Simultaneous Tailoring of Surface Topography and Chemical Structure for Controlled Wettability

1. Simultaneous Tailoring of Surface Topography and Chemical Structure for Controlled Wettability Wei Chen, Mount Holyoke College, DMR 0209282 The proposed work on topographical control of wettability has been completed. We are currently studying the effect of chemical structure on wettability. Chemically homogeneous as well as gradient surfaces have been prepared. We take advantage of the versatile reactivity of -OH groups in poly(vinyl alcohol) (PVOH) that has been demonstrated in our earlier studies. PVOH surfaces were reacted with heptafluorobutyryl chloride (HFBC) in vapor phase. A maximum thickness increase of 46 Å was observed after reaction with HFBC. The location of HFBC source relative to PVOH-adsorbed samples and relative rates of HFBC diffusion across the samples and reaction with the samples are key factors for controlling surface geometries (0 to 46 Å gradual increase across the two dimensional surfaces) and functional group gradients. Using surface chemistry to control surface topography on the nanoscopic level is a new concept. The prepared samples have “gradient” properties due to variation in chemical structure along the gradient, for example, Au nanoparticles adsorb strongly to the PVOH end but do not adsorb at all to the HFBC end. X: functional group Fig 1. Gradient Surfaces. before after Fig 2. AFM images (500 x 500 nm) of PVOH (left) and HFBC (right) before and after 5 nm Au adsorption.

2. Simultaneous Tailoring of Surface Topography and Chemical Structure for Controlled Wettability Wei Chen, Mount Holyoke College, DMR 0209282 Education: • Under this grant, Linda Paradis ‘03 has completed her M.A. degree; Nui Takeshita’03, Mamle Quarmyne ‘03, Surangkhana Martwiset ‘03, Rose Ndong ‘05 have completed their B.A. degrees; Chantel Tester ‘07 and Angela Diciccio ‘08 are currently supported by this grant. • All the students who have been supported by the grant are female undergraduates and typically start independent research in their first or second years. They spend their summers full time and academic years part time (~15 h per wk) doing research and have been exceptionally productive - three articles have resulted from research supported by this grant and one more is under preparation. -Takeshita, N.; Paradis, L. A.; Chen, W. Langmuir, 2004, 20, 8131. - Kozlov, M.; Quarmyne, M.; Chen, W.; McCarthy, T. J. Macromolecules 2003, 36, 6054. -Quarmyne, M.; Chen, W. Langmuir 2003, 19, 2533. Human Resources/Outreach: • Minority students are particularly encouraged to participate in research. Three out of seven students supported by this grant are minorities. • Served on a panel to encourage graduate students consider teaching/doing research at four-year undergraduate institutes. • Taught a polymer tutorial to a group of middle and high school chemistry teachers. Research group picture 2005