• ETRI Journal
• /
• v.27 no.2
• /
• pp.181-187
• /
• 2005

Alkoxy-substituted poly(spirobifluorene)s and their copolymers with a triphenylamine derivative have been synthesized by Ni(0)-mediated polymerization. The polymers were well soluble in common organic solvents. Pure blue-light emissions without the long wavelength emission of poly(fluorene)s have been observed in the fluorescence spectra of polymer thin films. The light emitting diodes with a device configuration of ITO/PEDT:PSS(30 nm)/polymer(60 nm)/LiF(1 nm)/Al(100 nm) have been fabricated. The electroluminescence spectra showed the blue emissions without the long wavelength emission as observed in the fluorescence spectra. The relatively poor electroluminescence quantum yield of the homopolymer (0.017% @ 20 $mA/cm^{2}$) with color coordinates of (0.16, 0.07) has been improved by the introduction of triphenylamine moiety, and the copolymer with derivative exhibited an electroluminescence quantum yield of 0.15 % at 20 $mA/cm^{2}$ with color coordinates of (0.16, 0.08). Moreover, the introduction of polar side chains to the spirobifluorene moiety enhanced the device performance and led to the quantum yields of 0.6 to 0.7 % at 20 $mA/cm^{2}$, although there was some expense of color purities.

• 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.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2003.10a
• /
• pp.1-2
• /
• 2003

While aromatic polyimides and polyamides have found widespread use as high performance polymers, the present work addressed the need for organosoluble materials through the use of a hyperbranching scheme. The $AB_2$ monomers were prepared. The $AB_2$ monomers were then polymerized via aromatic fluoride-displacement and Yamazaki reactions to afford the corresponding hydroxyl-terminated hyperbranched polyimides (HT-PAEKI) and amine-terminated hyperbranched polyamides, respectively. HT-FAEKI was then functionalized with allyl and propargyl bromides as well as epichlorohydrin to afford allyl-terminated AT-PAEKI, propargyl-terminated PT-PAEKI, and epoxy (glycidyl)-terminated ET-PAEKI, in that order. All hyperbranched poly(ether-ketone-imide)s were soluble in common organic solvents. AT-PAEKI was blended with a bisphenol-A-based bismaleimide (BFA-BMI) in various weight ratios. Thermal, rheological, and mechanical properties of these blend systems were evaluated. Two characteristic hyperbranched polyamides, which the one has para-electron donating groups to the surface amine groups and the other has para-electron withdrawing groups to the surface amine groups, were selected to compare BMI curing behaviors. The electron rich polymer displayed ordinary Michael addition type exothermic reaction, while electron deficient polymer did display unusual curing behaviors. Based on analytical data, the later system provided the strong evidences to support room temperature curing of BMI by reactive intermediates instead of reactive primary amine groups on the macromolecule surface.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2003.10a
• /
• pp.25-28
• /
• 2003

Carbon nanotubes(CNTs), since their first discovery, have been considered as new promising materials in various fields of applications including field emission displays, memory devices, electrodes, NEMS constituents, hydrogen storages and reinforcements in composites due to their extra-ordinary properties. The carbon nanotube reinforced nanocomposites have attracted attention owing to their outstanding mechanical and electrical properties and are expected to overcome the limit of conventional materials. Various application areas are possible for carbon nanotube reinforced nanocomposites through the functionalization of carbon nanotubes. Carbon nanotube reinforced polymer matrix nanocomposites have been fabricated by liquid phase process including surface functionalization and dispersion of CNTs within organic solvent. In case of carbon nanotube reinforced polymer matrix nanocomposites, the mechanical strength and electrical conducting can be improved by more than an order of magnitude. The carbon nanotube reinforced polymer matrix nanocomposites can be applied to high strength polymers, conductive polymers, optical limiters and EMI materials. In spite of successful development of carbon nanotube reinforced polymer matrix nanocomposites, the researches on carbon nanotube reinforced inorganic matrix nanocomposites show limitations due to a difficulty in homogeneous distribution of carbon nanotubes within inorganic matrix. Therefore, the enhancement of carbon nanotube reinforced inorganic nanocomposites is under investigation to maximize the excellent properties of carbon nanotubes. To overcome the current limitations, novel processes, including intensive milling process, sol-gel process, in-situ process and spark plasma sintering of nanocomposite powders are being investigated. In this presentation, current research status on carbon nanotube reinforced nanocomposites with various matrices are reviewed.

• Journal of Information Display
• /
• v.5 no.4
• /
• pp.12-17
• /
• 2004

A series of statistical random copolymers of dioctylfluorene (DOF) and 3,4-ethylenedioxythiophene (EDOT) were synthesized by Ni (0) mediated polymerization and their light-emitting properties were compared with poly (9,9-di-n-octylfluorene) (PDOF). The synthesized polymers were characterized using UV-vis spectroscopy, TGA, photoluminescence (PL) & electroluminescence (EL) spectroscopy and by conducting molecular weight studies. The resulting polymers were found to be thermally stable and readily soluble in organic solvents. The UV-visible absorption and PL emission spectra of the copolymers were gradually red-shifted as the fraction of EDOT in copolymers increased. Light-emitting devices were fabricated in an ITO (indium-tin oxide)/PEDOT/polymer/Ca/Al configuration. Interestingly, the EL spectra of these devices were similar to the PL spectra of the corresponding polymer film. However, the EL devices constructed from the copolymer showed more than 10 times higher efficiency level than the devices constructed from the PDOF homopolymer. This higher efficiency is possibly the result of better charge carrier balance in the copolymer systems due to the lower HOMO levels of the copolymers in comparison to that of PDOF homopolymer.

