COLL 262 |
| Kohei Uosaki, Rie Yamamoto, and Satoshi Nihonyanagi. Physical Chemistry Laboratory, Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo, 060-0810, Japan |
| Interfacial structures of alkylated polyvinylpyridine (Cn-PVP) brushes with various side chain lengths (n=0, 2, 6, 12) in dry nitrogen, water vapor, liquid water, and aqueous electrolyte solution were investigated by means of sum frequency generation spectroscopy. (SFG) spectra of the polymer brushes in the CH stretching region in dry N2 revealed that the conformational order of the side chain depended on the chain length. The highest conformational order was observed at the polymer brush with hexyl, C6, side chain, which was almost in all-trans conformation with its methyl group nearly perpendicular to the surface. Significant contribution from methylene CH vibration was observed in the SFG spectra of the polymer brush with the shorter, ethyl, C2, or longer, decyl, C12, side chains, reflecting less ordered structure. Higher degree of gauche defects were observed at all the brushes in contact with water vapor than in dry N2. Essentially no CH stretching peaks were observed in contact with liquid water, showing almost completely disordered structure. These conformation changes were very fast, suggesting that the changes were related to the orientation change of the side chains. SFG spectra of the brush/water interface in the OH stretching region were dominated by OH stretching vibration of ice-like water. The higher the electrolyte concentration, the lower the OH intensity, reflecting the reduction of the double layer thickness in the higher electrolyte concentration. |
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Vibrational Analyses of Dry and Wet Surfaces
6:00 PM-8:00 PM, Monday, March 29, 2004 Disneyland -- North Exhibit Hall, Poster
Division of Colloid and Surface Chemistry |