• Journal of Life Science
• /
• v.19 no.4
• /
• pp.457-461
• /
• 2009

We optimized dextranase culture conditions by batch fermentation using Lipomyces starkeyi KCTC 17343. Furthermore, dextranase was purified by an ultra-membrane, and then dextran hydrolyzates were characterized. Cell growth and dextranase production varied depending on the initial culture pH and temperature. The conditions of optimal dextranase production were met in a pH range of 4-5 and temperature between $25-30^{\circ}C$. At optimal fermentation conditions, total enzyme activity and specific enzyme activity were about 4.85 IU/ml and 0.79 IU/g cells, respectively. The specific growth rate was examined to be $0.076\;hr^{-1}$. The production of dextranase in culture broth was very stably maintained after mid-log phase of growth. The enzyme hydrolyzed dextran into DP (degree of polymerization) 2 to 8 oligodextran series. Analysis of the composition of hydrolysates suggested that the enzyme produced is an endo-dextranase.

• Applied Chemistry for Engineering
• /
• v.10 no.1
• /
• pp.148-153
• /
• 1999

In situ composites containing a thermotropic liquid crystalline polymer were prepared by polycondensation of 1,4-bis(p-hydroxy-benzoyloxy)butane with 2-bromoterephthaloyl chloride in a poly(methyl methacrylate) solution. Morphology and mechanical, thermal properties of the composites were examined by differential scanning calorimeter(DSC), dynamic mechanical thermal analyser(DMTA), optical microscope and scanning electron microscope(SEM). The TLCP domains showed nematic phase. The glass transition temperature($T_g$) and mechanical properties of the PMMA in the composites increased with increasing the content of TLCP. The TLCP domains were finely dispersed in the PMMA matrix. The 20 wt % TLCP/PMMA composite prepared by in situ polymerization showed more improved mechanical property with finely well dispersed morphology compared with that prepared by solution blending of the same composition.

• Applied Chemistry for Engineering
• /
• v.7 no.5
• /
• pp.843-848
• /
• 1996

Porous resin beads of Poly(styrene-co-divinylbenzene) have been prepared by suspension polymerization. The bead could be made porous in the region above 30wt% of the crosslinking agent(divinylbenzene ) and the porogenic agent(toluene), respectively. The specific surface area of porous beads increased with increasing the concentrations of divinylbenzene and toluene. The specific surface area of the porous resin bead decreased, when sulfonated with concentrated sulfuric acid. The catalytic activity of sulfonated resin catalyses increased with increasing the degree of crosslinking in the liquid-phase reesterification of ethyl acetate with 1-propanol. The adsorbed quantity of sodium dodecylbenzene sulfonate in an aqueous solution also increased with increasing surface area of porous resins.

• Polymer(Korea)
• /
• v.31 no.4
• /
• pp.289-296
• /
• 2007

The material factors influencing the sound absorption of the polyurethane foam were investigated with FT-IR, small-angle X-ray scattering (SAXS), and dynamic mechanical thermal analyzer (DMTA). The measurements were performed using the samples which had a similar cell structure but different absorption coefficients. It was found that the ability of the sound absorption of the polyurethane foams was closely related to the damping behavior over the transition range. In order to confirm the use of the low monol polyol (LMP) in high-performance applications, the polyurethanes based on LMP and polypropylene oxide polyol (PPG) were prepared by the solution polymerization method. The microstructure and the physical properties of these polyurethanes were compared. The PPG-based polyurethane showed a higher level of the phase-separated structure because the considerable amount of monol presented in PPG made a contribution to the increased chain mobility. However the short chains formed due to the monol species deteriorated the damping property. As a result, the LMP-based polyurethane showed the superior damping behavior as compared with the PPG-based one.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
• /
• 2001.06a
• /
• pp.1158-1158
• /
• 2001

Fast and dynamic biochemical, enzymatic and morphological changes occur during the so-called generative development and during the vegetative processes in seeds. The most characteristic biochemical and compositional changes of this period are the formation and decline of storage components or their precursors, the change of their degree in polymerization and an extensive change in water content. The aim of the present study was to detect the maturation processes in seed nondestructively and to verify the applicability of near infrared spectroscopic methods in the measurement of physiological, chemical and biochemical changes in wheat seed. The amount and variation of different water “species” has been changed intensively during maturation. Characteristic changes of three water absorption bands (1920, 1420 and 1150 nm) during maturation were analysed. It was concluded that the free/bound transition of water molecules could be followed sensitively in different region of NIR spectra. Kinetic changes of carbohydrate reserves were characteristic during maturation. An intensive formation and decline of carbohydrate reserves were observed during early stage of maturation (0 -13 days, high energy demand). An accelerated formation of storage carbohydrates (starch) was detected in the second phase of maturation. Five characteristic absorption bands were analysed which were sensitive indicators the changes of carbohydrates occurred during maturation. Precursors of protein synthesis and the synthesis of reserve proteins and their kinetic changes during maturation were followed from NIR spectra qualitative and qualitatively. Dynamic formation of amino acids and the changes of N forms were detected by spectroscopic, chromatographic and by capillary electrophoresis methods. Calibration equations were developed and validated in order to measure the optimal maturation time protein and moisture content of developing wheat seeds. The spectroscopic methods are offering chance and measurement potential in order to detect fine details of physiological processes. The spectra have many hidden details, which can help to understand the biochemical background of processes.

