• Applied Chemistry for Engineering
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• v.34 no.5
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• pp.488-492
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• 2023

In this study, a carbon film derived from a polymer/lignin composite precursor was produced by a carbonization cycle with a controlled temperature profile. The feasibility of successful formation of the carbon film using the carbonization cycle was monitored. The adsorption behavior of the carbon film toward various molecules, such as nonpolar and polar organic molecules, and dyes was investigated using ultraviolet/visible (UV/Vis) spectroscopy compared with that of carbonized lignin. Cyclic voltammetry (CV) analysis proved that a robust carbon film was prepared by the carbonization cycle. It was also demonstrated that the carbonized lignin and carbon film showed adsorption capability toward all types of organic molecules, in particular organic dyes, owing to the carbonized lignin. This work provides important information for future relevant research.

• KSBB Journal
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• v.13 no.1
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• pp.96-100
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• 1998

Two promoters (trc and P$\rho$) were inserted in PHA operon derived from Alcaligenes eutrophus to obtain high chain molecules of polyhydroxybutyrate (PHB) in recombinant Escherichia coli. Newly designed PHA operon was used to control the gene expressions of hydroxybutyric CoA and PHA polymerization, separately. Plasmids containing new synthetic operon was transformed into E. coli DH5$\alpha$ and analyzed for PHB production. Without induction of the PHA biosynthetic operon, PHA synthase which has low activity might supply low concentration of initiator during the polymerization reaction, resulting very high molecular weight of polymer. An increase of PHB average molecular weight was observed with decreased IPTG (isopropyl $\beta$ -Dithiogalactosidase) concentration. When no IPTG was added to the culture of E. coli DH5$\alpha$ /$\rho$ SJS1 which contained two promoters in PHA operon, high chain polymer having an average molecular weight of $2.5{\times}10^7$ was achieved. Analysis of the enzyme activities of PHA biosynthetic enzymes suggests that PHA synthase, the enzyme responsible for polymerizing 3-hydroxybutyric CoA, controls the molecular weight of PHB produced in vivo.

• Membrane Journal
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• v.5 no.2
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• pp.89-96
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• 1995

The monolayer characteristics of phosphate amphiphiles with azobenzene at air/water interface were studied by the measurment of $\pi-A$ curves and absorption spectra. Immediately after being spread on the water surface, these amphiphiles having strong intermolecular hydrogen bonding interactions showed the typical absorption spectra which resulted from domain formation. But the aggregated domains could be controlled by changing the subphase conditions (adding bulky salt and rasing pH). Addition of metal ions in subphase changes the molecular orientation of monolayer. As the metal ion charge increases ($1\leq2$ < 3 < 4 valence), the absorption maximum (310nm) of the amphiphile with azobenzene shifts to a longer wavelength (350nm) which means that the orientation of the amphiphile is tilted. These results suggest that the molecular orientation, and furthermore the aggregation state of monolayer can be possibly controlled by the interaction of metal ions with different charge types.

• Composites Research
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• v.30 no.2
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• pp.102-107
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• 2017

The preceramic polymer can realize a variety of complex ceramic structures that can not be obtained by conventional ceramic processes. Polycarbosilane, which is a typical preceramic polymer, can control the molecular structure, molecular weight and molecular weight distribution for preparing complex morphology and microstructure of SiC ceramics, including SiC fiber. In this paper, synthesis and molecular structure control technique of polycarbosilane is explained. The silicon carbide fiber prepared by melt spinning, stabilization and heat treatment, and ceramic fiber composites technology made by PIP process are also discussed. In addition, we introduce an example of the development of a complex silicon carbide material such as a silicon carbide hollow fiber having a nanoporous structure.

• Polymer(Korea)
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• v.27 no.5
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• pp.493-501
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• 2003

Poly(methyl methacrylate) (PMMA) particles, denture base resin, were synthesized by suspension polymerization through control of polymerization conditions (stabilizer concentration, co-monomer concentration, and the agitation speed) and evaluated changes in molecular weight and particle size. We also investigated their mechanical properties of compression-molded samples which were from synthesized polymer powder mixed with methyl methacrylate (MMA) solution. under the condition of volumetric ratio as 2:1(PMMA powder and MMA solution). The results shows that the mechanical properties were mainly affected by particle size over 100 ${\mu}$m (in particle size) and by molecular weight under 100 ${\mu}$m (in particle size). From these results, we concluded that the most appropriate particle size of PMMA powder for heat-cured denture base resins is around 100 ${\mu}$m. and its molecular weight is around 300000 (M$\sub$n/).

