• Korean Chemical Engineering Research
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• v.47 no.4
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• pp.453-458
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• 2009

Recently, new methods to synthesize and process polymers without toxic organic solvents are needed in order to solve environmental problems. The use of supercritical carbon dioxide as a solvent for the polymer synthesis is attractive since it is non-toxic, non-flammable, naturally abundant, and the product may be easily separated from the solvent. In this study, we developed the method using super critical $CO_2$ to prepare P(MAA-co-EGMA) hydrogel nanoparticles as an intelligent drug delivery carrier. The effects of concentrations of PtBuMA-PEO as a dispersion stabilizer and AIBN as an initiator on the particle synthesis were investigated. When PtBuMA-PEO concentration increased, the particle size decreased. However, there was no significant difference in the particle size according to the AIBN concentration. There was a drastic change of the equilibrium weight swelling ratio of P(MAA-co-EGMA) hydrogel nanoparticles at a pH of around 5, which is the $pK_a$ of PMAA. At a pH below 5, the hydrogels were in a relatively collapsed state but at a pH higher than 5, the hydrogels swelled to a high degree. In release experiments using Rh-B as a model solute, the P(MAA-co-EGMA) hydrogel nanoparticles showed a pH-sensitive release behavior. At low pH(pH 4.0) a small amount of Rh-B was released while at high pH(pH 6.0) a relatively large amount of Rh-B was released from the hydrogels.

• Applied Chemistry for Engineering
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• v.24 no.4
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• pp.396-401
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• 2013

Alternating copolymers, poly[9-(2-octyl-dodecyl)-9H-carbazole-alt-4,7-di-thiophen-2-yl-benzo[1,2,5]thiadiazole] (PCD20TBT) and poly[9,10-bis-(2-octyl-dodecyloxy)-phenanthrene-alt-4,7-di-thiophen-2-yl-benzo[1,2,5]thiadiazole] (PN40TBT), were synthesized by the Suzuki coupling reaction. The copolymers were soluble in common organic solvents such as chloroform, chlorobenzene, 1,2-dichlorobenzene, tetrahydrofuran and toluene. The maximum absorption wavelength and the band gap of PCD20TBT were 535 nm and 1.75 eV, respectively. The maximum absorption wavelength and the band gap of PN40TBT were 560 nm and 1.97 eV, respectively. The HOMO and the LUMO energy level of PCD20TBT were -5.11 eV and -3.36 eV, respectively. As for PN40TBT, the HOMO and the LUMO energy level of PCD20TBT were -5.31 eV and -3.34 eV, respectively. The polymer solar cells (PSCs) based on the blend of copolymer and PCBM (1 : 2 by weight ratio) were fabricated. The power conversion efficiencies of PSCs based on PCD20TBT and PN40TBT were 0.52% and 0.60%, respectively. The short circuit current density ($J_{SC}$), fill factor (FF) and open circuit voltage ($V_{OC}$) of the device with PCD20TBT were $-1.97mA/cm^2$, 38.2% and 0.69 V. For PN40TBT, the $J_{SC}$, FF, and $V_{OC}$ were $-1.77mA/cm^2$, 42.9%, and 0.79 V, respectively.

• Applied Chemistry for Engineering
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• v.24 no.5
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• pp.537-543
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• 2013

In this study, the push-pull structure polymer for organic photo voHaics (OPVs) was synthesized and characterized. The poly{4,8-didodecyloxybenzo[1,2-b;3,4-b]dithiophene-alt-5,6-bis(octyloxy)-4,7-di(thiophen-2-yl)benzo[c][1,2,5]-thiadiazole} (PDBDT-TBTD) was synthesized by Stille coupling reaction using the benzothiadiazole (BTD) derivative as an electron acceptor and benzodithiophene (BDT) derivative as an electron donor. The structure of monomers and polymers was identified by $^1H-NMR$ and GC-MS. The optical, physical and electrochemical properties of the conjugated polymer were identified by GPC, TGA, UV-Vis and cyclic voltammetry. The number average molecular weight ($M_n$) and initial decomposition temperature (5% weight loss temperature, $T_d$) of PDBDT-TBTD were 6200 and $323^{\circ}C$, respectively. The absorption maxima on the film was about 599 nm and the optical band gap was about 1.70 eV. The structure of device was ITO/PEDOT : PSS/PDBDT-TBTD : $PC_{71}BM/BaF_2/Ba/Al$. PDBDT-TBTD and $PC_{71}BM$ were blended with the weight ratio of 1:2 which were then used as an optical active layer. The power conversion efficiency (PCE) of fabricated device was measured by solar simulator and the best PCE was 2.1%.

