• Proceedings of the Membrane Society of Korea Conference
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• 1995.10a
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• pp.54-55
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• 1995

현재 수처리용 분리막으로 널리 사용되고 있는 상업용 polyamide membrane은 주사슬을 이루고 있는 amide bond가 chlorine에 쉽게 분해됨으로써 주쇄의 절단이 일어나므로 막이 파괴되는 결과를 초래하여 역삼투 분리막의 기능이 저하되는 문제점을 갖고 있다. 또한 분리막의 성능으로써 수투과도의 향상도 기존의 분리막의 개선점으로 지적되고 있다. 본 연구에서는 재료 자체의 친수성이 강한 hydroxyl group을 가진 vinyl계 화합물을 기존의 amine계 monomer와 혼합하여 가교반응을 시킴으로써 전체적인 분리막의 수투과도 및 내염소성의 향상을 도모하였다. 기존의 polyamide 분리막의 소재인 1,3-phenylenediamine(MPDA)에 친수성기인 hydroxyethylmethacrylate(HEMA) monomer를 첨가하고 가교제인 trymesoyl chloride(TMC)로 이를 가교시켜 HEMA 및 PVA의 친수성에 의한 수투과도 및 내염소성의 향상을 유도하여 보았다.

• Korean Journal of Materials Research
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• v.14 no.5
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• pp.363-367
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• 2004

Recently ZnO epitaxial layers have been widely studied as a semiconductor material for optoelectronic devices. Sapphire and silicon are commonly selected as substrate materials for ZnO epitaxial growth. In this communication, we report the effect of the ECR plasma pretreatment of sapphire and silicon substrates on the nucleation in the ZnO ALE (atomic layer epitaxy). It was found that ECR plasma pretreatment reduces the incubation period of the ZnO nucleation. Oxygen ECR plasma enhances ZnO nucleation most effectively since it increases the hydroxyl group density at the substrate surface. The nucleation enhancing effect of the oxygen ECR plasma treatment is stronger on the sapphire substrate than on the silicon substrate since the saturation density of the hydroxyl group is lower at the sapphire surface than that at the silicon surface.

• Journal of the Korean Vacuum Society
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• v.9 no.1
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• pp.24-29
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• 2000

MgO thin films were deposited on soda lime glass substrates by rf magnetron sputtering using a MgO target at various oxygen flow ratios in order to probe the relationship between MgO film properties and discharge characteristics. MgO films have a tendency to form microstructures with a preferred growth orientation of (200) with increasing oxygen flo ration up to 0.1 $O_2$/(Ar+$O_2$). MgO film obtained at 0.1[$O_2$/(Ar+$O_2$)] was found to be fully stoichiometric. The stoichiometric MgO film was observed to have relatively very clean surface and grains of large size and contain almost no hydroxyl group. The AC PDP with fully stoichiometric MgO film showed lower firing and sustain voltages than those with magnesium-rich or oxygen-rich MgO films, being largely attributed to the larger grain size and the minimized hydroxyl group.

• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2694-2698
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• 2014

A multisegmented polystyrene (PS) with pH-cleavable ester and carbamate linkages was successfully synthesized by a combination of atom transfer radical polymerization (ATRP) and Cu(I)-catalyzed 1,3-dipolar cycloaddition of azide and alkynes (click chemistry). ATRP was employed to synthesize polystyrene from hydroxyl-terminated initiator using CuBr/N,N,N',N",N"-pentamethyldiethylenetriamine (PMDETA) as the catalyst. The reaction of the resulting PS with sodium azide yielded the azido-terminated polymer. The hydroxyl group in the other end of the polymer was reacted with 4-nitrophenyl chloroformate (NPC), followed by reaction with propargylamine to produce an alkyne end group with a carbamate linkage. The PS with an alkyne group in one end and an azide group in the other end was then self-coupled in the presence of CuBr/2,2'-bipyridyl (bpy) in DMF to yield a desired multisegmented PS. Molecular weight and molecular weight distribution of the self-coupled polymer increased with time, as in the typical step-growth-type polymerization processes. Finally, we demonstrated that the ester and carbamate linkages of the multisegmented PS were hydrolyzed in the presence of HCl to yield individual PS chains.

• Bulletin of the Korean Chemical Society
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• v.19 no.5
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• pp.569-575
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• 1998

Investigation of the structure of the gangliosides has proven to be very important in the understanding of their biological roles. We have determined the tertiary structure of asialoganglioside GM1 $(GA_1)$ using NMR spectroscopy and distance geometry calculations. All of the structures are very similar except the glycosidic torsion angles in the ring IV and ring III linkages. There are two low-energy structures for GA1, G1 and G2. G1 differs from G2 only in the IV-III glycosidic linkages and the orientation of acetamido group in ring III. There is a stable intramolecular hydrogen bond between the third hydroxyl group in ring I and the ring oxygen atom in ring II. Also, there may be a weak hydrogen bond between the second hydroxyl group in ring IV and the acetamido group in ring III. Small coupling constants of $^3J_{IH3,IOH3}\; and\; ^3J_{IVH2,IVOH2}$ support this result. Overall structural features of $(GA_1)$ are very similar to those of $(GM_1)$. It implicates that specificities of the sugar moieties in GM1 are caused not by their tertiary foldings, but mainly by the electrostatic interactions between the polar sialic acid and its receptors. Since it is evident that $(GA_1)$ is more hydrophobic than $(GA_1)$, a receptor with a hydrophobic binding site can recognize the $(GA_1)$ better than $(GA_1)$. Studies on the conformational properties of $(GA_1)$ may lead to a better understanding of the molecular basis of its functions.

