In situ ATR-IR enabled kinetic modeling of ethylene/maleic anhydride copolymerization at elevated pressure

Mechanistic understanding of polymerization kinetics at elevated pressure requires quantitative, time-resolved access to reaction dynamics. Herein, we developed an integrated framework coupling in situ high-pressure ATR-IR spectroscopy with a kinetic model based on the method of moments. Using ethylene/maleic anhydride (E (1)/MAH (2)) copolymerization as a benchmark, this platform enabled real-time quantification of monomer consumption and in situ determination of copolymer composition, directly confirming strict alternating incorporation. The kinetic model showed excellent agreement with experiments, with deviations below 10%. Analysis revealed the cross-propagation of MAH to ethylene-terminated radicals ( k 12 ≈ 5.62 × 10 3 L mol −1 s −1 ) is over an order of magnitude faster than the reciprocal step ( k 21 ≈ 3.92 × 10 2 L mol −1 s −1 ), identifying the latter as rate-determining. Extrapolation of the model guided the precise synthesis of a high-molecular-weight copolymer ( M w = 107 kDa). This work establishes a generalizable in situ platform for elucidating kinetics in complex polymerization systems at elevated pressure.