• Polymer(Korea)
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• v.25 no.4
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• pp.545-557
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• 2001

The crosslinked films retaining cholesteric liquid-crystalline order were prepared by casting the liquid crystalline solutions of hydroxypropyl cellulose (HPC) in methanol with the two kinds of aliphatic dicarboxylic acid chlorides (succinyl chloride and suberoyl chloride). The temperature dependence on the cholesteric pitch of the crosslinked films and the swelling behavior of the films in both water and methanol were investigated. The films displayed fingerprint patterns charateristic of cholesteric liquid-crystalline phase, and their pitches, as well as HPC itself, increased with temperature. However, the pitch of all crosslinked samples was much greater than that of HPC at the same temperature and increased with increasing concentration and chain length of the crosslinker. The crosslinked samples exhibited an anisotropic swelling in both solvents. The degree of anisotropy slightly depended on the solvent and crosslinker species, but hardly on the crosslinker concentration investigated.

• Macromolecular Research
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• v.12 no.4
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• pp.422-426
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• 2004

Solid polymer electrolytes based on poly(ethylene glycol)-polyurethane (PEG-PU) complexed with LiClO$_4$ salt have been prepared by the solvent casting method. A PEG-PU material (PEG:4,4'-diphenylmethane diisocyanate: l,4-butanediol = 1:2:1) was synthesized through a typical two-step condensation reaction. We investigated the effects of the salt concentration on the ionic conductivity ($\sigma$) and the glass transition temperature (T$_{g}$ ) of the complex electrolytes by using alternating current impedance spectroscopy, differential scanning calorimetry, and dynamic mechanical thermal analysis. The measured values of both $\sigma$ and T$_{g}$ exhibited similar tendencies in that they had maxima within the range studied, probably because of two opposite effects, i.e., the increased number of carrier ions and the decreased chain mobility (or increased T$_{g}$ ) caused by the increase in the salt concentration. The highest conductivity, on the order of 2.43 ${\times}$ 10$^{6}$ S$cm^{-1}$ /, was obtained at an [O]/[Li$^{+}$] ratio of ca. 16 (0.92 ㏖ salt per kg of matrix polymer).

• Macromolecular Research
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• v.13 no.5
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• pp.446-452
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• 2005

The interactions between the surface of scaffolds and specific cells play an important role in tissue engineering applications. Some cell adhesive ligand peptides including Arg-Gly-Asp (RGD) have been grafted into polymeric scaffolds to improve specific cell attachment. In order to make cell adhesive scaffolds for tissue regeneration, biodegradable nonporous poly(L-lactic acid) (PLLA) films were prepared by using a solvent casting technique with chloroform. The hydrophobic PLLA films were surface-modified by Argon plasma treatment and in situ direct acrylic acid (AA) grafting to get hydrophilic PLLA-g-PAA. The obtained carboxylic groups of PLLA-g-PAA were coupled with the amine groups of Gly-Arg-Asp-Gly (GRDG, control) and GRGD as a ligand peptide to get PLLA-g-GRDG and PLLA-g-GRGD, respectively. The surface properties of the modified PLLA films were examined by various surface analyses. The surface structures of the PLLA films were confirmed by ATR-FTIR and ESCA, whereas the immobilized amounts of the ligand peptides were 138-145 pmol/$cm^2$. The PLLA surfaces were more hydrophilic after AA and/or RGD grafting but their surface morphologies showed still relatively smoothness. Fibroblast adhesion to the PLLA surfaces was improved in the order of PLLA control

• Polymer(Korea)
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• v.33 no.3
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• pp.203-206
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• 2009

Polyaniline Emeraldine salt (PANI-salt) prepared by the common chemical oxidative polymerization caused the corrosion of the metallic injection mold by protonic acid such as HCl which used as a dopant. PANI-salt, polyaniline doped with dodecylbenzenesulfonic acid (DBSA), was obtained by the emulsion polymerization in nonpolar organic solvent, toluene. In this study DBSA was used as a dopant along with a surfactant. PANI-salt and high impact polystyrene (HIPS) have a good solubility in toluene. Blends with different ratio of PANI and HIPS were prepared through a solution-cast blending. The structure of PANI-salt was characterized by FT-IR and UV-Vis. The morphology, thermal, and electrical properties for PANI-HIPS blends were investigated. Injection molded under $103^{\circ}C$, 120 psi, PANI-HIPS showed the highest electrical conductivity ($6.02{\times}10^{-5}\;S/cm$) after blending PANI (50 mL) and HIPS (1 g).

• Elastomers and Composites
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• v.44 no.2
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• pp.106-111
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• 2009

Tissue engineering is a research field for artificial substitutes to improve or replace biological functions. Scaffolds play a important role in tissue engineering. Scaffold porosity and pore size provide adequate space, nutrient transportation and cell penetration throughout the scaffold structure. Scaffold structure is directly related to fabrication methods. This review will introduce the current technique of 3D scaffold fabrication for tissue engineering. The conventional technique for scaffold fabrication includes salt leaching, gas foaming, fiber bonding, phase seperation, melt moulding, and freeze drying. These conventional scaffold fabrication has the limitations of cell penetration and interconnectivity. In this paper, we will present the solid freeform fabrication (SFF) such as stereolithography (SLA), selective laser sintering (SLS), and fused deposition modeling (FDM), and 3D printing (3DP).

