• Bulletin of the Korean Chemical Society
• /
• v.16 no.10
• /
• pp.938-945
• /
• 1995

Hydrolysis of p-nitrophenyl acetate (PNPA) and p-nitrophenyldiphenyl phosphate (PNPDPP) by N-chloro compounds in micellar solution were studied. N,N'-dichloroisocyanuric acid sodium salt (DCI) in cetyltrimethylammonium chloride (CTACl) micellar solution gave pseudo first-order kinetics. But, DCI in cetyltrimethylammonium bromide (CTABr) micellar solution showed typical series first-order kinetics - fast hydrolysis of the esters and concomitant slow decay of the hydrolyzed product, p-nitrophenolate. The hydrolysis rate was decreased as the hydrophobicity of N-chloro compounds was increased, which is the opposite trend to the usual bimolecular micellar reaction. This curious behavior of the N-chloro compounds in the catalytic hydrolysis of PNPA and PNPDPP in a cationic micellar system can be best explained by participation of counter ions of the surfactants during hydrolysis.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2001.09a
• /
• pp.151-154
• /
• 2001

To assess the remediation possibility of groundwater contaminated with MTBE, micellar solubilization by various surfactants was evaluated. Micellar solubilization is basic phenomena to apply micellar enhanced ultrafiltration for groundwater remediation contaminated with MTBE. Sodium dodecyl sulfate (SDS) shows the best removal efficiency among various nonionic, cationic and anionic surfactants. Molar ratio of SDS to MTBE was the most important factor for removal of MTBE using micellar solubilization. With the ratio of more than 13, the removal efficiency was saturated to 55%.

• Journal of the Korean Applied Science and Technology
• /
• v.26 no.3
• /
• pp.370-378
• /
• 2009

Kinetic studies on the ligand substitution reactions of cyanocomplexes were performed in several micellar solutions. It showed the observed rate constants was found to be independent of the entering ligand concentration at high concentration of cyanopyridine and pyrazinecarboxylate. We could see also that in nonionic and anionic micellar solutions no influence of changes in the surfactant concentration on the observed rate constants was found. Taking into account the hydrophilic nature of the cobalt complex, the cobalt complex molecule was expected to be located in the aqueous phase of the micellar systems, where the reaction would take place. In cationic micellar solutions, a small increase in the observed rate constant was found when the cationic surfactant concentration increased. After reaching a maximum, the rate constant decreased on increasing surfactant concentration and subsequently it reached a plateau, where the observed rate constant was independent of changes in the surfactant concentration.

• YAKHAK HOEJI
• /
• v.39 no.5
• /
• pp.495-505
• /
• 1995

The O/W microemulsion systems were made from 2 or 4% (w/w) oil (soybean oil, olive oil or isopropyl myristate) and 10, 15 or 20% (w/w) Brij 96. They were compared with micellar solution of equivalent surfactant concentration m therms of physicochemical properties, and the solubilization of sudan IV. They were characterized by dynamic light scattering, stability, surface tension, viscosity and rheogram. The mean diameters of O/W microemulsion systems were 10-15nm, and those of Brij 96 micellar solutions were 18-19 nm. Both of them were monodisperse systems. The O/W microemulsion systems showed Newtonian flow and their apparent viscosities were lower than those of micellar solutions. The surface tensions of O/W microemulsion systems were increased or decreased depending on the types of oil used, when compared with those of micellar solutions. The O/W microemulsion systems were very stable, and did not show any flocculation or aggregation. Their mean diameters were not changed after three months. But oxidation was observed in microemulsions without nitrogen gas at high temperature. There was a significant improvement in the sudan IV solubffimtion in micromulsion compared with that m the micellar solution containing equivalent concentration of surfactant. The size distribution and mean diameters of O/W micromulsions were not changed when sudan IV was solubilized.

• Journal of the Korean Chemical Society
• /
• v.37 no.6
• /
• pp.562-569
• /
• 1993

The pseudophase separation model is used to describe the effects of pH and n-propanol on the mixed micellar formation of protonated and unprotonated dimethyldodecylamine oxides. Dimethyl-dodecylamine oxide surfactant molecules may exist in aqueous solution in either nonionic (unprotonated) or cationic (protonated) form, and they can be modeled thermodynamically as a binary mixture of cationic and nonionic surfactants. The composition of the binary mixture is varied by adjusting the solution pH. And activities, micellar compositions, and monomeric compositions of two surfactant species can be calculated directly from the experimental titration data by applying pseudophase separation model to the micellar system of DDAO in water/n-propanol. The critical micellar concentrations and the p$K_a$ values of the binary mixture systems are dependent on the micellar composition of the protonated cationic surfactant (X); especially they show the minimum phenomena when they are plotted against the micellar composition of the protonated cationic surfactant (X). The critical micellar concentration of the binary mixed DDAO system is generally decreased when n-propanol is added to the binary mixture system, and the degree of decrease is dependent on the concentration of n-propanol.