• Environmental Engineering Research
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• v.24 no.1
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• pp.173-179
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• 2019

Prussian blue (PB) is known to be an effective material for radioactive cesium adsorption, but its nano-range size make it difficult to be applied for contaminated water remediation. In this study, a simple and versatile approach to immobilize PB in the supporting matrix via surface functionalization was investigated. The commercially available poly vinyl alcohol (PVA) sponge was functionalized by acrylic acid (AA) to change its major functional group from hydroxyl to carboxylic, which provides a stronger ionic bond with PB. The amount of AA added was optimized by evaluating the weight change rate and iron(III) ion adsorption test. The FTIR results revealed the surface functional group changing to a carboxyl group. The surface functionalization enhanced the attachment of PB, which minimized the leaching out of PB. The $Cs^+$ adsorption capacity significantly increased due to surface functionalization from 1.762 to 5.675 mg/g. These findings showed the excellent potential of the PB-PAA-PVA sponge as a cesium adsorbent as well as a versatile approach for various supporting materials containing the hydroxyl functional group.

• Bulletin of the Korean Chemical Society
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• v.18 no.12
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• pp.1236-1238
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• 1997

• Bulletin of the Korean Chemical Society
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• v.13 no.3
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• pp.222-223
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• 1992

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.2
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• pp.262-267
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• 2013

The purpose of this research is to minimize the loss of nutrients in carrots (Daucus carota var. sativa). A protopectinase was used to enzymatically macerated and separate cells without damage. The enzyme modification group's collection rate was 81% (residue rate 19%), while the grinding process group's collection rate was 56% (residue rate 44%)-an over 20% of collection rate difference. Thus we predicted a big difference in transference number after the process and wastage. In comparing ingredient changes in the enzyme modification group versus the grinding process group, the content of ${\beta}$-carotene (the carrot's main ingredient) showed a change in protection factor (PF) ($2.2{\pm}0.2$ PF, $1.4{\pm}0.4$ PF, respectively), total polyphenol content ($89{\pm}3.42{\mu}g/g$, $64{\pm}4.16{\mu}g/g$, respectively), and total flavonoid content ($68{\pm}2.73{\mu}g/g$, $41{\pm}3.26{\mu}g/g$, respectively). Thus we confirmed that nutrient destruction, due to cell membrane preservation, occurred less often in the enzyme modification process than the mechanical grinding process group. We also measured DPPH radical scavenging activity, hydroxyl radical scavenging activity, and nitrite scavenging activity. DPPH radical scavenging activity was $87{\pm}0.29%$ and $74{\pm}1.56%$ in the enzymatic modification group compared to the mechanical grinding process group, respectively. Hydroxyl radical scavenging activity was $44{\pm}0.49%$ and $32{\pm}0.48%$ in the enzymatic modification group compared to the mechanical grinding process group, respectively. Nitrite scavenging activity was $59{\pm}0.53%$ and $46{\pm}0.62%$ in the enzymatic modification group compared to the mechanical grinding process group, respectively. Our results show that cell membrane preservation, via the protopectinase enzyme process, decreases the loss of nutrients and still preserves inherent antioxidants.

• Journal of the Korean Wood Science and Technology
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• v.45 no.4
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• pp.432-443
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• 2017

Maltodextrin and citric acid are two types of natural materials with the potential as an eco-friendly binder. Maltodextrin is a natural substance rich in hydroxyl groups and can form hydrogen bonds with lignoselulosic material, while citric acid is a polycarboxylic acid which can form an ester bond with a hydroxyl group at lignoselulosic material. The combination of maltodextrin and citric acid as a natural binder materials supposed to be increase the ester bonds formed within the particleboard. This research determined to investigate the bonding properties of a new adhesive composed of maltodextrin/citric acid for nipa frond particleboard. Maltodextrin and citric acid were dissolved in distillated water at the ratios of 100/0, 87.5/12.5, 75/25 and 0/100, and the concentration of the solution was adjusted to 50% for maltodextrin and 60% citric acid (wt%). This adhesive solution was sprayed onto the particles at 20% resin content based on the weight of oven dried particles. Particleboards with a size of $25{\times}25{\times}1cm$, a target density $800kg/m^3$ were prepared by hot-pressing at press temperatures of $180^{\circ}C$ or $200^{\circ}C$, a press time of 10 minute and board pressure 3.6 MPa. Physical and mechanical properties of particleboard were tested by a standard method (JIS A 5908). The results showed that added citric acid level in maltodextrin/citric acid composition and hot-pressing temperature had affected to the properties of particleboard. The optimum properties of the board were achieved at a pressing temperature of $180^{\circ}C$ and the addition of only 20% citric acid. The results also indicated that the peak intensity of C=O group increased and OH group decreased with the addition of citric acid and an increase in the pressing temperature, suggesting an interreaction between the hydroxyl groups from the lignocellulosic materials and carboxyl groups from citric acid to form the ester groups.