• Membrane Journal
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• v.17 no.4
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• pp.277-286
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• 2007

The technology of seawater desalination has been received much attentions to solve the problem of water shortage through all over the world. In this study, it attempts to confirm the use-possibility of cellulose triacetate (CTA) for preparation of reverse osmosis membranes which have been highlighted as high efficiency and low energy consumption process for seawater desalination. The effects of casting dope parameters like an acetyl content, solvent, additives on the membrane performance were investigated. It was possible to produce the membranes which have high water flow rate and salt rejection with the increase of acetyl content and dioxane content among various dioxane/acetone ratios. Acetic acid and maleic acid were preferred for additives to produce high performance membranes. It was verified that $HOLLOSEP^{(R)}$ module which is commercialized CTA membrane by TOYOBO Co. can produce stable water production and high-quality water for long-term operation in the practice plants without any chemical treatments.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1229-1232
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• 1994

The purpose of this study is to research and develop solid polymer electrolyte(SPE) for Li secondary battery. This paper describes the effects of lithium salts, plasticizer addition and temperature dependence of conductivity of PEO electrolytes. Polyethylene oxide(PEO) based polymer electrolyte films were prepared by solution casting an acetonitrile solution of preweighed PEO and Li salt. After solvent evaporation, the electrolyte films were vacuum-dried at $60^{\circ}C$ for 48h, the thickness of the films were $90{\sim}110{\mu}m$. The conductivity properties of prepared PEO electrolytes are summarized as follows. PEO electrolyte complexed with $LiClO_4$ shows the better conductivity of the others. $PEO-LiClO_4$ electrolyte when $EO/Li^+$ ratio is 8, showed the best conductivity. Optimum operating temperature of PEO electrolyte is $60^{\circ}C$. By adding propylene carbonate and ethylene carbonate to $PEO-LiClO_4$ electrolyte, its conductivity was higher than $PEO-LiClO_4$ without those. Also $PEO_8LiClO_4$ electrolyte remains static up to 4.5V vs. $Li/Li^+$.

• Resources Recycling
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• v.7 no.4
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• pp.35-42
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• 1998

Surface mount technology is the biggest theme in the area of deιIronic component. To miniatunze an electronic component, s such as ferrite chip inductor, the cer뼈lic wet process for green-sheet lamination and/or screen printing method through a s solvent medium system is widely used. The preparation and characterization of NiCuZn Ferrite (NCZF) shurry and the green s sheet using the water mixed binder system has been studied. The 21 vol% of NCZF slurry was prepared by a ball milling. The p polyacrylic vinyl copolymer (Mw; 60,000) was used as a binder. Th$\xi$ mixture of distilled water, isopropyl alcohol (IPA) and 2l butoxy ethanol was used as a dispersion medium. The water content of medium varied from about 40% to 80%. As the results. Thc disp$\xi$rston stability of the NCZF slurry was attributed to the free polymer rather than the electrostatic force of the particle. T The viscosity of the NCZF slurry was greatly depended on the ratio of water content in the medium.

• Journal of Biomedical Engineering Research
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• v.27 no.5
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• pp.218-223
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• 2006

We examined the effects of ${\beta}$-glucan-reinforced PLGA film and scaffold on HDFs (human dermal fibroblast) attachment and proliferation. The PLGA films were prepared by simple solvent-casting method. The prepared films were grafted with $(1{\to}3)(1{\to}6)-{\beta}-glucan$ in various ratios after plasma treatment on surface. The surface of the film was characterized by contact angle measurement, scanning electron microscope (SEM), and Fourier-transform infrared spectrophotometer (FT-IR). The amount of $(1{\to}3)(1{\to}6)-{\beta}-glucan$ in the prepared film was indirectly determined by phenol-sulfuric acid method. The HDFs (Human dermal fibroblasts) were used to evaluate the cell attachment and proliferation on PLGA specimens before and after plasma/${\beta}-glucan$ treatment. The result showed that the plasma treated groups exhibited more mont of ${\beta}-glucan$ might be grafted than the non plasma treated groups. Cell attachment was significantly enhanced in the plasma/${\beta}-glucan$ grafted group after 4 hours incubation (p<0.05) due to the improved hydrophilicity and cytoactivity effect of the ${\beta}-glucan$. The cell proliferation of plasma/${\beta}-glucan$ (2mg/ml) grafted group was the highest rate among the groups (p<0.05).

• Membrane and Water Treatment
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• v.12 no.1
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• pp.43-49
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• 2021

The Commercial polymeric membranes like Polysulfone (PSF), Polyvinylidene difluoride (PVDF) and Polyacrylonitrile (PAN) which are an integral part of water purification investigation were chosen for the shockwave (SW) exposure experiment. These membranes were prepared by blending polymer (wt. %) / DMF (solvent) followed by phase-inversion casting technique. Shockwaves are generated by using Reddy Tube lab module (Table-top Shocktube) with range of pressure (1.5, 2.5 and 5 bar). Understanding the changes in membrane before and after shock wave treatment by parameters, i.e., pure water flux (PWF), rejection (%), porosity, surface roughness (AFM), morphology (SEM) and contact angle which can significantly affect the membrane's performance. Flux values PSf membranes shows increase, 465 (pristine) to 524 (1.5wt%) LMH at 50 Psi pressure and similar enhancement was observed at 100Psi (625 to 696 LMH). Porosity also shows improvement from 73.6% to 76.84% for 15wt% PSf membranes. It was observed that membranes made of polymers such as PAN and PSF (of high w/w %) exhibits some resistance against shockwaves impact and are stable compared to other membranes. Shockwave pressure of up to 1.5 bar was sufficient enough to change properties which are crucial for performance. Membranes exposed to a maximum pressure of 5 bar completely scratched the surface and with minimum pressure of 1.5bar is optimum enough to improve the water flux and other parameters. Initial results proved that SW may be suitable alternative route to minimize/control membrane fouling and improve efficiency.