• Journal of Navigation and Port Research
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• v.38 no.3
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• pp.239-246
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• 2014

A study on the elution characteristics of biostimulating agents (sulfate and nitrate) from biostimulants which are used for in-situ bioremediation for the coastal sediment contaminated with organic matter was performed. The biostimulating agents were mixed with the coastal sediment, and then massed the mixture into ball. Two kinds of ball type biostimulant were prepared by coating the ball surface with two different polymers, cellulose acetate and polysulfone. A granular type biostimulant (GTB) was also prepared by impregnating a granular activated carbon in the biostimulating agent solution. The image of scanning electron microscopy for the biostimulant coated with cellulose acetate (CAB) showed that the inner side of the coating layer consisted of irregular and bigger size of pores, and the surface layer had tight structure like beehive. For the biostimulant coated with polyfulfone (PSB), the whole coating layer had a fine structure without pore. The elution rate of the biostimulating agents for the CAB was higher than that for the PSB, and the elution rate for the GTB was considerably higher than that for the PSB in distilled water as well as in sea water. The elution rate of the biostimulating agents in turbulent water flow was about 3 times higher than that in standing water, and the elution rate of nitrate was higher than that of sulfate from the stimulating agents.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2009.06a
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• pp.84-85
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• 2009

New approaches for detecting, preventing and remedying environmental damage are important for protection of the environment. Procedures must be developed and implemented to reduce the amount of waste produced in chemical processes, to detect the presence and/or concentration of contaminants and decontaminate fouled environments. Contamination can be classified into three general types: airborne, surface and structural. The most dangerous type is airborne contamination, because of the opportunity for inhalation and ingestion. The second most dangerous type is surface contamination. Surface contamination can be transferred to workers by casual contact and if disturbed can easily be made airborne. The decontamination of the surface in the nuclear facilities has been widely studied with particular emphasis on small and large surfaces. The amount of wastes being produced during decommissioning of nuclear facilities is much higher than the total wastes cumulated during operation. And, the process of decommissioning has a strong possibility of personal's exposure and emission to environment of the radioactive contaminants, requiring through monitoring and estimation of radiation and radioactivity. So, it is important to monitor the radioactive contamination level of the nuclear facilities for the determination of the decontamination method, the establishment of the decommissioning planning, and the worker's safety. But it is very difficult to measure the surface contamination of the floor and wall in the highly contaminated facilities. In this study, the poly(styrene-ethyl acrylate) [poly(St-EA)] core-shell composite polymer for measurement of the radioactive contamination was synthesized by the method of emulsion polymerization. The morphology of the poly(St-EA) composite emulsion particle was core-shell structure, with polystyrene (PS)as the core and poly(ethyl acrylate) (PEA) as the shell. Core-shell polymers of styrene (St)/ethyl acrylate (EA) pair were prepared by sequential emulsion polymerization in the presence of sodium dodecyl sulfate (SOS) as an emulsifier using ammonium persulfate (APS) as an initiator. The polymer was made by impregnating organic scintillators, 2,5-diphenyloxazole (PPO) and 1,4-bis[5-phenyl-2-oxazol]benzene (POPOP). Related tests and analysis confirmed the success in synthesis of composite polymer. The products are characterized by IT-IR spectroscopy, TGA that were used, respectively, to show the structure, the thermal stability of the prepared polymer. Two-phase particles with a core-shell structure were obtained in experiments where the estimated glass transition temperature and the morphologies of emulsion particles. Radiation pollution level the detection about under using examined the beta rays. The morphology of the poly(St-EA) composite polymer synthesized by the method of emulsion polymerization was a core-shell structure, as shown in Fig. 1. Core-shell materials consist of a core structural domain covered by a shell domain. Clearly, the entire surface of PS core was covered by PEA. The inner region was a PS core and the outer region was a PEA shell. The particle size distribution showed similar in the range 350-360 nm.

