Emulsion copolymerization of 2-methylene-1,3-dioxepane (MDO) and acrylate monomers: Incorporation vs hydrolysis

Abstract

The incorporation of polyester moieties to the backbone of waterborne polymer dispersions by the emulsion copolymerization of 2-methylene-1,3-dioxepane (MDO) and acrylate monomers (n-butyl acrylate and 2-octyl acrylate) is explored in this work. Due to the competition between the consumption of MDO by hydrolysis (MDO is very sensitive to water) and by copolymerization reactions, seeded semibatch emulsion copolymerizations were carried out varying the temperature of the reaction, the feeding rates of the comonomers, and maintaining a basic pH (∼pH = 8) that decreases notably the rate of hydrolysis of the MDO. Interestingly, we found that the lower the temperature of the reaction (T = 20 °C) and the higher the monomer addition flow rate, allowed the highest incorporation of MDO in the copolymer (up to 86 mol %). Unfortunately, the MDO incorporated in the closed formed (i.e., in the acetal form) and therefore, the acrylate copolymers produced did not contain ester groups in the backbone. Furthermore, increasing the MDO composition in the copolymers under the same polymerization conditions favored more hydrolysis than copolymerization and hence, incorporation content decreased. On the other hand, the ester size (2-octyl vs n-butyl) of the acrylate did not have any noticeable effect in the MDO incorporation content.