Polymer with Competing Depolymerization Pathways: Chain Unzipping versus Chain Scission

Interest in triggered depolymerization is growing, driven by needs in sustainable plastics, self-healing materials, controlled release, and sensory amplification. For many triggered depolymerization reactions, the rate-limiting step does not directly involve the stimulus, and therefore, depolymerization kinetics exhibit only weak or no correlation to the concentration and reactivity of the stimulus. However, for many applications, a direct relationship between the stimulus and the depolymerization kinetics is desired. Here we designed, synthesized, and studied a polymer in which a nucleophile-induced chain scission (NICS) mechanism competes with the chain unzipping pathway. We find that the choice of the chain end functionality and the character of the nucleophile determines which of these is the predominant pathway. The NICS pathway was found to be dependent on the stimulus concentration, in contrast to the chain unzipping mechanism. We demonstrate transferability of these molecular-scale, structure-property relationships to nanoscale materials by formulating the polymers into host nanoparticles.