• Title, Summary, Keyword: Polymer precursor

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Stabilization, Carbonization, and Characterization of PAN Precursor Webs Processed by Electrospinning Technique

  • Cho, Chae-Wook;Cho, Dong-Hwan;Ko, Young-Gwang;Kwon, Oh-Hyeong;Kang, Inn-Kyu
    • Carbon letters
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    • v.8 no.4
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    • pp.313-320
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    • 2007
  • In the present study, electrospun PAN precursor webs and the stabilized and carbonized nanofiber webs processed under different heat-treatment conditions were characterized by means of weight loss measurement, elemental analysis, scanning electron microscopy (SEM), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC), thermogravimentric analysis (TGA), and X-ray diffraction (XRD) analysis. The result indicated that stabilization and carbonization processes with different temperatures and heating rates significantly influenced the chemical and morphological characteristics as well as the thermal properties of the stabilized and then subsequently carbonized nanofiber webs from PAN precursor webs. It was noted that the filament diameter and the carbon content of a carbonized nanofiber web as well as its weight change may be effectively monitored by controlling both stabilization and carbonization processes.

A Water-Soluble Polyimide Precursor: Synthesis and Characterization of Poly(amic acid) Salt

  • Lee, Myong-Hoon;Jun Yang
    • Macromolecular research
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    • v.12 no.3
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    • pp.263-268
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    • 2004
  • We have synthesized a water-soluble polyimide precursor, poly(amic acid) amine salt (PAD), from pyromellitic dianhydride (PMDA), 4,4'-oxydianiline, and N,N -dimethylethanolamine (DMEA) and have investigated in detail its properties with respect to the degree of salt formation (D$\_$sf/). The maximum value of D$\_$sf/ we obtained upon precipitation of the precursor solution into acetone was 79%. We synthesized a PAD having a D$\_$sf/ of 100% (PAD100) by the solid state drying of an organic solution. The precursors showed different solubility depending on the D$\_$sf/ to make up to 4 wt% solutions in water containing a small amount of DMEA. PAD100 is completely soluble in pure water. We investigated the imidization behavior of PAD in aqueous solution using various spectroscopic methods, which revealed that PAD 100 has faster imidization kinetics relative to that of the poly(amic acid)-type precursors. The resulting polyimide films prepared from an aqueous precursor solution possess almost similar physical and thermal properties as those prepared from N-methyl-2-pyrrolidone(NMP) solution. Therefore, we have demonstrated that PAD can be used as a water-based precursor of polyimide; this procedure avoids the use of toxic organic solvents, such as NMP.

Fabrication of Carbon Microcapsules Containing Silicon Nanoparticles-Carbon Nanotubes Nanocomposite for Anode in Lithium Ion Battery

  • Bae, Joon-Won;Park, Jong-Nam
    • Bulletin of the Korean Chemical Society
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    • v.33 no.9
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    • pp.3025-3032
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    • 2012
  • Carbon microcapsules containing silicon nanoparticles (Si NPs)-carbon nanotubes (CNTs) nanocomposite (Si-CNT@C) have been fabricated by a two step polymerization method. Silicon nanoparticles-carbon nanotubes (Si-CNT) nanohybrids were prepared with a wet-type beadsmill method. A polymer, which is easily removable by a thermal treatment (intermediate polymer) was polymerized on the outer surfaces of Si-CNT nanocomposites. Subsequently, another polymer, which can be carbonized by thermal heating (carbon precursor polymer) was incorporated onto the surfaces of pre-existing polymer layer. In this way, polymer precursor spheres containing Si-CNT nanohybrids were produced using a two step polymerization. The intermediate polymer must disappear during carbonization resulting in the formation of an internal free space. The carbon precursor polymer should transform to carbon shell to encapsulate remaining Si-CNT nanocomposites. Therefore, hollow carbon microcapsules containing Si-CNT nanocomposites could be obtained (Si-CNT@C). The successful fabrication was confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). These final materials were employed for anode performance improvement in lithium ion battery. The cyclic performances of these Si-CNT@C microcapsules were measured with a lithium battery half cell tests.

Renal Precursor Cell Transplantation Using Biodegradable Polymer Scaffolds

  • KIM , SANG-SOO;PARK, HEUNG-JAE;HAN, JOUNG-HO;PARK, MIN-SUN;PARK, MOON-HYANG;SONG, KANG-WON;JOO, KWAN-JOONG;CHOI, CHA-YONG;KIM, BYUNG-SOO
    • Journal of Microbiology and Biotechnology
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    • v.15 no.1
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    • pp.105-111
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    • 2005
  • End-stage renal disease is a fatal and devastating disease that is caused by progressive and irreversible loss of functioning nephrons in the kidney. Dialysis and renal transplantation are the common treatments at present, but these treatments have severe limitations. The present study investigated the possibility of reconstructing renal tissues by transplantation of renal precursor cells to replace the current treatments for end-stage renal disease. Embryonic renal precursor cells, freshly isolated from metanephroi of rat fetus at day 15 post-gestation, were seeded on biodegradable polymer scaffolds and transplanted into peritoneal cavities of athymic mice for three weeks. Histologic sections stained with hematoxylin & eosin and periodic acid-Schiff revealed the formation of primitive glomeruli, tubules, and blood vessels, suggesting the potential of embryonic renal precursor cells to reconstitute renal tissues. Immunohistochemical staining for proliferating cell nuclear antigen, a marker of proliferating cells, showed intensive nuclear expression in the regenerated renal structures, suggesting renal tissue reconstitution by transplanted embryonic renal precursor cells. This study demonstrates the reconstitution of renal tissue in vivo by transplanting renal precursor cells with biodegradable polymer scaffolds, which could be utilized as a new method for partial or full restoration of renal structure and function in the treatment of end-stage renal disease.

