The Wetting of Monolayer Films Exposing Ionizable Acids and Basesl

This paper describes the wetting by water of monolayer fibns formed bythe spontaneous assemblyof fong-cfifr;1*anethioG, HS(CH;rJX, onto gold surfaces, w\e1e X = carboxylgJ,.e.$-o-sph93ate' 5-tetra?olo, f -iiiarroto, or 2-imidrioto. 'Mon6iayers weie also generated from mixtures of HS(CHdtd ald HS(CHs)ra CH" ffe wetting by water of the single-component and the mixed surfaces was examined as a function of pH. The surfaies-uniformly becam6 more wettable at values of pH at which the interfacial groups were chiiged. Surfaces rich in carboxylic acid groups exhibited gn unelpected behavior: the surfaces were less *.ttibl. at values ofpU between-3 and ? tfran at lower or higher valuts 9f pH. We attribute this unerpected behavior to conformational changes of the terminal parts of the chain including the carborylate groups