Emulsion Polymerization of 2-Methylene-1,3-Dioxepane and Vinyl Acetate: Process Analysis and Characterization

The development of polymerization methods that installweak linksor degradable bonds in the backbone of otherwise all-carbon chainscould accelerate the design and commercialization of new classes ofrecyclable, upcyclable, or biodegradable polymers. Cyclic ketene acetalsincluding widely studied 2-methylene-1,3-dioxepane (MDO) can be usedas comonomers in conventional free-radical polymerizations to insertlabile ester bonds into addition polymer backbones. However, the keyobstacle in deploying MDO in water-borne, industrially relevant processesis hydrolysis of the monomer itself. Optimized conditions includingrelatively low temperatures, mildly alkaline pH, and consistent radicalflux lead to high in-process conversions, a rapid rate of polymerization,and a low degree of MDO hydrolysis. Although MDO hydrolysis competesstrongly with copolymerization, degradation can be minimized duringaqueous emulsion polymerization with vinyl acetate to give robustincorporations of & SIM;90% MDO. The methods and quantitative analysistools reported here provide principles for the copolymerization ofMDO in aqueous media and will drive innovations in the circular polymereconomy.