Mechanical Acceleration of Ester Bond Hydrolysis in Polymers

Polymers containing ester bonds are ubiquitous. Often, these materials are mechanically challenged, which impacts their stability and degradation. While the accelerative effect of force on the degradation of polyester polymers is well recognized, little is known about the identity of the bonds that are cleaved, the nature of the cleavage reactions, and the force sensitivity of these processes. To provide molecular-level insights into the force-accelerated degradation of ester bonds, this study has investigated the degradation of ester bond-containing polymers in dilute solution ultrasonication experiments. These experiments revealed that chain degradation proceeds via concomitant homolytic carbon–carbon scission as well as ester bond hydrolysis, and demonstrated that ester bond hydrolysis is force accelerated, both under neutral and basic conditions. Experiments with side chain ester functional polymers, in contrast, did not indicate ester bond hydrolysis, which suggests that the molecular force does not lead to the activation of ester bonds that are orthogonal to the polymer backbone.