• Proceedings of the Korean Society of Applied Pharmacology
• /
• 1996.04a
• /
• pp.284-284
• /
• 1996

Titrated Extract of Centella asiatica (TECA) is a poorly water-soluble extract from the Centella asiatica. Despite excellent wound preparation causes pain due to a low aqueous solubility and high hypertonicity and therefore, the patient's compliance of this drug is low. The objective of this study is to design a formulation of TECA with an improved therapeutic applicability via an adequate solubilization. A mixture of propylene glycol and ethoxylated hydrogenated caster oil achieved an acceptable solubilization of TECA (i.e. 10%) via a formulation of micelle. A preparation of extemporaneous TECA micelle was achieved by a dilution of the original micellar formulation with either water or saline. An estimated distribution of particle size was between 15.9 and 32.6 ㎜. The osmotic pressure of the formulation was found to be much lower than that found In a commercially available injectable (i.e. Madecassole). The erthrocytic hemolysis of micellar solution was lower than that with the conventional dosage form, consistent with the osmotic pressure data. Pain score after an injection of the micellar solution was assessed by the hind-paw writhing test using ICR mice and compared with that found with the conventional injectable. The data indicated that the injection of the micellar solution was a significantly less painful. These results indicated that a micellar solubilization, followed by an extemporaneous dilution, is a novel formulation of TECA with an improved therapeutic applicability.

• Archives of Pharmacal Research
• /
• v.28 no.3
• /
• pp.370-375
• /
• 2005

The objective of this study was to develop a new reverse micelle-based microencapsulation technique to load tetracycline hydrochloride into PLGA microspheres. To do so, a reverse micellar system was formulated to dissolve tetracycline hydrochloride and water in ethyl formate with the aid of cetyltrimethylammonium bromide. The resultant micellar solution was used to dissolve 0.3 to 0.75 g of PLGA, and microspheres were prepared following a modified solvent quenching technique. As a control experiment, the drug was encapsulated into PLGA microspheres via a conventional methylene chloride-based emulsion procedure. The micro­spheres were then characterized with regard to drug loading efficiency, their size distribution and morphology. The reverse micellar procedure led to the formation of free-flowing, spherical microspheres with the size mode of 88 ~m. When PLGA microspheres were prepared follow­ing the conventional methylene chloride-based procedure, most of tetracycline hydrochloride leached to the aqueous external phase: A maximal loading efficiency observed our experimental conditions was below $5\%$. Their surfaces had numerous pores, while their internal architecture was honey-combed. In sharp contrast, the new reverse micellar encapsulation technique permitted the attainment of a maximal loading efficiency of 63.19 $\pm$$0.64\%$. Also, the microspheres had smooth and pore-free surfaces, and hollow cavities were absent from their internal matrices. The results of this study demonstrated that PLGA microspheres could be successfully prepared following the new reverse micellar encapsulation technique.

• Korea-Australia Rheology Journal
• /
• v.14 no.3
• /
• pp.129-138
• /
• 2002

A cationic surfactant, cetyltrimethylammonium $\rho$-toluenesufonate (CTA$\rho$TS), forms long threadlike micelles in aqueous solution. The threadlike micelles make concentrated entanglement networks, so that the solution shows pronounced viscoelastic behavior as concentrated polymer systems do. However, a mechanism for a process responsible for the longest relaxation time of the threadlike micellar system is different from that of semi-dilute to concentrated polymer systems. The threadlike micellar system exhibits unique viscoelasticity described by a Maxwell model. The longest relaxation time of the threadlike micellar system is not a function of the concentration of CTA$\rho$TS, but changes with that of $\rho$-toluenesufonate ($\rho$$TS^{-}$) ions in the bulk aqueous phase supplied by adding sodium $\rho$-toluenesulfonate (NapTS). The rates of molecular motions in the threadlike micelles are not influenced by the concentration of $\rho$$TS^{-}$ anions, therefore, molecular motions in the threadlike micelles (micro-dynamics) are independent of the longest relaxation mechanism (macro-dynamics). A nonionic surfactant, oleyldimethylamineoxide (ODAO), forms long threadlike micelles in aqueous solution without any additives. The aqueous threadlike micellar system of ODAO also shows Maxwell type viscoelastic behavior. However, the relaxation mechanism for the longest relaxation process in the system should be different from that in the threadlike micellar systems of CTA$\rho$TS, since the system of ODAO does not contain additive anions. Because increase in the average degree of protonation of head groups of ODAO molecules in micelles due to adding hydrogen bromide causes the relaxation time remarkably longer, changes in micro-structure and micro-dynamics in the threadlike micelle are closely related to macro-dynamics in contrast with the threadlike micellar system of CTA$\rho$TS.

• Analytical Science and Technology
• /
• v.10 no.5
• /
• pp.325-331
• /
• 1997

Among various CE separation methods, micellar electrokinetic capillary chromatography(MECC) method using sodium dodecylsulfate(SDS) provides rapid and accurate separation of organic explosive constituents with easy. The running buffer was composed with 2.5 mM borate and 25mM SDS(pH 8.5). Addition of 1M urea and 10% organic modifiers (acetonitrile, methanol and ethanol) improves the resolution of adjacent explosive constituents. When 15 explosive constituents were developed in MECC, most constituents were separated successively while RDX/TNB and DNN/DEP were not, and detection limits of separated compounds are in range of 1 to 4 ppm.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2003.09a
• /
• pp.413-416
• /
• 2003

Micellar enhanced ultrafiltration(MEUF) is a surfactant-based separtaion technique which can remove dissolved organics or multivalent ions from water. In this study, trichloroethylene(TCE) and chromate were simultaneouly removed using MEUF and cetyltrimethylammoniun chloride (CPC) was used as a surfactant. The removal efficiency of chromate was 99% and that of TCE was more than 80%. The presence of TCE or chromate did not affect removal efficiency of each pollutants because the predominat mechanism of TCE and chromate are different.