| Abstract
| - This manuscript describes the structure and wettability of self-assembled monolayers (SAMs) derivedfrom the adsorption of a series of ω-methoxyalkanethiols (CH3O(CH2)nSH, where n = 9−14) onto thesurface of gold. Using ellipsometry, polarization modulation infrared reflection absorption spectroscopy(PM-IRRAS), and contact angle measurements, the interfacial properties were examined as a function ofchain length. Analysis by ellipsometry revealed a progressive increase in the thickness of the films as thechain length of the adsorbate was increased. Similarly, analysis by PM-IRRAS revealed a progressiveincrease in the conformational order of the methylene chains of the films. Moreover, the frequency andintensity of two characteristic C−H stretching bands of the methoxy groups were observed to varysystematically as a function of odd- versus even-numbered chain length, reflecting an alternating structuralchange in the films (i.e., an “odd−even” effect). Studies of contact angle wettability revealed that themethoxy-terminated SAMs were more wettable than SAMs derived from the corresponding methyl-terminated alkanethiols (CH3(CH2)n+1SH), consistent with a substantial polar influence of the terminalether moiety. In addition, the contact angles were observed to increase with increasing chain length ofthe methoxy-terminated SAMs. Moreover, small but systematic variations in wettability as a function ofodd- versus even-numbered chain length were also observed; their origin was attributed to the influenceof surface dipoles.
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