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

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Abstract
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 13C 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 13C NMR data compare well with the data obtained by the FAB‐MS analysis.

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