• Journal of Pharmaceutical Investigation
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• v.36 no.4
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• pp.271-276
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• 2006

Felodipine, a calcium-antagonist of dihydropyridine type, is a poorly water soluble drug and has very low bioavailability. As preceding studies, use of solid dispersion systems and surfactants(solubilizers) has been suggested to increase dissolution and to improve bioavailability of felodipine. But in case of solid dispersion systems, large amount of toxic organic solvents should be used and manufacturing process time become longer than conventional process. In case of using surfactants, as time elapsed, decreasing of dissolution rate of felodipine due to crystallization has been reported. In this study, Copovidon as a hydrophilic polymer and $Transcutol^{\circledR}$ as a surfactant were combined to formulations if order to increase dissolution of felodipine and conventional wet granulation process were applied to manufacturing of formulations. The effect of Copovidon and $Transcutol^{\circledR}$ on the dissolution oi felodipine was investigated in-vitro. When Copovidon and $Transcutol^{\circledR}$ used simultaneously, the dissolution rate of felodipine was prominently increased compared with when used separately and the maximum increase in the dissolution of felodipine was 5.8 fold compared to control. This is most probably due to synergy effect by combination of Copovidon and $Transcutol^{\circledR}$. Felodipine sustained release tablets were successfully formulated using several grades of HPMC as a release retarding agent. The stability of felodipine sustained release tablet was evaluated after storage at accelerated condition($40^{\circ}C/75%\;RH$) for 6months in HDPE(High density polyethylene) bottle. Neither significant degradation nor change of dissolution rate for felodipine was observed after 6months. In conclusion, felodipine sustained release tablet was successfully formulated and dissolution of felodipine, poorly water soluble drug, was prominently increased and also stability was guaranteed by using combination system of hydrophilic polymer and surfactant.

• Applied Chemistry for Engineering
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• v.25 no.6
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• pp.624-631
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• 2014

In this study, a new series of conjugated polymer 3-(5-(5,6-bis(octyloxy)-7-(thiophen-2-yl)benzo[c][1,2,5]thiadiazol-4-yl)thiophen-2-yl)-10-(4-(octyloxy)phenyl)-10H-phenothiazine (P1) and 3-(5-(5,6-bis(octyloxy)-7-(thiophen-2-yl)benzo[c][1,2,5]thiadiazol-4-yl)thiophen-2-yl)-10-(4-((2-ethylhexyl)oxy)phenyl)-10H-phenothiazine (P2) were synthesised and organic photovoltaics (OPVs) properties were characterized. The push-pull structure polymer consisted of phenothiazine derivative as an electron donor and benzothiadiazole derivative as an electron acceptor. The aliphatic chain substituted aromatic ring was substituted at the position of N in phenothiazine for the electron-rich and improved solubility. Excellent thermal stabilities of P1 and P2 were confirmed by measured Td values as 321.9 and $323.7^{\circ}C$, respectively and the degrees of polymerization were 4,911 (P1) and 5,294 (P2). The maximum absorption wavelength of P1 and P2 were 549 and 566 nm, respectively. The device was fabricated and the OPVs property was measured. As a result, the power efficiency of conversion for P1 and P2 were 0.96 and 0.90%, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.4
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• pp.51-56
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• 2006

