Surface Modification of Nanoporous Glass by Vapor Phase Deposition of Trifunctional Silanes

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Tom Fronk, Ling Liu, David Britt


The goal of this study is the surface modification of nanoporous glass with trifunctional silanes to obtain highly hydrophobic porous material for application as a nano energy absorption system (NEAS). Alkyl- and fluoro-silanes were deposited from vapor onto nanoporous glass (Millipore Controlled Pore Glass (CPG), 50 nm nominal pore diameters). All samples were rendered hydrophobic (142-147). Silane surface coverage was determined from XPS survey spectra and BET and TGA methods. These methods revealed octadecyltrichlorosilane (C18) formed multilayers (256% surface coverage) on CPG, leading to complete blockage of the nanopores as confirmed with SEM. Alky-silanes with 3 and 6 carbon tails yielded surface coverage values of 21% and 29%, respectively, whereas a 3-carbon trifluorosilane yielded 56% surface coverage. Additionally, fluorosilane modified CPG has almost no blockage of pores and the highest surface area after silanization, making it the most promising candidate for rendering nanoporous glass hydrophobic for NEAS applications.

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