Hyeong Taek Ham
KAIST
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Featured researches published by Hyeong Taek Ham.
Polymer | 2003
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
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
Hyeong Taek Ham; Yeong Suk Choi; In Jae Chung
Polymer | 2005
Hyeong Taek Ham; Yeong Suk Choi; Namjo Jeong; In Jae Chung
Macromolecules | 2002
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
Hyeong Taek Ham; Yeong Suk Choi; Mu Guen Chee; In Jae Chung
Polymer Engineering and Science | 2008
Hyeong Taek Ham; Yeong Suk Choi; Mu Guen Chee; Myoung Hwan Cha; In Jae Chung
Polymer | 2003
Yeong Suk Choi; Hyeong Taek Ham; In Jae Chung
Journal of Physical Chemistry B | 2006
Hyeong Taek Ham; In Jae Chung; Yeong Suk Choi; Sun Hwa Lee; Sang Ouk Kim
Macromolecular Symposia | 2007
Sun Hwa Lee; Hyeong Taek Ham; Ji Sun Park; In Jae Chung; Sang Ouk Kim