• Macromolecular Research
• /
• v.12 no.4
• /
• pp.407-412
• /
• 2004

A new hydroxyl group-containing conjugated ionic polymer, poly[2-ethynyl-N-(p-hydroxyphenylethyl)pyridinium bromide], was synthesized by the activated polymerization of 2-ethynylpyridine with p-(2-bromoethyl) phenol without any additional initiator or catalyst. The polymerization proceeded well to give a moderate yield (65%) of polymer at a reaction temparature of 90$^{\circ}C$. Another polymer, poly[2-ethynyl-N-(p-hydroxyphenylethyl)pyridinium tetraphenylborate], was readily prepared by the ion-exchange reaction of poly[2-ethynyl-N-(p-hydroxyphenylethyl)pyridinium bromide] with sodium tetraphenylborate. These polymers were completely soluble in organic solvents such as DMF, DMSO, and acetone, but insoluble in water and ether. Instrumental analyses, such as NMR, IR, and UV-Vis spectroscopies, indicated that the new materials have conjugated polymer backbone systems with the designed substituents and counter anions. X-Ray diffraction analyses of the polymers indicated that they were mostly amorphous.

• Macromolecular Research
• /
• v.14 no.5
• /
• pp.524-529
• /
• 2006

New, thermally robust, arylenevinylene conjugated polymers, including poly(9,9-dioctylfluorenyl-2,7-vinylene) [poly(FV)] and poly[2-(3'-dimethyldodecylsilylphenyl)-1,4-phenylenevinylene] [poly(m-SiPhPV)], were synthesized and used for the fabrication of efficient photovoltaic cells. Bulk heterojunction photovoltaic cells fabricated by blending one of the polymers, [poly(FV)], [poly(m-SiPhPV)], and poly(FV-co-m-SiPhPV), with the fullerene derivative [6,6]-phenyl-$C_{61}$-butyric acid methyl ester (PCBM) were found to have a power conversion efficiency of up to 0.038%..

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2012.05a
• /
• pp.51-51
• /
• 2012

There is a growing interest in innovative chemical synthesis in microreactors owing to high efficiency, selectivity, and yield. In microfluidic systems, the low-volume spatial and temporal control of reactants and products offers a novel method for chemical manipulation and product generation. Glass, silicon, poly(dimethylsiloxane) (PDMS), and plastics have been used for the fabrication of miniaturized devices. However, these materials are not the best due to either of low chemical durability or expensive fabrication costs. In our group, we have recently addressed the demand for economical resistant materials that can be used for easy fabrication of microfluidic systems with reliable durability. We have suggested the use of various specialty polymers such as silicon-based inorganic polymers and fluoropolymer, flexible polyimide (PI) films that have not been used for microfluidic devices, although they have been used for other areas. And inexpensive lithography techniques were used to fabricate Lab-on-a-Chip type of microreactors with differently devised microchannel design. These microreactors were demonstrated for various synthetic reactions: liquid, liquid-gas organic chemical reactions in heterogeneous catalytic processes, syntheses of polymer and non-trivial inorganic materials. The microreactors were inert, and withstand even harsh conditions, including hydrothermal reaction. In addition, various built-in microstructures inside the microchannels, for example Pd decorated peptide nanowires, definitely enhance the uniqueness and performance of microreactors. These user-friendly Lab-on-a-Chip devices are useful alternatives for chemist and chemical engineer to conventional chemical tools such as glass.

• Bulletin of the Korean Chemical Society
• /
• v.29 no.5
• /
• pp.933-938
• /
• 2008

2,4-Di-(2'-hydroxyethoxy)benzylidenemalononitrile (3) was prepared and polymerized with terephthaloyl chloride and adipoyl chloride to yield novel Y-type polyesters 4 and 5 containing dioxybenzylidenemalononitrile groups as NLO-chromophores, which constituted parts of the polymer backbone. The resulting polymers 4 and 5 are soluble in common organic solvents such as acetone and N,N-dimethylformamide. Polymers 4 and 5 showed thermal stability up to 300 ${^{\circ}C}$ in thermogravimetric analysis with glass-transition temperatures obtained from differential scanning calorimetry in the range 83-94 ${^{\circ}C}$. The second harmonic generation (SHG) coefficients ($d_{33}$) of poled polymer films at the 1064 nm fundamental wavelength were around $6.48\;{\times}\;10^{-9}$ esu. The dipole alignment exhibited high thermal stability even at 10 ${^{\circ}C}$ higher than $T_g$ and no significant SHG decay was observed below 105 ${^{\circ}C}$ partially due to the main-chain character of polymer structure, which is acceptable for NLO device applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.07a
• /
• pp.779-782
• /
• 2000

Silicone rubbers are first silicone polymers and has named silicone from existence of Si-O bond similar to Keton. Silicon in organic compound has been called silicone, and linear or network polymers. Silicone rubbers have been used as an power insulator because they are well weather proof, ozone proof and have excellent electric characteristics, thermal stability, cold resistance and low surface energy. Especially, it is known that they have very excellent characteristics at 200[$^{\circ}C$]. For this study, we made silicone rubbers as specimens and we measured dielectric loss tangent due to applied voltage at temperature range 25[$^{\circ}C$] to 180[$^{\circ}C$] and frequency range 20[Hz] to 1${\times}$10$\^$6/[Hz] to examine dielectric properties. We measured dielectric loss tangent to study the insulation performance of silicone rubbers.