• Journal of the Korean Ceramic Society
• /
• v.41 no.2
• /
• pp.151-157
• /
• 2004

Because of the excellent thermal and chemical properties of mullite and cordierite as the stable oxide ceramic materials, they were widely used from engineering materials to electronic materials. Notwithstanding of their high demands, mullite was synthesised because it is not existed in nature. It is also difficult to produce cordierite of fine powder with high purity due to the narrow range of synthetic temperature. Mullite was synthesised by solid state reaction. However, synthesized mullite has been inhomogeneous. Because of the facts, various synthetic methods have been studied so far including sol-gel method. The purpose of this study is to synthesis mullite and cordierite of fine powder with high purity at the lower temperature by solution-polymerization route using PVA as a polymer carrier, which is an economical method by using low cost materials. As a result, mullite and cordierite were produced with mono crystal phase at 1200$^{\circ}C$ and 1250$^{\circ}C$, respectively, and their surface area over 20 ㎡/g.

• Applied Chemistry for Engineering
• /
• v.8 no.1
• /
• pp.59-66
• /
• 1997

Di(10-hemisuccinyloxy)decyl muconate(DDM) and di(6-hemisuccinyloxy)hexyl muconate(DHM) were synthesized, and showed a phase transition in an aqueous solution at 97 and $79^{\circ}C$, respectively. They did not form liposomes by themselves or even in the presence of cholesterol or dioleoylphosphatidylethanolamine(DOPE), but did form liposomes when they were mixed with phosphatidylcholine(PC). DHM molecules in liposome membranes were readily polymerized via 1,2-polymerization process on exposure to 254nm. Liposomes composed of DOPE/dioleoylphosphatidylcholine(DOPC)/DHM(3/3/1) were stable at neutral pH, but leaky at weakly acidic pH. The leakage of entrapped calcein from liposomes in phosphate-buffered saline (PBS, $37^{\circ}C$) of pH 4.8 and 5.8 was complete within 30 and 50 min, respectively. The release of toke entrapped calcein was increased with decreasing pH such that 50% and 100% of the calcein were released at pH near 5.5 and 5.0, respectively.

• Applied Chemistry for Engineering
• /
• v.4 no.2
• /
• pp.349-357
• /
• 1993

Polyarylate(PAR)-nylon 6 block copolymers of various block lengths were prepared by the anionic polymerization of ${\varepsilon}$-caprolactam using the polymeric activator from hydroxy-difuncrtional PAR and toluene diisocyanate. Phase separated morphology of PAR-nylon 6 block copolymer was suggerted from the thermal properties measured by differential scanning calorometry(d.s.c.). Partial miscbility between PAR block and nylon 6 block of the block copolymers was more evident at shorter length of constituent blocks. In binary blends of PAR-nylon 6 block copolymer with PAR or nylon 6 homopolymer, molecular-level mixing of homopolymers with corresponding blocks of block copolymer was supposed from the thermal properties measured by d.s.c..

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.08a
• /
• pp.281-281
• /
• 2010

Very low refractive index (<1.4) materials have been proved to be the key factor improving the performance of various optical components, such as reflectors, filters, photonic crystals, LEDs, and solar cell. Highly porous SiO2 are logically designed for ultralow refractive index materials because of the direct relation between porosity and index of refraction. Among them, ordered macroporous SiO2 is of potential material since their theoretically low refractive index ~1.10. However, in the conventional synthesis of ordered macroporous SiO2, the time required for the crystallization of organic nanoparticles, such as polystyrene (PS), from colloidal solution into well ordered template is typical long (several days for 1 cm substrate) due to the low interaction between particles and particle - substrate. In this study, polystyrene - polyacrylic acid (PS-AA) nanoparticles synthesized by miniemulsion polymerization method have hydrophilic polyacrylic acid tails on the surface of particles which increase the interaction between particle and with substrate giving rise to the formation of PS-AA film by simply spin - coating method. Less ordered with controlled thickness films of PS-AA on silicon wafer were successfully fabricated by changing the spinning speed or concentration of colloidal solution, as confirmed by FE-SEM. Based on these template films, a series of macroporous SiO2 films whose thicknesses varied from 300nm to ~1000nm were fabricated either by conventional sol - gel infiltration or gas phase deposition followed by thermal removal of organic template. Formations of SiO2 films consist of interconnected air balls with size ~100 nm were confirmed by FE-SEM and TEM. These highly porous SiO2 show very low refractive indices (<1.18) over a wide range of wavelength (from 200 to 1000nm) as shown by SE measurement. Refraction indices of SiO2 films at 633nm reported here are of ~1.10 which, to our best knowledge, are among the lowest values having been announced.

• Polymer(Korea)
• /
• v.27 no.6
• /
• pp.542-548
• /
• 2003

Nanoparticles with unsaturated poly(hydroxyalkanoate)s (UPHAs) biosynthesized with Pseudo-monas oleovorans were prepared by spontaneous emulsification solvent diffusion method. The influence of nanoparticle formation was investigated with various experimental parameters such as sonication conditions, sol-vent, surfactant and polymer contents, etc. The physical and chemical properties of UPHAS and its nanoparticles were characterized using $^1$H- and $\^$13/C-nuclear magnetic resonance spectroscopies, attenuated total reflection infrared spectroscopy, differential scanning calorimetry and gel permeation chromatography. The morphology of particles was observed using scanning electron microscope and the size and distribution of nanoparticles were measured with electrophoretic light scattering spectrophotometer. The mean diameter of particles decreased with increasing sonication amplitude and time. The addition of ethanol into UPHAS chloroform solution decreased the particle size presumably due to increased solvent diffusion into water phase. The particle size increased with increased the concentration of UPHAS solution. Under the 2-4％ poly(vinyl alcohol) (PVA) aqueous solution the minimum mean diameter of particles was shown. The higher degree of hydrolysis and degree of polymerization of PVA increased the mean diameter of particles.