• Bulletin of the Korean Chemical Society
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• 제29권8호
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• pp.1485-1490
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• 2008

Dumbbell-shaped aromatic amphiphilic molecules consisting of a dodeca-p-phenylene as a rigid segment and oligoether dendrons as a flexible chains were synthesized, characterized, and their aggregation behavior was investigated in the bulk and at the air-water interface. In contrast to the molecule 2 which shows a nematic liquid crystalline state, molecule 1 based on shorter dendritic chains was observed to self-assemble into a 3-D primitive orthorhombic supercrystal. And molecule 1 at the air-water interface was observed to reorganize from circular plates to ring structures by lateral compressions.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2012년도 춘계학술논문집 1부
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• pp.177-181
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• 2012

Association is an important contribution to the overall hydrogen bonding in surfactant systems, especially in systems of colloidal and biological interest. Amphiphile systems, especially micelle and microemulsion systems, showed highly non-ideal behavior due to the intermolecular association and intramolecular association. The objective of this research is to present a lattice fluid equation of state that combines the quasi-chemical nonrandom lattice fluid model with modified Veytsman statistics for intra + inter molecular association to calculate phase behavior for mixture containing surfactant systems. The present EOS could correlate the literature data well for mixtures containing nonionic surfactant systems.

• Korea-Australia Rheology Journal
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• 제11권4호
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• pp.321-328
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• 1999

This paper discusses the rheology of complex interfaces comprised of amphiphilic materials that are susceptible to flow-induced orientation and deformation. The consequence of the coupling of the film micro-structure to flow leads to nonlinear rheology and surface fluid dynamics. Experimental methods designed to determine the mechanical rheological material functions of fluid-fluid interfaces as well as local, molecular and morphological responses are presented. These include a newly developed interfacial stress rheometer, flow ultraviolet dichroism, and Brewster-angle microscopy. These techniques are applied to a number of complex interfaces ranging from low molecular weight amphiphiles to polymer monolayers. Nonlinear flow phenomena ranging from two-dimensional nematic responses to highly elastic surface flows that manifest surface normal stress differences and elongational viscosities are described.

• Bulletin of the Korean Chemical Society
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• 제31권12호
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• pp.3735-3739
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• 2010

Branched oligopeptides prepared by coupling a very hydrophobic aspartic diamino acid ethyl ester such as Asp $(LeuEt)_2$, $Asp(IleEt)_2$ and $Asp(PheEt)_2$ to glycine or glycylphenylalanine were grafted to the cyclotriphosphazene backbone bearing an equimolar hydrophilic poly(ethylene glycol) (PEG). The properties of the resultant amphiphiles were examined in comparison with those of the linear oligopeptide analogues previously reported. All cyclic phosphazene trimers grafted with the branched tetra- and pentapeptides displayed a normal trend of thermosensitivity depending on their hydrophilic to hydrophobic balance, but the stability and particle size of their micelles were found to be greatly dependent on the fine structure of the branched oligopeptides grafted. The trimers bearing branched tetrapeptides with a low hydrophobicity were found to form unstable micelles initially, which reassemble into thermodynamically more stable polymersomes.

• 멤브레인
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• 제2권2호
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• pp.112-121
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• 1992

최근 십여년동안 자원, 에너지, 환경의 모든 면에서 기능성막의 역할이 증대해짐에 따라 기능성막에 대해 큰 관심이 모아지고 있다. 기존하는 기능성막의 소재면에서 볼 때 고분자막(고체막), 액체막으로 대별할 수 있으며, 이들의 경우 해수의 담수화, 원료 및 제품의 분리, 농축, 정제, 회수공정 또한 석유화학분야에서 고효율$\cdot$고선택성 기체혼합물 분리, 산업용 폐수처리분야 뿐 만 아니라, 태양에너지의 효과적인 이용, 전도성, 감광성, 광학특성막 등을 이용한 각종 센서제조 등 실로 광범위한 분야에서 응용되어지고 있다. 기능성막의 관점에서 볼 때, 고기능$\cdot$고효율$\cdot$고선택성을 가지는 막은 생태계에 존재하는 생체막이 가장 이상적이라 할 수 있다.

