication of the PE membranes by exploring upper critical solution temperature type phase behavior of PE mixtures with BET. When the porosity of the membrane prepared from the PE/PO mixture was compared with that prepared from PE/BET mixture, the latter was about 1.8 times higher than the former.

• Macromolecular Research
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• v.10 no.6
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• pp.359-364
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• 2002

A series of PLA-PEO-PLA triblock stereo-copolymers with varying PLA/PEO and L-DL-LA ratios were synthesized via ring opening pelymerizations. Aqueous solutions of these copolymers undergo thermo-responsive phase transitions as the temperature monotonically increases. Further study shows that there is a critical gel concentration (CGC), and also lower and upper critical gel temperatures (CGTs), at which the thermo-responsive phase transition occurs. The CGC and CGTs are affected by various factors such as block length, as well as the compositions of the PLA blocks and of the additives. In particular, the changes in the phase diagram produced by varying the L-/DL-LA ratio in the PLA blocks were determined to be mainly due to consequent stereo-regularity changes in the PLA blocks.

• Clean Technology
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• v.13 no.1 s.36
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• pp.28-33
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• 2007

We measured cloud points of Poly(methylmethacrylate) (PMMA) in various solvents using the high-pressure variable volume view cell apparatus. The solvents used for dissolving PMMA were chlorodifluoromethane (HCFC-22), dimethylether (DME), 1,1,1-trifluoroethane (HFC-143a), 1,1-difluoroethane (HFC-152a) and 1,1,1,2-tetrafluoroethane (HFC-134a), and the effect of $CO_2$ concentration on the phase behavior of $PMMA+HCFC-22+CO_2$ system and $PMMA+DME+CO_2$ system was observed. PMMA was dissolved well in HCFC-22 from about 340 K, 5MPa and in DME from about 300 K, 28MPa. However, PMMA was not dissolved at all up to 423.15 K, 160MPa in the other fluorine compound such as HFC-l43a, HFC-152a and HFC-134a. PMMA+HCFC-22, $PMMA+HCFC-22+CO_2$ and PMMA+DME systems exhibit the lower critical solution temperature (LCST) behavior, however, $PMMA+DME+CO_2$ system exhibits the upper critical solution temperature (UCST) behavior. In the $CO_2$ mixture, the cloud point pressure of PMMA was increased dramatically proportional to the amount of $CO_2$ added, and from this result, it was known that $CO_2$ could be used as an antisolvent for fabricating PMMA nano-particles. And the cloud point of PMMA could be controlled by changing the concentration of $CO_2$.

• Bulletin of the Korean Chemical Society
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• v.35 no.10
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• pp.3001-3004
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• 2014

A series of hydroxyl-derivatized quaternized polymers were successfully synthesized by atom transfer radical polymerization (ATRP) and Cu(I)-catalyzed 1,3-dipolar cycloaddition of azide and alkynes (click chemistry), followed by quaternization reactions. ATRP was employed to synthesize poly(2-hydroxyethyl methacrylate) (PHEMA), followed by introduction of alkyne groups using pentynoic acid, leading to HEMA-Alkyne. 2-Azido-1-ethanol and 3-azido-1-propanol were combined with the HEMA-Alkyne backbone via click reaction, resulting in triazole-ring containing hydroxyl-derivatized polymers. Quaternization reactions with methyl iodide were conducted on the triazole ring of each polymer. Molecular weight, molecular weight distribution, and the degree of quaternization (DQ) were determined by gel permeation chromatography (GPC) and $^1H$ NMR spectroscopy. The average molecular weight ($M_n$) of the resulting polymers ranged from $5.9{\times}10^4$ to $1.05{\times}10^5g/mol$ depending on the molecular architecture. The molecular weight distribution was low ($M_w/M_n$ = 1.26-1.38). The transmission spectra of the 0.1 wt % aqueous solutions of the resulting quaternized polymers at 650 nm were measured as a function of temperature. Results showed that the upper critical solution temperature (UCST) could be finely controlled by the level of DQ.