Polymer light emitting diodes (PLEDs) with ITO/EDOT:PSS/PVK/PFO-poss/LiF/Al structures were prepared by the spin coating method on ITO(indium tin oxide)/glass substrates. PFO-poss[Poly(9,9-dioctylfluorenyl-2,7-diyl) end capped with poss] was used as light emitting polymer. PVK[poly(N-vinyl carbazole)] and PEDOT:PSS [poly(3,4-ethylenedioxythiophene):poly(styrene sulfolnate)] polymers were used as the hole injection and transport materials. The effect of PFO-poss concentration and the heating temperatures on the electrical and optical properties of the devices were investigated. At the same concentration of PFO-poss solution, the current density and luminance of PLED device tend to increase as the annealing temperature increase from $100^{\circ}C$ to $200^{\circ}C$. The maximum luminance was found to be about 958 cd/m2 at 13V for the PLED device with 1.0 wt% PFO-poss at the annealing temperature of $200^{\circ}C$. In addition, the PLED device showed bluish white emission through the strong greenish peak with 523 nm in wavelength. As the concentration of PFO-poss increase from 0.5 wt% to 1.0 wt% and temperature of PLEDs increase from $100^{\circ}C$ to $200^{\circ}C$, the emission color tend to be shifted from blue with (x, y) = (0.17,0.14) to bluish white with (x, y) : (0.29,0.41) in CIE color coordinate.

• Polymer(Korea)
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• v.30 no.2
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• pp.140-145
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• 2006

The mort commonly available substrate material is glass in the display fibrication process. However, glass is not desirable due to its heaviness and fragility. Recently, plastics such polysulfone (PSF), polyethesulfone (PES), polycarbonate (PC), polyethylene terephthalate (PET) and cyclic olefin polymers (COP) have been investigated to replace glass as a substrate material for display fibrication. Plastic substrates are advantageous in that they are lightweight, huh impart resistance, flexibility, and ability for roll to roll manufacturing process. But many plastics have poor chemical resistance in organic solvent. The chemica resistance is also lequired because they are exposed to solvents for various chemical treatments din the manufacturing process. So, we have an interest in the chemical modification of PSF to improve chemical resistance. We introduced crosslinkable imide moieties using chloromethylation method for the modification of PSF which could be overcome above shortcomings for display substrate based on plastic film. We prepared the cross-linked polysulfone films which were represented chemical resistance in HeOH, THF, DMSO and NMP. The thermal properties were measured by TGA, DSC and TMA. As the results, we have confirmed to enhance of the thermal property. They had low coefficient of thermal expansion (CTE) which decreased to 15% and had increased $T_g\;from\;180^{\circ}C\;to\;252^{\circ}C$. Cross-linked polysulfone films with imide side-chain had good optical properties and chemical resistance so that they could be used as flexible display substrate.

• Elastomers and Composites
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• v.42 no.4
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• pp.238-248
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• 2007

A series of polyhydroxyamides(PHAs) having ether linkages in the polymer backbone were prepared via solution polycondensation at low temperature. These polymers were studied by FT-IR, $^1H-NMR$, DSC, TGA and PCFC. The PHAs exhibited inherent viscosities in the range of $0.5{\sim}1.1dL/g\;at\;35^{\circ}C$ in DMAc solution. Most of PHAs except PHA 3 were soluble in polar organic solvents such as N,N-dimethylacetamide(DMAc), N-methyl-2-pyrrolidone(NMP), and N,N-dimethylform-amide(DMF). Subsequent thermal treatment of PHAs afforded polybenzoxazols(PBOs). However, the PBOs were insoluble in a variety of solvents. Most of the PBOs except PBO 3 showed glass-transition temperature($T_g$) in the range of $200{\sim}246^{\circ}C$ by DSC and maximum weight loss temperature in the range of $597{\sim}697^{\circ}C$ in nitrogen by TGA. PBOs showed high char yields in the range of $51{\sim}64%$. PCFC results of the PBOs showed the heat release(HR) capacity, $8{\sim}65J/gK$ and total heat release(total HR), $2.4{\sim}4.7kJ/g$.