Thiol-triggered deconstruction of bifunctional silyl ether terpolymers via an SNAr-triggered cascade

While Si-containing polymers can often be deconstructed using chemical triggers such as fluoride, acids, and bases, they are resistant to cleavage by mild reagents such as biological nucleophiles, thus limiting their end-of-life options and potential environmental degradability. Here, using ring-opening metathesis polymerization, we synthesize terpolymers of (1) a functional monomer (e.g., a polyethylene glycol macromonomer or dicyclopentadiene); (2) a monomer containing an electrophilic pentafluorophenyl (PFP) substituent; and (3) a cleavable monomer based on a bifunctional silyl ether . Exposing these polymers to thiols under basic conditions triggers a cascade of nucleophilic aromatic substitution (SNAr) at the PFP groups, which liberates fluoride ions, followed by cleavage of the backbone Si-O bonds, inducing polymer backbone deconstruction. This method is shown to be effective for deconstruction of polyethylene glycol (PEG) based graft terpolymers in organic or aqueous conditions as well as polydicyclopentadiene (pDCPD) thermosets, significantly expanding upon the versatility of bifunctional silyl ether based functional polymers.

Automated summary

Using ring-opening metathesis polymerization, terpolymers were synthesized consisting of a functional monomer, a monomer with an electrophilic pentafluorophenyl substituent, and a cleavable monomer based on bifunctional silyl ether. Exposing these polymers to thiols under basic conditions triggers nucleophilic aromatic substitution reactions, liberating fluoride ions and causing backbone deconstruction. This method effectively deconstructs polyethylene glycol-based graft terpolymers and polydicyclopentadiene thermosets, significantly expanding the versatility of bifunctional silyl ether-based functional polymers.