• Proceedings of the KIEE Conference
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• 2004.11a
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• pp.209-211
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• 2004

In the Langmuir-Boldgett(LB) technique, a monolayer on the water surface is transferred on to a substrate, which is raised and dipped through the surface, and one can obtain multilayers in which constituent molecules periodically are arranged in layer. The LB technique has attracted considerable interest in the fabrication of electrical and electronic device, e.g.. Many researchers have investigated the electrical properties of monolayer and multiplayer films. Dendrimers represent a new class of synthetic macromolecules sharacterized by a regularly branched treelike structure. Multiple branching yields a large number of chain ends, which distinguishes dendrimers from conventional starlike polymers and microgels. Azobenzene dendrimer is one of the dendritic macromolecules that includes the azo-group which exhibits a photochromic character. Due to the presence of the charge transfer part, the azo-group, and having a rod-shaped structure, these compounds are expected to have the potential interest in electronics and ptoelectronics, especially in nonlinear optics. In the present paper, we give a pressure stimulation into organic thin films and detect the induced displacement current.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.489-490
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• 2006

Branched sulfonated poly(ether sulfone-ketone) copolymer was prepared with bisphenol A, 4,4-difluorobenzophenone, sulfonated chlorophenyl sulfone (40mole% of bisphenol A) and THPE (1,1,1-tris-p-hydroxyphenylethane). THPE was used 0.4 mol% of bisphenol A to synthesize branched copolymers. Organic-inorganic nano composite membranes were prepared with copolymer and a series of $SiO_2$ nanoparticles (20 nm, 4, 7 and 10 wt%). The composite membranes were cast from dimethylsulfoxide solutions. The films were converted from the salt to acid forms with dilute hydrochloric acid. The membranes were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol. Branched copolymer and nano composite membranes exhibit proton conductivities from $1.12{\times}10^{-3}$ to $6.04{\times}10^{-3}\;S/cm^2$, water uptake from 52.9 to 62.4%, IEC from 0.81 to 1.21 meq/g and methanol diffusion coefficients from $1.2{\times}10^{-7}$ to $1.5{\times}10^{-7}\;cm^2/S$.

• Textile Coloration and Finishing
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• v.4 no.4
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• pp.81-89
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• 1992

Graft polymers of alginic acid-PMMA, different in composition and Mv of branched PMMA, were prepared by emulsion graft polymerization at various MMA concentrations. In aqueous dispersion solution, the adsorption of graft polymer on the montmorillonite was carried out to modify the surface property of powder, and the adsorption of PMMA in organic solvents (acetone, benzene) on the modified surface of powder were observed. The results obtained were as follows. 1. In emulsion graft polymerization of MMA on the sodium alginate in aqueous solution, SA conversion, MMA conversion and % grafting were increased with increasing MMA concentration where as graft efficiency was decreased. 2. The adsorption amount of graft polymer was increased with the elevation of temperature and the increased of dispersion concentration and with the increase of branched PMMA composition of graft polymer. 3. In organic solvent, the adsorption of PMMA on the surface modified particle was proceeded by the orientation along the stretched branched PMMA of adsorbed graft polymer which is in radial direction to the particle surface. 4. The adsorbed amount of PMMA was increased as the temperature and concentration of PMMA solution, the branching of adsorbed graft polymer and the solvency of solvent were increased.

• Macromolecular Research
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• v.15 no.3
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• pp.238-243
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• 2007

Nanofibers were prepared by electrospinning a solution of poly(lactic-co-glycolic acid) (PLGA) and their mean diameter was 340 nm. The PLGA nanofibers were treated with a plasma in the presence of either oxygen or ammonia gas to change their surface characteristics. The hydrophilicity of the electrospun PLGA nanofibers was significantly increased by the gas plasma treatment, as confirmed by contact angle measurements. XPS analysis demonstrated that the chemical composition of the PLGA nanofiber surface was influenced by the plasma treatment, resulting in an increase in the number of polar groups, which contributed to the enhanced surface hydrophilicity. The degradation behavior of the PLGA nanofibers was accelerated by the plasma treatment, and the adhesion and proliferation of mouse fibroblasts on the plasma-treated nanofibers were significantly enhanced. This approach to controlling the surface characteristics of nanofibers prepared from biocompatible polymers could be useful in the development of novel polymeric scaffolds for tissue engineering.

