Near-edge X-ray absorption fine structure (NEXAFS) measurements were performed on self-assembled monolayers (SAMs) of oligo(ethylene glycol) (OEG)-terminated alkanethiols adsorbed on gold. Films with a varying number of EG units were investigated. By comparing the experimental results with predictions for an “ideal film structure”, the degree of conformational orientation can be determined. Our results are consistent with earlier findings that the ethylene glycol units adopt a mixture of helical and amorphous conformations and allow it to quantify the maximum possible fraction of shorter oligomers displaying the helical conformation. The experiments were performed under high-vacuum conditions, thereby eliminating the effects of water on the conformation of the EG units. A significant amount of molecules in the films displays amorphous conformations.

Titanium oxide surfaces were coated with methyl-and hydroxyl-terminated dodecyl phosphate monolayers by immersion of the substrates into aqueous solutions of the corresponding ammonium salts (DDPO4-(NH4)2 and OH-DDPO4(NH4)2). The samples were examined by contact-angle measurements and nearedge X-ray absorption fine structure spectroscopy. DDPO4 was found to form self-assembled films of comparable quality to those of the longer octadecyl phosphate prepared from an organic solvent and to those of a similar thiol/gold system. The hydroxyl-terminated adsorbates, however, established films with a much lower degree of orientation under the same preparation conditions and showed "high" water contact angle values (50-55°) for a hydrophilic surface. Mixed films of both species establish a degree of orientation between those of both pure films, which is also reflected by their wettability.

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