• Polymer(Korea)
• /
• v.28 no.4
• /
• pp.314-320
• /
• 2004

Soluble aromatic polyimides bearing 4-(4-oxyalkyleneoxystyryl)- pyridines (ethylene and hexylene) as photoreactive side groups were synthesized and characterized. The photoreactive polymers were soluble in various polar organic solvents and their films were easily formed by solution casting. The photoreactivities of the polymers in the film state were approximately 64% at an exposure energy of 1.5 J/$\textrm{cm}^2$. Transmittances of the polymer films were about 85% after annealing at 20$0^{\circ}C$. Therefore, these polymers can be evaluated to be photoreactive polyimides with good transparency and solubility. The dichroic ratios of the polymers with ethylene and hexylene groups as the alkylene spacers were 0.023 and 0.026, respectively. The order parameters of 4'-pentyl-4-bipheny1carbonitrile as a liquid crystal (LC) in the film cells of the former and latter polymers were 0.50 and 0.52, respectively. These results indicate that the polymers show the effect of alkylene spacer on the photoalignments. The LC in the film cells of the polymers was perpendicularly oriented to the electric vector of the linear polarized UV light (LPUVL).

• Polymer(Korea)
• /
• v.35 no.4
• /
• pp.337-341
• /
• 2011

To expand the viewing angle of vertical alignment liquid crystal display (VA-LCD), a wide-band compensation film has been newly developed. VA-LCD needs a retardation film with improved oblique viewing property. The retardation film for VA-LCD has been fabricated by solvent casting and subsequent drawing triacetylcellulose (TAC) containing optical additives. Here, optical birefringence and wavelength dispersion of the retardation film strongly depend on the chemical structures of optical additives. Utilizing quantum mechanical computation, the polarizing anisotropy of retardation film was calculated with respect to additives. It is also realized that the wavelength dispersion of polarizing anisotropy depends on the type and location of substituent to the selected main isomer. When two propionates are substituted to the meta position of the selected main isomer, the wavelength dispersion of polarizing anisotropy shows the most gentle slop, which is well matched with the experimental results. The most gentle slop of wavelength dispersion means that the viewing angle characteristics of LCD are less influenced according to the wavelength of light source of LCD, and it's possible to make better image quality than the present level.

• Polymer(Korea)
• /
• v.35 no.4
• /
• pp.289-295
• /
• 2011

Biomaterials for retinal tissue engineering must demonstrate several critical features for potential utility, including mechanical integrity, biocompatibility, and slow biodegradation. Silk film biomaterials were designed and characterized to meet these functional requirements. We prepared natural/synthetic hybrid silk/PLGA films using 0, 10, 20, 40, and 80 wt% of silk by a solvent evaporation method. MIT assay was used to confirm the number of cells attached on film at 1, 2, and 3 days, respectively. The morphology of cellular adhesion on films was also confirmed by scanning electron microscope (SEM). RT-PCR was conducted to confrrm mRNA expression of retinal pigment epithelitun (RPE) using RPE65 as a RPEs marker and the expression of cytokeratin were determined by immunofluorescence staining. We confirmed that the silk/PLGA film of 20~40 wt% silk was superior for the adhesion and proliferation of RPEs.

• Polymer(Korea)
• /
• v.38 no.2
• /
• pp.164-170
• /
• 2014

This study was designed to find an appropriate biomaterial to proliferate Schwann cell (SC). Poly(lactic-co-glycolic acid) (PLGA) films mixed with demineralized bone particle (DBP), small intestine submucosa (SIS), and silk were fabricated by a solvent casting method. Analysis of MTT, SEM and RT-PCR were performed to confirm adhesion and proliferation of SC. Contact angle of films was assayed for hydrophilicity of films. We confirmed that PLGA/DBP 20% film showed higher hydrophilicity, promoted adhesion and proliferation of SC than other films. It was concluded that PLGA/DBP film can be applied for the scaffold biomaterials for the regeneration of central nerve system.

• Polymer(Korea)
• /
• v.33 no.2
• /
• pp.118-123
• /
• 2009

Keratin contains regulatory molecules that can enhance neuronal cell activity. We fabricated keratin/ PLGA films using 0, 10, 20, and 50 wt% of keratin using solvent casting method. We measured the contact angle of each film and cell proliferation was assayed by counting the cells attached on the film. Adhered cell morphology was confirmed by scanning electron microscope. RT-PCR was conducted to evaluate the gene expression of NF, NSE, and S-100, the Schwann cell markers. The keratin content of 20 and 50 wt% provided higher wettability than PLGA. The 20 wt% keratin was better in cell adhesion and proliferation of SCs than other keratin/PLGA films. The phenotypic stability of SC was maintained with the keratin content of 10 and 20 wt%.

