Thermal decomposition of diethyl ketone triperoxide in methyl methacrylate: Theoretical and experimental study of the initial solvation state and its influence on the polymerization process

Abstract

The decomposition rate constant (kd) of diethyl ketone triperoxide (DEKTP, 3,3,6,6,9,9-hexaethyl-1,2,4,5,7,8-hexaoxacyclononane) in methyl methacrylate (MMA) was determined by the kinetic study of its thermal decomposition at temperatures from 110 to 140°C. The calculated kd for DEKTP in MMA was 2.4 times lower (at 130°C) compared with that previously determined and reported in styrene (St). Density functional theory (DFT) calculations demonstrated that the decomposition of DEKTP molecule in MMA required higher interaction energy than in St, thus explaining its lower kd value. Bulk polymerization kinetics of MMA using DEKTP as the initiator revealed the presence of an induction period, in contrast with St polymerization, providing clear evidence of the solvation state influence at early polymerization stages. This work provides mechanistic insights into the interactions among the multi-functional cyclic peroxide DEKTP and vinyl monomers; St and MMA, and their influence on the polymerization kinetics.