Novel Preparation of Epoxy/Silica Nanocomposite Using Si-N Precursor (Si-N 전구체를 이용한 에폭시/실리카 나노복합재료의 제조)

  • Kim Lee Ju;Yoon Ho Gyu;Lee Sang-Soo;Kim Junkyung
    • Polymer Korea
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    • v.28 no.5
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    • pp.391-396
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    • 2004
  • In order to overcome drawbacks in the conventional preparation of epoxy/silica nanocomposites, such as formation of micro voids and dimensional instability caused by evolution of volatile by-products during curing reaction, a novel preparation method using Si-N precursor has been proposed. When prepared through in-situ reaction of epoxy curing reaction with sol-gel reaction of Si-N precursor, methyltripiperidinylsilane (MTPS) which does not produce by-products during reaction, epoxy/silica nanocomposites of extremely even dispersion of inorganic phase could be successfully prepared, resulting in high enhancement of mechanical and thermal properties as well as outstanding transparency.

Facile Approach to Magnetic Carbon Nanoparticles using an Iron-Doped Polymer Precursor

  • Yoon, Hyeon-Seok;Jang, Jyong-Sik
    • Proceedings of the Polymer Society of Korea Conference
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    • pp.283-283
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    • 2006
  • Multigram-scale product exclusively containing magnetic carbon nanoparticles (MNCPs) with uniform size was successfully fabricated without a specific separation process. The iron-doped PPy nanoparticles were synthesized by micelle templating and used as the carbon precursor in order to generate MCNPs. The magnetic carbon nanoparticles possessed a microporous structure and exhibited ferromagnetic properties at room temperature. This approach may be an effective alternative to generate magnetic carbon nanoparticles against the conventional arc-discharge technique.

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Nanostructured Bulk Ceramics (Part IV. Polymer Precursor Derived Nanoceramics)

  • Han, Young-Hwan;Mukherjee, Amiya K.
    • Journal of the Korean Ceramic Society
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    • v.47 no.3
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    • pp.205-209
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    • 2010
  • In the last (fourth) section, the discussion will entail a silicon-nitride/silicon-carbide nanocomposite, produced by pyrolysis of liquid polymer precursors, demonstrating one of the lowest creep rates reported so far in ceramics at the comparable temperature of $1400^{\circ}C$. This was first achieved by avoiding the oxynitride glass phase at the intergrain boundaries. One important factor in the processing of these nanocomposites was the use of the electrical field assisted sintering method.

Patterned Fluorescence Images with a t-Boc-Protected Coumarin Derivative

  • Min Sung-Jun;Park Bum Jun;Kim Jong-Man
    • Macromolecular research
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    • v.12 no.6
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    • pp.615-617
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    • 2004
  • We have developed an efficient method for the generation of patterned fluorescence images using a protected precursor molecule. The t-Boc-protecting group of a coumarin derivative was readily removed from a polymer film upon irradiation with UV light in the presence of a photoacid generator to provide the original properties of the coumarin. Fine fluorescence patterns were obtained when using this photolithographic method.

The Study on Characteristics of N-Doped Ethylcyclohexane Plasma-Polymer Thin Films

  • Seo, Hyeon-Jin;Jo, Sang-Jin;Lee, Jin-U;Jeon, So-Hyeon;Bu, Jin-Hyo
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.540-540
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    • 2013
  • In this studying, we investigated the basic properties of N-doped plasma polymer. The N-doped ethylcyclohexane plasma polymer thin films were deposited by radio frequency (13.56 MHz) plasma-enhanced chemical vapor deposition method. Ethylcyclohexenewas used as organic precursor (carbon source) with hydrogen gas as the precursor bubbler gas. Additionally, ammonia gas [NH3] was used as nitrogen dopant. The as-grown polymerized thin films were analyzed using ellipsometry, Fourier-transform infrared [FT-IR] spectroscopy, Raman spectroscopy, FE-SEM, and water contact angle measurement. The ellipsometry results showed the refractive index change of the N-doped ethylcyclohexene plasma polymer film. The FT-IR spectrashowed that the N-doped ethylcyclohexene plasma polymer films were completely fragmented and polymerized from ethylcyclohexane.

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High Performance Polyimides for Applications in Microelectronics and Flat Panel Displays

  • Ree Moonhor
    • Macromolecular research
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    • v.14 no.1
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    • pp.1-33
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    • 2006
  • Polyimides (PIs) exhibit excellent thermal stability, mechanical, dielectric, and chemical resistance properties due to their heterocyclic imide rings and aromatic rings on the backbone. Due to these advantageous properties, PIs have found diverse applications in industry. Most PIs are insoluble because of the nature of the high chemical resistance. Thus, they are generally used as a soluble precursor polymer, which forms complexes with solvent molecules, and then finally converts to the corresponding polyimides via imidization reaction. This complexation with solvent has caused severe difficulty in the characterization of the precursor polymers. However, significant progress has recently been made on the detailed characterization of PI precursors and their imidization reaction. On the other hand, much research effort has been exerted to reduce the dielectric constant of PIs, as demanded in the microelectronics industry, through chemical modifications, as well as to develop high performance, light-emitting PIs and liquid crystal (LC) alignment layer PIs with both rubbing and rubbing-free processibility, which are desired in the flat-panel display industry. This article reviews this recent research progresses in characterizing PIs and their precursors and in developing low dielectric constant, light-emitting, and LC alignment layer PIs.