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Dive into the research topics where Hyeong Taek Ham is active.

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Featured researches published by Hyeong Taek Ham.


Polymer | 2003

Characteristics of polyvinylpyrrolidone-layered silicate nanocomposites prepared by attrition ball milling

Chong Min Koo; Hyeong Taek Ham; Min Ho Choi; Sang Ouk Kim; In Jae Chung

Polyvinylpyrrolidone (PVP)/sodium montmorillonite (MMT) nanocomposites prepared via the solution intercalation method were investigated by UV/vis, SEM, X-ray diffraction, TEM, FT-IR and PLM (polarized light microscopy). PVP/MMT nanocomposites show exfoliation below 20 wt% MMT and intercalation above this concentration. Nanocomposites retain good optical clarity and increased thermal resistance with MMT content. The compatibility between PVP and MMT and their enhanced properties may be explained by hydrogen bonding interactions. In addition, the nanocomposites prepared under more rigorous mixing conditions show better transparency because the smaller particle sizes are induced. In addition, the study on optically clear PVP/MMT suspensions helps one to understand how optical anisotropy of MMT is affected by the existence of polymer in aqueous solution.


Macromolecular Research | 2004

Chemical modification of carbon nanotubes and preparation of polystyrene/carbon nanotubes composites

Hyeong Taek Ham; Chong Min Koo; Sang Ouk Kim; Yeong Suk Choi; In Jae Chung

Single-walled carbon nanotubes (SWNTs) have been chemically modified through the formation of carboxylic acid functionalities or by grafting octadecylamine and polystyrene onto them. We purified SWNTs with nitric acid to remove some remaining catalysts and amorphous carbon materials. After purification, we broke the carbon nanotubes and shortened their lengths by using a 3∶1 mixture of concentrated sulfuric acid and nitric acid. During these purification and cutting processes, carboxylic acid units formed at the open ends of the SWNTs. Octadecylamine and amino-terminated polystyrene were grafted onto the cut SWNTs by condensation reactions between the amine and carboxylic acid units. The cut SWNTs did not disperse in organic solvents, but the octadecylaminegrafted and polystyrene-grafted SWNTs dispersed well in dichloromethane and aromatic solvents (e.g., benzene, toluene). Composites were prepared by mixing polystyrene with the octadecylamine-grafted or polystyrene-grafted SWNTs. Each composite had a higher dynamic storage modulus than that of a pristine polystyrene. The composites exhibited enhanced storage moduli, complex viscosities, and unusual non-terminal behavior when compared with a monodisperse polystyrene matrix because of the good dispersion of carbon nanotubes in the polystyrene matrix.


Journal of Colloid and Interface Science | 2005

An explanation of dispersion states of single-walled carbon nanotubes in solvents and aqueous surfactant solutions using solubility parameters.

Hyeong Taek Ham; Yeong Suk Choi; In Jae Chung


Polymer | 2005

Singlewall carbon nanotubes covered with polypyrrole nanoparticles by the miniemulsion polymerization

Hyeong Taek Ham; Yeong Suk Choi; Namjo Jeong; In Jae Chung


Macromolecules | 2002

Morphology Evolution and Anisotropic Phase Formation of the Maleated Polyethylene-Layered Silicate Nanocomposites

Chong Min Koo; Hyeong Taek Ham; Sang Ouk Kim; Ki Hyun Wang; In Jae Chung; Dae-Cheol Kim; Wang-Cheol Zin


Journal of Polymer Science Part A | 2006

Singlewall carbon nanotubes covered with polystyrene nanoparticles by in‐situ miniemulsion polymerization

Hyeong Taek Ham; Yeong Suk Choi; Mu Guen Chee; In Jae Chung


Polymer Engineering and Science | 2008

PEDOT-PSS/singlewall carbon nanotubes composites

Hyeong Taek Ham; Yeong Suk Choi; Mu Guen Chee; Myoung Hwan Cha; In Jae Chung


Polymer | 2003

Polymer/silicate nanocomposites synthesized with potassium persulfate at room temperature: polymerization mechanism, characterization, and mechanical properties of the nanocomposites

Yeong Suk Choi; Hyeong Taek Ham; In Jae Chung


Journal of Physical Chemistry B | 2006

Macroporous Polymer Thin Film Prepared from Temporarily Stabilized Water-in-Oil Emulsion

Hyeong Taek Ham; In Jae Chung; Yeong Suk Choi; Sun Hwa Lee; Sang Ouk Kim


Macromolecular Symposia | 2007

Fabrication of Ordered Porous SWNT-Polymer Nanocomposites by Emulsion Templating

Sun Hwa Lee; Hyeong Taek Ham; Ji Sun Park; In Jae Chung; Sang Ouk Kim

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Dae-Cheol Kim

Pohang University of Science and Technology

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Wang-Cheol Zin

Pohang University of Science and Technology

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