• Macromolecular Research
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• v.15 no.7
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• pp.640-645
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• 2007

The phase behavior of branched polycarbonate (BPC) blends with poly(ethylene terephthalate-co-1,4-dimethyl cyclohexane terephthalate) copolyesters (PECT), as well as their rheological properties, were assessed. Even though BPC blends with PECT prepared by solvent casting proved to be immiscible, BPC and PECT copolyesters containing 1,4-dimethyl cyclohexane (CHDM) from 32 to 80 mole% formed homogeneous mixtures upon heating. The homogenization temperatures of the blends decreased with increasing CHDM content in PECT. The interaction energies of the BPC-PECT pairs calculated from the phase boundary in accordance with the lattice-fluid theory were positive and also decreased with increasing CHDM content in PECT. It was shown that the phase homogenization of these blends occurs upon heating when the combinatorial entropy term, which is favorable for miscibility, overcomes unfavorable energetic terms at elevated temperatures. A novel product, which is not limited by the drawbacks of linear polycarbonate (PC) and evidences processability superior to that of the PC/PECT blends, can be developed via the blending of BPC and PECT.

• Polymer(Korea)
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• v.24 no.4
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• pp.488-498
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• 2000

Molecular bottle-brush was prepared by hydrogen-bonding between poly(4-vinylpyridine)(P4VP) as main chain and 3-pentadecylphenol (PDP) as amphiphilic side chain. Variation of long period ( $L_{p}$), order-disorder transition temperature ( $T_{ODT}$) and mesomorphic structure of bottle-brush were investigated by changing various mole ratio (x) of pyridine group in P4VP and PDP and molecular weight of P4VP. Upper critical solution temperature (UCST) behaviour was observed. For x 0.8-0.9, maximum critical temperature was found. As molecular weight of P4VP was increased, phase transition occurred at higher temperature. It was found that phase behaviour of the bottle-brush was affected by mobility of P4VP as well as size and regularity of lamellar structure. The $L_{p}$ determined from analysis of crystal structure was in the range of 35 $\AA$ and 40 $\AA$ and was more affected by the molecular weight of P4VP than by mole ratio (x). However, if the molecular weight of P4VP was high, LP value was little affected.ted.d.

• Korean Chemical Engineering Research
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• v.40 no.6
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• pp.703-708
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• 2002

High pressure phase behavior data for poly(propyl acrylate) and poly(propyl methacrylate) with supercritical $CO_2$, ethylene, propane, butane, propylene, 1-butene, dimethyl ether, and $CHClF_2$ were measured in the temperature range from $23^{\circ}C$ to $186^{\circ}C$ and at pressures up to 2,400 bar. The cloud point were obtained at dissolved pressure below 2,070, 1,400, 1,880, 450, 2,200, 250, and 150 bar for poly(propyl acrylate) in supercritical $CO_2$, ethylene, propane, propylene, butane, 1-buthen, and dimethyl ether, respectively. The temperature range is $23-175^{\circ}C$. The poly(propyl methacrylate) does not dissolve in $CO_2$ at temperature of $240^{\circ}C$ and pressure 2,900 bar. The poly(propyl methacrylate)-propane, poly(propyl methacrylate)-butane, poly(propyl methacrylate)-propylene, poly(propyl methacrylate)-1-butene, and poly(propyl methacrylate)-$CHClF_2$ systems were dissolved at the pressures less than 2,390 bar, below 2,100 bar, below 570 bar, below 310 bar, below 300 bar, and below 170 bar, respectively. The temperature range shows from 40 to $186^{\circ}C$. The phase behavior of between binary poly(propyl acrylate)-$CO_2$ and poly(propyl acrylate)-dimethyl ether system were measured from upper critical solution temperature region to lower critical solution temperature region with added dimethyl ether concentrations of 5, 15 and 50 wt%.