Enhancing the incorporation of 2-methylen-1,3-dioxepane (MDO) into industrial monomers by the addition of crotonate comonomers

Environmental concerns are pushing towards more sustainable materials such as degradable or bio-based polymers. 2-methylen-1,3-dioxepane (MDO) is a cyclic ketene acetal monomer that when reacts by radical ring opening polymerization can introduce degradable ester groups in the polymer backbone, but it is generally challenging to incorporate it uniformly with other industrially relevant vinylic monomers such as styrenics, methacrylics, acrylics and vinylics. In this work, we explore the use of butyl crotonate as termonomer to enhance the incorporation of MDO into common industrial monomers taking advantage of the particular reactivities of MDO and crotonate. Styrene is found not suitable for terpolymerization, as it just homopolymerized. With methyl methacrylate, the incorporation of MDO is substantially enhanced due to the presence of BCr, but the terpolymer is not homogeneous, and MDO is primarily incorporated in the closed form, which only partially enhanced the degradability. In the terpolymerization with ethyl acrylate high MDO incorporation is achieved (up to 80 %) and most of it is incorporated in to the open formed (80 %). Therefore, the obtained terpolymer shows complete degradation in 28 days. Last, the terpolymerization of vinyl acetate is the most successful, as almost total conversion of all monomers is achieved in short times, including (100 % conversion of MDO). Furthermore, the obtained terpolymers are highly homogeneous and degraded completely in few hours. The addition of crotonate monomer in formulations where MDO or other cyclic ketene acetal could bring new insights as it is shown that not only the incorporation of cyclic ketene acetals is enhanced but also that it favors the incorporation into the open form, which substantially enhanced the degradability of common polymers produced by radical polymerization.