• Macromolecular Research
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• v.13 no.5
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• pp.397-402
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• 2005

To explore the potential of shell crosslinked micelle (SCM) as a drug carrier, the drug release behavior of poly($\varepsilon$-caprolactone)-b-poly(acrylic acid) (PCL-b-PAA) SCMs was investigated. PCL-b-PAA was synthesized by ring opening polymerization of $\varepsilon$-caprolactone and atom transfer radical polymerization of tert-butyl acrylate, followed by selective hydrolysis of tert-butyl ester groups to acrylic acid groups. The resulting amphiphilic polymer was used to prepare SCMs by crosslinking of PAA corona via amidation chemistry. The drug release behavior of the SCMs was studied, using pyrene as a model drug, and was compared with that of non-crosslinked micelles, especially below the critical micelle concentration (CMC). When the shell layers were crosslinked, the drug release behavior of the SCMs was successfully modulated at a controlled rate compared with that of the non-crosslinked micelles, which showed a burst release of drug within a short time.

• Membrane and Water Treatment
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• v.6 no.3
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• pp.173-187
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• 2015

The goal of present work is the preparation of a novel positively charged nanofiltration (NF) membrane and its development for the cation removal of aqueous solutions. This NF membrane was fabricated by the surface modification of polysulfone (PSf) ultrafiltration support. The active top-layer was formed by interfacial cross-linking polymerization of poly(ethyleneimine) (PEI) with p-xylylene dichloride (XDC) and then quaternized with methyl iodide to form a perpetually positively charged layer. In order to improve the efficiency of nanofiltration membrane, the concentration of PEI, XDC and methyl iodide solutions, PEI coating and cross-linking time have been optimized. As a result, a high water flux and high $CaCl_2$ rejection (1,000 ppm) was obtained for the composite membrane with values of $18.29L/m^2.h$ and 93.62% at 4 bar and $25^{\circ}C$, respectively. The rejections of NF membrane for different salt solutions followed the order of $Na_2SO_4$ < $MgSO_4$ < NaCl < $CaCl_2$. Molecular weight of cut off (MWCO) was calculated via retaining of PEG solutions with different molecular weights that finally, it revealed the Stokes and hydrodynamic radius of 1.457 and 2.507 nm on the membrane selective layer, respectively. The most efficient positively charged nanofiltration membrane exhibited a $Ni^{2+}$ rejection of 96.26% for industrial wastewater from Shamse Hadaf Co. (Kashan, Iran).

• Macromolecular Research
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• v.12 no.1
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• pp.107-111
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• 2004

We have studied the polymerization kinetics of acrylamide in aqueous solution with potassium persulfate as an initiator by using quantitative real-time in situ IR spectroscopy and monitoring the profiles of peaks in the range 1900-850 cm$\^$-1/. The conversion of acrylamide was calculated from the disappearance of the peak at 988 cm$\^$-1/, which is the out-of-plane bending mode of the=C-H unit, normalized to the C=O stretching peak at 1675 cm$\^$-1/, as an internal standard. For reaction temperatures in the range 40-65$^{\circ}C$ and initiator and monomer concentrations of 0.9-2.6 mmol/L and 0.5-1.1 mol/L, respectively, we deduced that the rate of monomer consumption follows the relation R$\_$p/=k［K$_2$S$_2$O$\_$8/］$\^$0.5/ [Μ］$\^$1.35${\pm}$0.10/. In addition, we obtained activation parameters from an evaluation of the kinetic data.

• Elastomers and Composites
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• v.11 no.1
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• pp.54-62
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• 1976

It has been studied the graft copolymerization of glycidyl-methacrylate monomer containing two functional groups (vinyl- & epoxyl-) to chloroprene rubber. The reaction occured in the manner of chain transfer mechanism was carried out by means of solution polymerization in toluene in the presence of benzoyl peroxide as the radical initiator. The graft copolymer obtained from this work was analyzed by using IR spectrum, and the physical properties of the polymer such as the thermal behavior were also studied according to TG-DTA methods, and the potency of adhesiveness for the purpose of commercial application was investigated. Experimental results for the graft copolymerization are summarized as follows. 1) A small amount of initiator (0.5%) and 50% of monomer showed the best result for the grafting of monomer to the polymer chain of rubber while the 15% of rubber solution was found to be most suitable to raise either for the grafting ratio or the polymerization ratio. 2) Optimum temperature for better yield of graft copolymer was proved to he at $75^{\circ}C\sim80^{\circ}C$ while those of reaction time was to be $1\sim2$ hours.

