Cross-linked polymers are essential to many commercial applications where materials encounter harsh conditions, including elevated temperatures and corrosive chemicals. The high density of cross-links within these networks are responsible for providing materials with their enhanced properties; unfortunately, these same cross-links prevent degradation and recyclability. Cross-linked networks are difficult to degrade without the employment of harsh chemical, mechanical, or thermal treatments, which can result in environmental and safety issues. We have recently developed a series of silyl-triol containing poly(urethane) (Silyl-PU) networks that degrade under mild conditions with fluoride salt solutions. To understand how the thermomechanical properties of these networks influences the time of disassembly we have developed a series of silyl-based triols with different structure (i.e. extended vs. non-extended chains) and electrophilicity (i.e. phenyl silyl vs. methyl silyl). Herein, we describe the synthesis and characterization of these triols, the formation of cross-linked poly(urethane) networks with these polyols, the thermal properties of these networks, and their times of disassembly in various fluoride salt solutions. We further demonstrate that these poly(urethane) networks can be coated onto organic substrates and removed without damaging the underlying material. During the removal process the Silyl-PU breaks down into volatile molecules, cyclic oxazolidinones, and reusable hexamethylenediamine (HMDA). HMDA, a value-added molecule, can be isolated and reused for numerous applications.

Selectively removable thermosetting poly(urethane)s from extended chain silyl-triols

ACS Spring 2022

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