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.