Sequence distribution of poly(ether‐sulfone)/poly(ether‐ketone) copolymers by mass spectrometry and ¹³C NMR

The sequence distributions of four poly(ether‐sulfone)/poly(ether‐ketone) (PES/PEK) copolymer samples were determined by means of fast atom bombardment mass spectrometry (FAB‐MS) and by 13 C NMR spectroscopy. The controlled partial degradation of the copolymer chains to produce oligomers suitable of FAB‐MS analysis was performed with sodium methoxide in dimethyl sulfoxide solution at 130°C, and the experimental conditions were optimized. The sequential arrangements of ether‐sulfone/ether‐ketone units present in these materials were estimated by a best‐fit minimization method using the MACO4 computer program which compares the experimental FAB‐MS spectral intensities with theoretical intensities. Random PES/PEK copolymer samples showed quite the same sequence arrangements as expected from monomer feed‐ratios used in the syntheses. Instead, a PES/PEK copolymer sample expected to be exactly alternating (from the synthesis procedure) showed 44% of random sequences owing to the transetherification reaction which occurred in the synthesis. The results of sequential analysis obtained from 13 C NMR data compare well with the data obtained by the FAB‐MS analysis.