• Bulletin of the Korean Chemical Society
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• 제19권6호
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• pp.645-649
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• 1998

In order to develop pH-sensitive liposomes that are stable in plasma, liposomes containing membrane-spanning bipolar amphiphiles as protonatable components were studied. Sonicated small unilamellar liposomes composed of dioleoylphosphatidylethanol amine (DOPE), dioleoylphosphatidylcholine (DOPC) and bis(6-hemisuccinyloxyhexyl) fumarate (BHF) in a 3 : 1 : 1 molar ratio are stable at neutral pH, but destabilized at weakly acidic pH with 50% leakage of entrapped materials at about pH 5.5. The liposomes are relatively stable in plasma such that only a few percent entrapped calcein was released in 50% plasma within 1.5 h incubation at 37 ℃, while about 10% entrapped calcein was released from sonicated liposomes composed of DOPE, DOPC, and oleic acid (OA) in a 3 : 1 : 1 molar ratio under the identical conditions. The aqueous contents mixing and lipid components mixing experiments suggest that the protonation of BHF may induce fusion between the liposomes, followed by the release of the entrapped materials.

• Bulletin of the Korean Chemical Society
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• 제18권2호
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• pp.190-193
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• 1997

In search of new amphiphiles that form coordinatively polymerized bilayer membranes (CPBMs) in water, N-dodecyl-3-[2-hydroxy-3-(4-carboxymethyl-2-thiazolylazo)-5-methylphenyl]propanamide (5) was prepared. The bilayer membranes of 5 prepared in the presence of 2 equivalents of NaOH were further sonicated in the presence of transition metal ions such as Ni(Ⅱ), Cu(Ⅱ), Co(Ⅱ), or Co(Ⅲ) at > 80 ℃ to obtain CPBMs. The CPBMs of 5 were characterized by transmission electron microscopy, gel filtration, resistivity against disruption in aqueous ethanol, visible spectra, and release of entrapped 5(6)-carboxyfluorescein. Remarkable stabilization of the bilayer membranes through coordinative polymerization was evidenced by the resistivity of the Ni(Ⅱ)-CPBM of 5 against disruption in 40%(v/v) ethanol upon incubation for 20 hr.

• Bulletin of the Korean Chemical Society
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• 제12권2호
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• pp.170-177
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• 1991

A lattice mean field theory is developed to investigate the conformational properties of monolayer amphiphiles at the air-water interface. By generalizing Dill and Cantor's method and by extending Whittington's recurrence equation, we derive the supermatrix recurrence equation which is applied to calculation of various segment density profiles and order parameter, etc. In deriving the equation, we incorporated the chain stiffness effect and the chain connectivity which are distinguished features of linear chain molecule. Our result shows that, as the surface coverage $\sigma$ increases the chain ordering process with respect to vertical axis of the lattice system becomes dominant.

• Bulletin of the Korean Chemical Society
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• 제31권5호
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• pp.1262-1266
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• 2010

In this study, we investigated the use of liquid crystals to selectively detect the activity of enzymes at interfaces decorated with oligopeptide-based membranes. We prepared a mixed monolayer of tetra(ethylene glycol)-terminated lipids and carboxylic acid-terminated lipids at the aqueous-liquid crystal (LC) interface. The 17 amino-acid oligopeptide SNFKTIYDEANQFATYK was then immobilized onto this mixed monolayer through N-hydroxysuccinimide-activation of the carboxylic acid groups. We examined the orientational behavior of nematic 4-cyano-4'-pentylbiphenyl (5CB) after conjugation of the 17 amino-acid oligopeptide with the mixed monolayer assembled at the interface. Immobilization of the oligopeptide caused orientational transitions in 5CB, with a change from homeotropic (perpendicular) to tilted alignment, which was primarily due to the reorganization of the monolayer. The orientation of the 5CB molecules returned to its homeotropic state after contacting the interface containing ${\alpha}$-chymotrypsin, which can cleave the immobilized oligopeptide. Control experiments confirmed that the enzymatic activity of ${\alpha}$-chymotrypsin triggered the ordering transitions in the LC. These results suggest that the LC can provide a facile method for selective detection of enzymatic activity.

• 한국식품조리과학회지
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• 제13권2호
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• pp.185-191
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• 1997

The effects of five hydrated emulsifiers with or without specified proteins (flour, egg) and/or polydextrose on the reduced-calorie cake as baked product model systems were compared. The small molecule amphiphiles (SMA) used were monoglycerides (MG), sorbitan monostearate (SMS), polysorbate (PS) 60, sucrose ester (SE) F7O, and SE Fl60. All flour batters with each emulsifier and supplements had similar low foam drainages (0.00∼1.03$m\ell$) indicating those systems were fairly stable in the presence of flour protein. The cake batter using starch instead of flour without egg and polydextrose and with some emulsifiers had relatively large amount of drainages (4.20∼5.87$m\ell$). When the egg and polydextrose were added to the blank cake batters using starch, foam drainages tended to show relatively low scores (0.13∼1.48$m\ell$) indicating the cake batter dispersion system is stabilized. Starch cakes made with SE F70 without egg or polydextrose(blank) unexpectedly had high volume index of 199.