Near-edge X-ray absorption fine structure spectroscopy on ordered films ofan amphiphilic derivate of 2,5-diphenyl-1,3,4-oxadiazole

The surfaces of ordered films formed from an amphiphilic derivative of 2,5- diphenyl-1,3,4-oxadiazole by the Langmuir-Blodgett (LB) technique and organ ic molecular beam deposition (OMBD) were investigated by the use of near-ed ge X-ray absorption fine structure (NEXAFS) spectroscopy. For the assignmen t of the spectral features of the C, N, and O K-edge absorption spectra, fi ngerprint spectra of poly(p-phenylene terephthalamide) (Kevlar), poly(ethyl ene terephthalate), poly(p-phenylene-1,3,1-oxadiazole), and 2,5-di(pentadec yl)-1,3,4-oxadiazole, which contain related chemical moieties, were recorde d. Ab initio molecular orbital calculations, performed with explicit treatm ent of the core hole, are used to support the spectral interpretations. Ang le-resolved NEXAFS spectroscopy at the C, N, and O K-edges suggests a prefe rentially upright orientation of the oxadiazole derivative in the outermost layer of the films. X-ray specular reflectivity data and molecular modelin g results suggest a similar interpretation.