COLL 91 |
| Gabor A. Somorjai, Aric Opdahl, Telly Koffas, and Joonyeong Kim. Department of Chemistry, Lawrence Berkeley National Laboratory and University of California, Berkeley, Berkeley, CA 94720 |
| Using sum frequency generation surface vibrational spectroscopy, polypropylene and polystyrene surfaces as well as polypropylene-polyethylene co-polymer surfaces have been studied in the presence of air or water. The hydrophobic CH3 groups, in the case of polypropylene, and phenyl groups in the case of polystyrene, are nearly perpendicular to the surface in air. However, in the presence of liquid these groups change orientation and become partially disordered. Amphiphilic molecules such as methanon and CH3CN order at polymer interfaces which is directly observable by SFG. Poly-HEMA hydrogel surfaces show changes of surface structure with increasing humidity. In the presence of water the surface is covered by carboxyl groups, but when dry methyl groups are covering the surface. When humidity changes the surface composition changes accordingly. Proteins, BSA, lysozyme and fibrinogen have been adsorbed on polystyrene surfaces. In the CH spectral range the ordering of these proteins are detectable. The phenyl group of polystyrene becomes disordered in the presence of adsorbed lysozyme while the other proteins, BSA and fibrinogen, have no effect on the orientation of the phenyl group of polystyrene. SFG surface vibrational spectroscopy has been extremely successful and useful to study the buried interfaces polymer-air and polymer-liquid under a variety of conditions and for studies of the structure of adsorbed molecules at these buried interfaces. |
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Vibrational Analyses of Dry and Wet Surfaces
8:30 AM-11:30 AM, Monday, March 29, 2004 Marriott -- Grand Ballroom H, Oral
Division of Colloid and Surface Chemistry |