• Proceedings of the Korean Fiber Society Conference
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• 2002.04a
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• pp.433-436
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• 2002

형상기억재료는 형상기억효과, 회복변형효과, 형상고청효과, 진동제어효과 등의 특성으로 인하여 중요한 지능재료(smart materials)의 하나로 기대되고 있다. 형상기억 재료로는 합금, 세라믹, 고분자, 겔 등을 들 수 있지만 Ti-Ni 합금(Nitinol)이 가장 많이 이용되고 있다. 그러나 형상기억고분자는 형상기억합금에 비하여 가볍고 형상회복률이 높으며 가공이 쉽고 투명할 뿐만 아니라 염색이 가능하기 때문에 물성과 경제적인 면에서 유리하다. (중략)

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.21-21
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• 2010

본 개발에서는 초고속 복합 분자펌프 구동을 위한 디지털 구동장치를 설계하였다. BLDC구동을 위한 디지털 제어 시스템의 핵심제어 보드 설계 및 모듈 설계를 하여 보드제작 및 기본성능평가를 하고 고속 회전 실험을 하였다. AMB의 구동 특성을 파악하였으며 AMB 구동을 위한 와전류식 변위 센서의 구동 특성을 파악하였다. 와전류식 변위 센서의 거리측정 방법을 구현하였으며 AMB와 와전류식 변위센서 구동부를 설계하였다.

• Elastomers and Composites
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• v.47 no.1
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• pp.30-35
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• 2012

Novel bio-polybutadiene polymers with controlled molecular weight (MW), MW distribution, chemical composition and micro structure were synthesized by a living anionic polymerization of butadiene and the subsequent coupling reaction of the thus obtained living polybutadiene and a vegetable oil. Anionic polymerization of butadiene was carried out in THF solvent using n-BuLi initiator. The resulting living polybutadienyllithium polymer was then reacted with epoxidized soybean oil (ESO) to obtain a star-polymer of polybutadiene and vegitable oil. Three different bio-elastomers were prepared by coupling living polybutadienes of MWs 1000, 5000 and 1000g/mol with ESO. The molecular structure and MW of the polybutadienes and bioelastomers were characterized by $^1H$-NMR, FTIR and GPC techniques.

• Journal of Energy Engineering
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• v.18 no.2
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• pp.125-131
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• 2009

Physical characteristics of metals such as hardness, wear-resistance and corrosion-resistance can be artificially controlled by ion implantation. The interaction between ion and solid surface was modeled in molecular scale and simulated by the molecular dynamics method in order to understand the ion implantation mechanism. From the microscopic point of view, the molecular behaviors were observed for improving characteristics of ion implantation. For these purposes, the implantation mechanism and the influences of incident energy, surface temperature and molecular weight were discussed in this study. As the results, the penetration probability was even decreased if incident energy was exceeded any values in the case of high temperature of solid surface. Moreover, it was confirmed that ion implantation into solid surface with amorphous state could be more effective for some conditions.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.5
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• pp.160-168
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• 2010

This paper tried to find out NO generation and removal mechanisms in the space of the atmospheric pulsed barrier discharge using laser induced fluorescence method, which is a very effective approach to the measurement of spatio-temporal density of specific molecules. The propagation velocity of the primary streamer reaches about $2.7{\times}10^6$[m/s] and the secondary streamer is produced in the vicinity of positive electrode after the primary streamer finished. In this work, pulse Nd:Yag and Dye lasers are used for generating the specific wavelength of 226[nm], which is possible to excite NO molecules into $A^2{\Sigma}^+{\rightarrow}X^2{\prod}$(0,0) and fluorescence signals as the transition of $A^2{\Sigma}^+{\leftarrow}X^2$(0,2) is measured. For the effective removal of NO molecules in the plasma discharge process, the lower oxygen contents are needed and the influence of secondary streamer for the reduction mechanism of NO molecules is important