• Polymer(Korea)
• /
• v.38 no.1
• /
• pp.54-61
• /
• 2014

Water-soluble sulfobetaine chitosan (SCs) was prepared for a blending film with Bombyx mori silk fibroin (SF) by reacting chitosan with 1,3-propanesultone. A series of SF/SCs blended films were successfully prepared by mixing aqueous solutions of B. mori SF and SCs. The SF/SCs blended films were examined through spectroscopic and thermal analysis to determine the morphological changes of SF in the SCs. The effects of the SF/SCs blend ratios on physical and mechanical properties were investigated to discover the feasibility of using these films as biomedical materials such as artificial skin and wound dressing. X-ray analysis showed good compatibility between the two biopolymers. The in vitro degradation behavior of the SF/SCs blended films was systematically investigated for up to 8 weeks in phosphate buffered saline solution at $37^{\circ}C$ and showed a mass loss of 46.4% after 8 weeks. All films showed no cytotoxicity by MC3T3-E1 assay. After 3 days of culture, the relative cell number on all the SF/SCs films was slightly lower than that of an optimized tissue culture plastic.

• Polymer(Korea)
• /
• v.32 no.2
• /
• pp.109-115
• /
• 2008

Because demineralized bone particle (DBP) contains various bioactive molecules such as cytokines, it is widely used biomaterials in the field of tissue engineering. In this study, we investigated the effect of 2-dimensional DBP/PLGA hybrid films on adhesion, proliferation and phenotype maintenance of intervertebral disc cells. PLGA films incorporated with different amount (0, 10, 20, 40 and 80 wt%) of DBP were prepared by the solvent evaporation method and characterized by scanning election microscopy (SEM). PLGA film has a flat and smooth surface. According to the increase of content of DBP, the surface of DBP/PLGA film exhibited few agglomerates and increased the roughness of the surface. Annulus fibrosus (AF) and nucleus pulposus (NP) cells were cultured on PLGA and DBP/PLGA film surface, and then examined the cell adhesion and proliferation by the cell count and SEM observation. The result of cell count and SEM observation revealed that 10 and 20% DBP in DBP/PLGA films were superior to adhesion and proliferation of both AF and NP cells. We confirmed that specific gene expression of disc cells on DBP/PLGA film based on the cell count result. Disc cells seeded on 20% DBP/PLGA film expressed the gene of type I and II collagen continuously. Therefore, pertinent content of biomaterials could provide more appropriate condition on adhesion and proliferation of cell. And this results may be used as a basic data for the intervertebral disc regeneration using tissue engineering.

• Polymer(Korea)
• /
• v.29 no.3
• /
• pp.237-241
• /
• 2005

Photocurable pentaerythritol modified hyperbranched acrylates were prepared from trimellitic anhydride, glycidyl methacrylate and pentaerythritol derivatives. Thermal stability obtained by using TGA showed that HBMA-1 was superior to the others. Hardness, abrasion resistance and tensile strength of HBMA-1 showed that Hey were also superior to the others. Value of yellow index of HBMA-1 showed the lowest.

• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.9
• /
• pp.78-85
• /
• 2008

Piezoelectric materials have been investigated as vibration energy converters to power wireless devices or MEMS devices due to the recent low power requirements of such devices and the advancement in miniaturization technology. Piezoelectric power generation can be an alternative to the traditional power source-battery because of the presence of facile vibration sources in our environment and the potential elimination of the maintenance required for large volume batteries. This paper represents the new power source which supplies energy device node. This system, called "energy harvesting system", with piezo materials scavenges extra energy such as vibration and acceleration from the environment. Then it converts the mechanical energy scavenged to electrical energy for powering device This paper explains the properties of piezo material through theoretical analysis and experiments The developed system provides a solution to overcome the critical problem of making up wireless device networks.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.33 no.10
• /
• pp.773-777
• /
• 2009

In this study, the strain sensing characteristics of single-wall carbon nanotubes(SWCNTs) networks were investigated to develop a film sensor for strain sensing. The SWCNTs film are formed on flexible substrates of poly(ethylene terephthalate) (PET) using spray process. In this manner we could control the transparency and obtain excellent uniformity of the networked SWCNT film. The carbon nanotube film is isotropic due to randomly oriented bundles of SWCNTs. Using experimental results it is shown that there is a nearly linear change in resistance across the film when it is subjected to tensile stress. The results presented in this study indicate the potential of such films for high sensitive transparent strain sensors on macro scale.