• Journal of the Korean Chemical Society
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• v.37 no.1
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• pp.22-35
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• 1993

The transport phenomena of the free amino acids through poly(hydroxyethyl methacrylate)[P(HEMA)] have been investigated with and without various kinds of surfactants solution and in the mixed surfactants solution. Glutamine has the highest diffusivity among 4 amino acids at 1CMC of cetyldimethylethylammonium bromide(CTABr) surfactant. Glutamic acid is not affected by the concentration of CTABr. Methionine and Lysine shows slight decreased diffusivity at 0.5 CMC, but increase its diffusivity at 1CMC and 2CMC due to the structure change of membrane and the viscosity change of surfactant solution. Glutamic acid has the highest diffusivity among four amino acids at sodium dodecyl sulfate(SDS) and Triton X-100 surfactant. In mixed surfactant solution, each amino acids shows high diffusivity through 45% water content membrane at the 0.5 mole fraction of SDS in the SDS/TX-100 surfactant mixtures. It has been found that not only the property of membrane but also the effects of solute-solvent interactions and solvent effect are very important as the permeation of amino acids occurs through P(HEMA) membrane. The diffusivities of free amino acids through membrane depend upon their molecular shape, size and charge.

• Applied Chemistry for Engineering
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• v.19 no.1
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• pp.51-58
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• 2008

A series of oleic acid esters containing mercaptobenzothiazole and dialkylenedithiocarbamate, which are potential environmentally friendly lubricating grease additives, were synthesized as 90% yield through several method such as nucleophilic substitution of dialkyl amine and carbon disulfide, reduction reaction, and condensation reaction. The structures of the additives were confirmed by $^1H$-NMR, FT-IR and EA analysis. The additives (1 wt%) were soluble in 100 N BO except C4-DTC-OE and soluble in soybean oil. The tribological properties as lubricating additives in 100 N BO were evaluated using 4-ball tester and the results showed as follows: Bz-thia-OE < C4-DTC-OE < Pyrro-DTC-OE < C8-DTC-OE. Whereas, the 4-ball anti-wear properties were not shown in soybean oil.

• Applied Chemistry for Engineering
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• v.22 no.4
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• pp.367-375
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• 2011

Succinic acid ester derivatives have been used as additives for the base oil of metal working fluids and pressure working oils. In this paper, a series of succinic acid alkyl half-esters were synthesized with over 97% yields by ring-opening reaction of succinic anhydride and fatty alcohol and were soluble in 100 N base oil within 1 wt% concentration. The structures and purities of ester derivatives were confirmed by $^1H-NMR$ and FT-IR spectrum and GC analysis. Anti-corrosion properties of the esters in sea water were evaluated through ASTM D665 method and weight loss method and compared to that of succinic alkyl esters without carboxylic acid group in the molecule. As the results, anti-corrosion properties of succinic acid alkyl half-esters with carboxylic acid group were better than those of succinic acid alkyl esters without carboxylic acid group. And, Anti-corrosion properties of the esters with a shorter alkyl chain of high concentration showed better performance than those with longer alkyl chain of low concentration. Inhibition efficiency % (IE%) of the esters was over 95% in the concentration of 80 ppm and corrosion rate (CR) was below 0.3 mm/year at the same concentration. Thus, the corrosion properties of succinic acid alkyl half-esters result from the carboxylic acid groups in molecules.

• Applied Chemistry for Engineering
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• v.22 no.4
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• pp.416-422
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• 2011

In this study, the effect of cosurfactant on the phase equilibrium and dynamic behavior was studied in systems containing NP7 nonionic surfactant solutions and nonpolar hydrocarbon oils. All cosurfactants used during this study such as n-pentanol, n-octanol and n-decanol acted as a hydrophobic additive and thus promoted the transition from an oil in water (O/W) microemulsion (${\mu}E$) in equilibrium with an excess oil phase to a three-phase region containing excess water, excess oil, and a middle-phase microemulsion and further to a water in oil (W/O) ${\mu}E$ in equilibrium with the excess water phase. The transition temperature was found to decrease with both increases in the chain length and amount of addition of a cosurfactant. Dynamic behavior studies under O/W ${\mu}E$ conditions showed that an oil drop size decreased with time due to the solubilization into micelles. On the other hand, both the spontaneous emulsification of water into the oil phase and the expansion of oil drop were observed under W/O ${\mu}E$ conditions because of the diffusion of surfactant and water into the oil phase. Under conditions of a three-phase region including a middle-phase ${\mu}E$, both the rapid solubilization and emulsification of the oil into aqueous solutions were found mainly due to the existence of ultra-low interfacial tension. Dynamic interfacial tension measurements have been found to be in a good agreement with dynamic behavior results.