• Polymer(Korea)
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• v.34 no.4
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• pp.381-385
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• 2010

Aiphatic diester monomer, 3-[(benzyloxycarbonylamino)butyl]-1,4-dioxane-2,5-dione (BABD), was synthesized with the N-$\varepsilon$-benzyloxy-carbonyl-L-lysine as starting material. This monomer was synthesized to add the functionality to poly(lactic acid)s. BABD unit was successfully incorporated into the PLLA chain which was confirmed by $^1H$ NMR. The copolymer composition could be controlled by the feed ratios of monomer. The $M_n$ of this resultant polymer is expected to reach high molecular weight after the purification of monomer and optimization of polymerization time, though the polymer showed relatively low degree of polymerization ($M_n$＝3300). The copolymer is expected to possess the enhanced hydrophilicity and the possibility of chemical modification on amino group.

• Elastomers and Composites
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• v.56 no.3
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• pp.152-163
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• 2021

Liquid butadiene rubber (LqBR) is used as a processing aid and plays a vital role in the manufacture of high-performance tire tread compounds. In this study, center-functionalized LqBR (C-LqBR) was polymerized with different vinyl content via anionic polymerization. The effects of the vinyl content on the properties of the compounds were investigated by partially replacing the treated distillate aromatic extract (TDAE) oil with C-LqBR in silica-filled rubber compounds. C-LqBR compounds showed a low Payne effect and Mooney viscosity regardless of the vinyl content, because of improved silica dispersion due to the ethoxysilyl group. As the vinyl content of C-LqBR increased, the optimum cure time (t₉₀) increased owing to a decrease in the number of allylic hydrogen. Moreover, the glass transition temperature (T_g) of the compound increased, and snow traction and abrasion resistance performance decreased, whereas wet grip improved. The energy loss characteristics revealed that the hysteresis attributed to the free chain ends of C-LqBR was dominant.

• Applied Chemistry for Engineering
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• v.22 no.4
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• pp.444-446
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• 2011

Nanosized polystyrene (PS) particles with the narrow size distribution were synthesized from styrene monomer at the presence of the surfactant (polyvinylpyrrolidone, PVP), the solvent of 95 % alcohol, and the initiator of benzoyl peroxide (BPO). Since the emulsion polymerization method was applied, many factors could have effects on the size of PS particles during polymeric process. Aside from the concentration of monomer, surfactant and initiator, the factors such as the stirring speed and the ultrasonic radiation were mainly studied. By adjusting the radiating time, PS particles with their size of about 400 nm were synthesized.

• Membrane and Water Treatment
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• v.13 no.2
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• pp.105-110
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• 2022

Al₂O₃ positively charged nanofiltration composite membrane was successfully prepared with aluminate coupling agent (ACA) as modifier, sodium bisulfite (NaHSO₃) and potassium persulfate (K₂S₂O₈) as initiator and methacryloyloxyethyl trimethylammonium chloride (DMC) as crosslinking monomer. The surface of the membrane before grafting and after polymerization were characterized by SEM and FT-IR. Three factor and three-level orthogonal experiments were designed to explore the optimal conditions for membrane preparation, and the optimal group was successfully prepared. The filtration experiments of different salt solutions were carried out, and the retention molecular weight was determined by polyethylene glycol (PEG). The results showed that the polymerization temperature had the greatest effect on the rejection rate, followed by the reaction time, and the concentration of DMC had the least effect on the rejection rate. The rejection rates of CaCl₂, MgSO₄, NaCl and Na₂SO₄ in the optimal group were 83.8%, 81.3%, 28.1% and 23.6% (average value), respectively. The molecule weight cut-off of 90% (MWCO) of the optimal group was about 460, which belongs to nanofiltration membrane.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.622-624
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• 2003

Poly(lactic acid) is a biodegradable themoplastic based on the renewable resources to substitute for petrochemical plastics. Most of PLA is produced by ring opening polymerization from lactide. However, pyrolysis process in the lactide synthesis is expensive, we studied lactide synthetic process for more economical preparation of PLA. In this research was tried to minimize the pyrolysis time, and obtained L-lactide from lactic acid without any catalyst.

• Proceedings of the KACD Conference
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• 2001.11a
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• pp.586.2-586
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• 2001

The selection of a curing light is a multifactorial decision. While each method of polymerization presents unique clinical benefits, the optimal light-curing technique remains to be determined. The objective of this study was to check the difference of micro hardness and microleakage according to various light intensity (50, 100, 200, 300, 400, 600 ㎽/$\textrm{cm}^2$) and curing time (10, 20, 40 seconds). A3 color of two composite resin, hybrid type DenFil and submicron type Esthet X were tested.(중략)