Polymer with Competing Depolymerization Pathways: Chain Unzipping versus Chain Scission

Abstract

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.

Thermal Aging Rheological Behavior of Magnetorheological Elastomers Based on Silicone Rubber

“…This kind of phenomenon might be due to the decrement of cross-linking density that is related to the chain scission in the network at a high temperature. The formation of the chain scission might be attributed to a constitution of linear molecules in the network, which led to the slipping of matrix-matrix and particles-particles in the amorphous regions [28]. Meanwhile, a steady state occurred at one point in between 0.39 and 0.58 T of the magnetic field, where the magnetization of the magnetic particles and local field strength were at equilibrium.…”

Green self-immolative polymer: molecular antenna to collect and propagate the signal for zymogen activation

“…Noteworthy, to our knowledge, there is only one, very recent prior example of a polymer that can degrade by two mechanisms, main chain scission or self-immolation, and kinetics of the latter process was measured in hours. 36 Uniquely, depolymerization of LA PDS was rapid and complete within minutes (Figure 1F), and initiation could occur at any disulfide bond in the backbone, not necessarily at the chain end, as is most typical for other SIP systems. [4][5] The zymogen design was first performed for a cysteinyl protease papain.…”

Unifying Step-Growth Polymerization and On-Demand Cascade Ring-Closure Depolymerization via Polymer Skeletal Editing

“…The chemical foundations to design PCs by step-growth polymerization with ring-closing degradative ability imposes the utilization of monomers with adequate ethylene or propylene spacers between the reactive groups but also processing conditions and adequate ceiling temperature that favor their enchainment into polymers instead of a cyclic scaffold formation. Self-immolative polymers represent an elegant solution to this issue as they can be delivered by step-growth polymerization while being prone to spontaneous disassembly via a domino fashion upon removal of a triggering moiety by an appropriate stimulus. − While interesting but rarely illustrated with polycarbonates, this class of materials suffers from (1) the utilization of protected monomers, generally not easily accessible and not sustainable, and/or (2) the stabilization of the growing chains by fast trapping of the reactive terminus to prevent a reversion, thus limiting the molar mass to short chains, which is detrimental for the thermomechanical performances of the materials …”

“…42−54 While interesting but rarely illustrated with polycarbonates, this class of materials suffers from (1) the utilization of protected monomers, generally not easily accessible and not sustainable, and/or (2) the stabilization of the growing chains by fast trapping of the reactive terminus to prevent a reversion, thus limiting the molar mass to short chains, which is detrimental for the thermomechanical performances of the materials. 55 Herein, we report an original and facile methodology to fabricate polycarbonate-type polymers with cascade ringclosing depolymerization ability via an activated chain-end mechanism, delivering new cyclic scaffolds upon deconstruction. Capitalizing on our recent approach of furnishing regioregular polycarbonates by room-temperature step-growth copolymerization of exovinylene biscyclic carbonates and diols, 56−58 copolymerization and ring-closing depolymerization.…”