Experimental and theoretical XPS study of model molecules for poly(methyl methacrylate)

Abstract High‐resolution C is and O is gas‐phase X‐ray photoelectron spectra of methyl isobutyrate, methyl methacrylate, methyl acrylate, acrylic acid, acetic acid and formic acid have been investigated as model compounds for solid poly(methyl methacrylate) (PMMA). Secondary chemical shifts, variations in peak shapes and intensities for the different core lines were observed. It is shown that asymmetries and differences in line widths of the component peaks should be considered for a correct analysis of the solid polymer spectra. The observed intensities of the different C 1s and O is peaks in the gas‐phase spectra do not follow stoichiometric ratios owing to different shake‐off/shake‐up probabilities. The gas‐phase core electron binding energies have been compared with ab initio ΔSCF calculations where the relaxation of the core‐hole state was included. Using a group shift argument, the relationship between the gas‐phase model molecule shifts and the solid PMMA shifts have been discussed and applied to the analysis of the PMMA spectra.