• Journal of Electrochemical Science and Technology
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• v.14 no.4
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• pp.303-310
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• 2023

Microbial fuel cells (MFCs) are a bioelectrochemical system where electrochemically active bacteria convert organic waste into electricity. Poly(vinyl alcohol) (PVA) and chitosan (CS) are polymers that have been studied as potential alternative ion exchange membranes to Nafion for many electrochemical systems. This study examined the optimal mixing ratio of PVA and chitosan CS in a PVA:CS composite membrane for MFC applications. PVA:CS composite membranes with 1:1, 2:1, and 3:1 ratios were synthesized and tested. The water uptake and ion exchange capacity, Fourier transform infrared spectra, and scanning electron microscopy images were analyzed to determine the physicochemical properties of PVA:CS membranes. The prepared membranes were applied to the ion exchange membrane of the MFC system, and their effects on the electrochemical performance were evaluated. These results showed that the composite membrane with a 3:1 (PVA:CS) ratio showed comparable performance to the commercialized Nafion membrane and produced more electricity than the other synthesized membranes. The PVA:CS membrane implemented MFCs produced a maximum power density of 0.026 mW cm^-2 from organic waste with stable performance. Therefore, it can be applied to a cost-effective MFC system.

• ETRI Journal
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• v.27 no.5
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• pp.585-594
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• 2005

A small electronic nose (E-Nose) system has been developed using an 8-channel vapor detection array and personal digital assistant (PDA). The sensor array chip, integrated on a single microheater-embedded polyimide substrate, was made of carbon black-polymer composites with different kinds of polymers and plasticizers. We have successfully classified various volatile organic compounds such as methanol, ethanol, i-propanol, benzene, toluene, n-hexane, n-heptane, and c-hexane with the aid of the sensor array chip, and have evaluated the resolution factors among them, quantitatively. To achieve a PDA-based E-Nose system, we have also elaborated small sensor-interrogating circuits, simple vapor delivery components, and data acquisition and processing programs. As preliminary results show, the miniaturized E-Nose system has demonstrated the identification of essential oils extracted from mint, lavender, and eucalyptus plants.

• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.72-74
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• 2003

There has been extensive interest in the development of new nanocomposites. One kind of these systems is the hybrid based on organic polymers and inorganic minerals consisting of layered silicates. Some properties like stiffness, strength, barrier properties, thermal, and oxidative stability can be improved by the presence of the filler in the polymeric matrix[1]. It is reported that, in the nylon 6/clay nanocomposites, the modulus is increased, but impact strength and elongation at break are drastically decreased. (omitted)

• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.40-43
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• 2003

최근 관심의 대상이 되고 있는 유기박막트랜지스터 (Organic Thin Film Transisto., OTFT)는 현재 사용되고 있는 무기물 트랜지스터에 비해 가볍고 낮은 공정 온도와 가격으로 인하여 대면적 LCD, EL, smart card의 능동구동소자로서 적용이 가능하다고 알려져 있다[1,2]. 하지만 현재 연구되고 있는 단분자 유기물을 사용한 OTFT는 비교적 높은 온도에서 소자의 각 구성요소를 증착해야 되므로 여전히 복잡한 공정이 필요하며, 활성층으로 쓰이는 유기물과 금속전극의 계면문제로 전기적 특성이 떨어진다[3]. (중략)

• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1703-1707
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• 2013

A fast and simple sampling and sample preparation device, (NTD) has been developed and applied to sample and analyze volatile components from ground coffee beans. Coffee fragrances and other volatile organic compounds (VOCs) were sampled by the NTD and then analyzed by gas chromatograph-mass spectrometry (GC/MS). Divinylbenzene (DVB) particles (80/100 mesh size) were the sorbent bed of the NTD. More than 150 volatile components were first identified based on the database of the mass library and then finally 30 fragrances including caffeine were further confirmed by comparing experimental retention indices (i.e. Kovat index) with literature retention indices. Total sampling time was 10 minutes and no extra solvent extraction and/or reconstitution step need. Straight n-alkanes (C6-C20) were used as retention index probes for the calculation of experimental retention indices. In addition, this report suggests that an empty needle can be an alternative platform for analyzing polymers by pyrolysis-GC/MS.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.541-545
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• 2000

For the sustained release formulation of recombinant human growth hormone (rhGH), dissociable rhGH aggregates were microencapsulated within poly(D,L-lactic-co-glycolic acid) [PLGA] microparticles. rhGH aggregates with 2 - 3 m Particle diameter were first produced by adding a small volume of aqueous rhGH solution into a partially water miscible organic solvent phase(ethyl acetate) containing PLGA. These rhGH aggregates were then microencapsulated within PLGA polymer phase by extracting ethyl acetate into an aqueous phase pre-saturated with ethyl acetate. The resultant microparticles were 2 - 3 m in diameter similar to the size of rhGH aggregates, suggesting that PLGA polymer was coated around the protein aggregates. Release profiles of rhGH from these microparticles were greatly affected by changing the volume of the incubation medium. The release rhGH species consisted of mostly monomeric form with having a correct conformation. This study reveals that sustained rhGH release could be achieved by microencapsulating reversibly dissociable protein aggregates within biodegradable polymers.