Poly(carboxypyrrole)s That Depolymerize from Head to Tail in the Solid State in Response to Specific Applied Signals.

This Article describes the design, synthesis, and analysis of a new class of polymer that is capable of depolymerizing continuously, completely, and cleanly from head to tail when a detection unit on the head of the polymer is exposed to a specific applied signal. The backbone of this polymer consists of 1,3-disubstituted pyrroles and carboxy linkages similar to polyurethanes. Diverse side chains or reactive end-groups can be introduced readily, which provides modular design of polymer structure. The designed depolymerization mechanism proceeds through spontaneous release of carbon dioxide and azafulvene in response to a single triggering reaction with the detection unit. These poly(carboxypyrrole)s depolymerize readily in nonpolar environments, and even in the bulk as solid-state plastics.

Self-Immolative Poly(4,5-dichlorophthalaldehyde) and its Applications in Multi-Stimuli-Responsive Macroscopic Plastics.

End-capped poly(4,5-dichlorophthalaldehyde) (PCl2PA), which is a new self-immolative CD(r) polymer with the unique capability of depolymerizing continuously and completely in the solid state when an end cap is cleaved from the polymer by reaction with a specific molecular signal, is described. End-capped poly(4,5-dichlorophthalaldehyde) is sufficiently stable to enable patterning of three-dimensional macroscopic polymeric materials by selective laser sintering. These unique materials are capable of 1) autonomously amplifying macroscopic changes in the material in response to specific molecular inputs, and 2) altering their responses depending on the identity of the applied signal. Thus, not only does end-capped PCl2PA provide new and unique capabilities compared to the small subset of existing CD(r) polymers, but it also provides access to a new class of stimuli-responsive materials.

Use of catalytic fluoride under neutral conditions for cleaving silicon-oxygen bonds.

This Article describes the development of conditions for cleaving silicon-oxygen bonds using catalytic quantities of fluoride at neutral pH in mixed organic-aqueous solutions that contain buffer. A variety of silicon protecting groups can be removed under these conditions, which show tolerance for acid- and base-sensitive groups. A modified procedure also is presented using catalytic fluoride in anhydrous dimethyl sulfoxide-methanol, which generates primarily volatile silicon byproducts.

Continuous Head-to-Tail Depolymerization: An Emerging Concept for Imparting Amplified Responses to Stimuli-Responsive Materials.

Polymers that depolymerize continuously and completely from head-to-tail when a reaction-based detection unit is cleaved from the polymer provide both selective and amplified responses, a rare combination, to stimuli-responsive polymeric materials. This Viewpoint contextualizes this new class of depolymerizable polymers and outlines the key areas for growth and innovation.