• Journal of the Korean Chemical Society
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• v.49 no.5
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• pp.435-440
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• 2005

• Clean Technology
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• v.7 no.4
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• pp.291-297
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• 2001

In this study, the stability of concentrated colloidal liquid aphrons (CLAs) containing Aliquat 336 was measured. CLAs in the continuous phase are stabilized by water-soluble surfactant and oil-soluble surfactant. To compare the stability of CLAs, half-life was introduced. According to the change of state of solution, the rate of break-up of concentrated CLAs changed rigorously at critical coagulation concentration. Critical coagulation concentration was measured with changing pH. The effects of ionic strength and concentration of Sodium Dodecyl Benzene Sulfonate (SDBS) on the stability of concentrated CLAs in the continuous phase were also investigated.

• Membrane Journal
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• v.27 no.3
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• pp.255-262
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• 2017

In this study, systematic integration of graphene oxide (GO) into polyacrylonitrile (PAN) nanofibers was accomplished by electrospinning to examine their mechanical properties. Exfoliated GO was initially prepared by the modified Hummer's method, and the surface of the GO was modified with an organic surfactant (e.g., cetyltrimetylammonium chloride) to improve its stability and dispersity. The overall mechanical property of the nanofiber composite membranes was highly improved. Particularly, the composite membranes with the modified GO exhibited much improved mechanical property, presumably due to the increased stability and dispersity of GO during electrospinning.

• Membrane and Water Treatment
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• v.6 no.2
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• pp.141-160
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• 2015

This study aims to investigate the impacts of chemical cleaning on the performance of a reverse osmosis membrane. Chemicals used for simulating membrane cleaning include a surfactant (sodium dodecyl sulfate, SDS), a chelating agent (ethylenediaminetetraacetic acid, EDTA), and two proprietary cleaning formulations namely MC3 and MC11. The impact of sequential exposure to multiple membrane cleaning solutions was also examined. Water permeability and the rejection of boron and sodium were investigated under various water fluxes, temperatures and feedwater pH. Changes in the membrane performance were systematically explained based on the changes in the charge density, hydrophobicity and chemical structure of the membrane surface. The experimental results show that membrane cleaning can significantly alter the hydrophobicity and water permeability of the membrane; however, its impacts on the rejections of boron and sodium are marginal. Although the presence of surfactant or chelating agent may cause decreases in the rejection, solution pH is the key factor responsible for the loss of membrane separation and changes in the surface properties. The impact of solution pH on the water permeability can be reversed by applying a subsequent cleaning with the opposite pH condition. Nevertheless, the impacts of solution pH on boron and sodium rejections are irreversible in most cases.

• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.673-678
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• 1997

Associative acrylic thickeners were prepared by emulsion copolymerization using nonionic vinyl surfactant esters as an associative macromonomer and their rheological properties were investigated. The thickening efficiency was shown to depend on the chain length of therminal hydrophobe and degree of ethoxylation of VSE. increasing the content of VSE enhanced the efficiency of the resulting polymers as a thickener. It was attributed to the intermolecular association of terminal hydrophobes of associative thickener in aqueous solution. The chain transfer agent caused to reduce the molecular weight of associative thickener, resulted in decrease of thickening efficiency.

• Bulletin of the Korean Chemical Society
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• v.29 no.2
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• pp.463-466
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• 2008

We report a method to increase the surface area of the titania films used as the anodes of dye-sensitized solar cells (DSSCs) by applying additional titania-coating. The modification was achieved by spin-coating a coating solution that contained a surfactant with a titania source onto the titania electrodes, followed by calcination. Previous similar attempts without a surfactant all reported decreased surface areas. We fabricated DSSCs by using the modified titania films as the anode and measured their performances. The increased surface area increased the amount of adsorbed dyes, which resulted in increased current densities. At the same time, the titania-coating increased both the open-circuit voltage and the current density by reducing the charge-recombination rates of the injected electrons, similar to the results of literatures. Therefore, our method shows an additional mechanism to increase the current density of DSSCs in addition to the other mechanisms of surface modifications with titania-coatings.