MALDI SpiralTOF high‐resolution mass spectrometry and Kendrick mass defect analysis applied to the characterization of poly(ethylene‐co‐vinyl acetate) copolymers

RATIONALE Poly(ethylene-co-vinyl acetate) copolymers - usually referred to as EVA - are first class industrial polymers used for applications ranging from padding to photovoltaics as encapsulant for the silicon solar cells. Various techniques have been used for their characterization but the analysis of intact EVA chains using mass spectrometry (MS) has not been reported so far. METHODS Three copolymers containing 18, 25 and 40 wt% vinyl acetate (VA) have been characterized using an off-line coupling of size-exclusion chromatography (SEC) and matrix-assisted laser desorption/ionization (MALDI) spiral-time-of-flight (TOF) high-resolution mass spectrometry (HRMS). The representativeness of those results for the entire samples has been checked using (13) C NMR spectroscopy. Lastly, Kendrick mass defect analysis has been proposed as an alternative and user-friendly data treatment method. RESULTS The shortest chains isolated by SEC fractionation and mass-analyzed by HRMS have been thoroughly described in terms of end-groups (found to be hydrogens) and co-monomeric composition. The VA content was successfully derived from the peak assignments in MS spectra for the EVA 40 wt% and 25 wt% while it tended to be overestimated for the latest EVA 18 wt% (increasing poly(ethylene) character). Similar results have been found using a faster data treatment method relying on the Kendrick mass defect analysis of the MS data. CONCLUSIONS EVA low molecular weight intact oligomers have been extensively characterized by MS for the first time and the structural features confidently extended to the full sample according to NMR data. The Kendrick mass analysis finally constituted an efficient method for a fast evaluation of their VA content with no need for manual assignment. © 2016 The Authors. Rapid Communications in Mass Spectrometry Published by John Wiley & Sons Ltd.