• Transactions on Electrical and Electronic Materials
• /
• v.3 no.1
• /
• pp.9-13
• /
• 2002

In this work, the surface of inorganic fillers were modified with some functional groups such as stearic acid, aliphatic long chain, vinylsilane and aminosilane to control the interaction between inorganic fillers and polymer matrix. Ethylene-vinyl acetate copolymers (EVA) with various amount of vinyl-acetate and copolyether-ester elastomer were used as polymer matrix. The addition of inorganic fillers increases flame retardancy, but results in steep drop of electrical and mechanical properties, which may be caused by the defects in the interface between organic/inorganic hybrid composites. The hybrid composites are found to show better mechanical properties and higher volume resistivities as inorganic fillers are well dispersed and have good adhesion with polymer matrix. Also, the most effective type of functional group coated on fillers depends on the chemical structure of polymer.

• Bulletin of the Korean Chemical Society
• /
• v.29 no.1
• /
• pp.135-138
• /
• 2008

Two bicarbazyl-containing fluorene copolymers, PFEBCz (95/5) and PFEBCz (75/25), were synthesized for white light electroluminescence from a single emitting polymer. All synthesized polymers were soluble in common organic solvents such as chloroform and toluene. The weight-average molecular weights (Mw) of the PFEBCz (95/5) and PFEBCz (75/25) copolymers were found to be 11,000 and 5,700 with polydispersity indices 1.4 and 1.8. The EL spectrum of the PFEBCz (75/25) device showed bright white-light emission with CIE coordinates of (0.32, 0.34) at 1000 cd/m2, which is very close to that for pure white (0.33, 0.33). This white emission may have been due to strong excimer formation between the bicarbazyl and fluorene polymer backbone. The device exhibited a maximum brightness of 3400 cd/m2 with a maximum efficiency of 0.2 cd/A.

• Polymer(Korea)
• /
• v.30 no.2
• /
• pp.97-107
• /
• 2006

In spite of excellent thermomechanical performance the majority of aromatic polyimides are so poor in processability due to their high backbone rigidity that their applications are greatly limited. The introduction of long side chains not only enhances their processiblity but also makes useful contribution to discovering new application fields. In this article, a variety of novel aromatic polyimides with flexible side chains were prepared either from new dimines or new dianhydrides to measure the influence of the side chains on structure and properties of the polymers and their new applications as liquid crystal alignment layers, photosensitive polymers, alternating multilayer nano-films and photoluminescent materials are discussed.

• Elastomers and Composites
• /
• v.55 no.4
• /
• pp.314-320
• /
• 2020

This study focused on experiments with polyethylene glycol (PEG) and glycidyl methacrylate (GMA), which are functional additives for water-expandable rubber. Polychloroprene rubber (CR)/superabsorbent polymer (SAP) composites were prepared and their cure behaviors, mechanical properties, water absorption rates, and surface morphology were measured based on the functional additives applied. When PEG and GMA were applied to the composites, the water absorption rate increased-including the initial rate-compared to that measured when functional additives were not used. The results also show that PEG has a hydrophilic functional group, which allows it to absorb more water, and GMA acts as a coupling agent between CR and SAP. However, with the introduction of functional additives, the cure rate slowed down and the mechanical properties also decreased.

• Proceedings of the Korean Fiber Society Conference
• /
• 2003.10a
• /
• pp.94-94
• /
• 2003

Cross-linked polystyrene (PS) particles with carboxyl and/or poly(ethylene glycol) units on surface were formed by an emulsifier-free emulsion polymerization using styrene, methacrylic acid (MA), and poly(ethylene glycol) dimethacrylate (PEG-diMMA) at pH 7, and followed by freeze-drying to give the corresponding powders. Monodisperse polymer particles could be obtained at a concentration of PEG-diMMA 1 mol% relative to styrene. Zeta potential of polymer surface was measured to be 91 mV at a polymer of PEG-diMMA 1 mol% and was dropped as the content of MA increased.

• ETRI Journal
• /
• v.26 no.4
• /
• pp.285-291
• /
• 2004

We prepared a novel multi-functional dual-layer polymer electrolyte by impregnating the interconnected pores with an ethylene carbonate (EC)/dimethyl carbonate (DMC)/lithium hexafluorophosphate $(LiPF_6)$ solution. The first layer, based on a microporous polyethylene, is incompatible with a liquid electrolyte, and the second layer, based on poly (vinylidenefluoride-co-hexafluoropropylene), is submicroporous and compatible with an electrolyte solution. The maximum ionic conductivity is $7{\times}10^{-3}S/cm$ at ambient temperature. A unit cell using the optimum polymer electrolyte showed a reversible capacity of 198 mAh/g at the 500th cycle, which was about 87% of the initial value.

• Macromolecular Research
• /
• v.16 no.7
• /
• pp.631-636
• /
• 2008

The intrinsic viscosities were determined for poly(DL-lactic acid) (PDLLA) solutions in 1,2-dialkyl phthalate at temperatures ranging from 30 to $60^{\circ}C$. A series of dialkyl phthalate, in which the alkyl group was changed from methyl to propyl, was used as the solvent to control the solvent quality systematically. The intrinsic viscosity of the PDLLA solution was higher in the better quality solvent, with a higher molecular weight of PDLLA, and at lower temperatures. The unperturbed dimensions of the PDLLA molecule and polymer-solvent interaction parameter of PDLLA in dialkyl phthalate were deduced using extrapolation methods based on the temperature-dependent intrinsic viscosities. Slight shrinkage in the unperturbed chain dimension was observed, which resulted from a change in polymer conformation with temperature. It was also observed that the polymer-solvent interaction became more favorable with the dialkyl phthalate containing a shorter alkyl chain.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.522-522
• /
• 2013

Plasma can be used to various applications such as sterilization, inactivation/removal of microorganisms, wound healing, tooth bleaching, cancer treatment, surface modification and plasma polymerization. In this research, we studied the effect of plasma irradiation on the structural, optical, and biological properties of the polymer films. Several polymers were synthesized and then deposited on the glass substrates. The polymer films were treated by oxygen and nitrogen plasmas. Plasma-treated films were investigated by contact angle, infrared absorption spectroscopy, cathodoluminescence spectroscopy, and scanning electron microscopy. Functional materials were prepared on plasma-treated surface, and their performances were investigated using various techniques. Next, we discuss relationship between the performance of functional materials and the structural properties of plasma-treated polymer films.

• Fibers and Polymers
• /
• v.1 no.2
• /
• pp.83-91
• /
• 2000

Thermotropic liquid crystalline polymer made up of poly(p-hydroxybenzoate) (PHB)-poly(ethylene terephthalate)(PET) 8/2 copolyester, poly(ethylene 2,6-naphthalate) (PEN) and PET were mechanically blended to pursue the liquid crystalline phase of ternary blends. Complex viscosities of blends decreased with increasing temperature and PHB content. DSC thermal analysis indicated that glass transition temperature (Tg) and melting temperature (Tm) of blends increased with increasing PHB content. Both tensile strength and initial modulus increased with raising PHB content and take-up speed of monofilaments. In the WAXS diagram, only PEN crystal reflection at 2Θ=$15.5^{\circ}C$ appeared but PET crystal reflection was not shown in all compositions. The degree of transesterification and randomness of blends increased with blending time but sequential length of both PEN and PET segment decreased.

• Polymer Science and Technology
• /
• v.8 no.6
• /
• pp.707-714
• /
• 1997