Thiol-triggered deconstruction of bifunctional silyl ether terpolymers an SAr-triggered cascade

• Published in: Chemical science (Cambridge) 2023-08, Vol.14 (33), p.8869-8877
• Main Authors: Brown, Christopher M, Husted, Keith E. L, Wang, Yuyan, Kilgallon, Landon J, Shieh, Peyton, Zafar, Hadiqa, Lundberg, David J, Johnson, Jeremiah A
• Format: Article
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/d3sc02868b

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 (S N Ar) 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. Thiol-induced nucleophilic aromatic substitution of pentafluorophenyl sidechains is introduced as a strategy for the mild deconstruction of bifunctional silyl ether-containing soluble polymers and crosslinked "thermoset" plastics.