Kinetic Study of Solution Radical Ring-Opening Polymerization of 2-Methylene-1,3-Dioxepane: Experiment and Modeling

Radical ring-opening polymerization (rROP) of cyclic ketene acetals (CKAs) (e.g., 2-methylene-1,3-dioxepane, MDO) provides an attractive route to incorporate degradable groups into all-carbon backbone polymers. However, the study of solution polymerization kinetics of rROP remains limited. In this work, the solution rROP kinetics of MDO are systematically investigated through a combination of experimental and kinetic modeling approaches. The polymerizations of MDO in different solvents, initial initiator concentrations, and monomer concentrations are examined. Based on the experimental and simulation results, the optimal conditions were identified. Subsequently, the effect of the reaction temperature on polymerization kinetics is investigated. Kinetic experiments performed at different temperatures are combined with a moment-based kinetic model to re-evaluate key kinetic parameters by least-squares optimization, resulting in a kinetic model capable of predicting rROP behaviors of MDO under varying conditions. Furthermore, by accounting for both ring-opening and ring-retaining propagation, the modeling framework is extended to CKA monomers with different ring sizes and structures to estimate the ring-opening selectivity of these CKA monomers.