New Polymers Survive a Loss of Protection

JACS Spotlights, Feb. 9, 2022 Sulfur-containing organic molecules called thiols and thiocatechols are used in a variety of reactions involving the formation of disulfide bonds, coupling to double and triple bonds, and attachments to metal surfaces. In contrast, their polymer counterparts, thiophenol-pendant and dithiocatechol-pendant polymers, tend to oxidize and form disulfide-cross-linked networks. This renders them insoluble in organic solvents, which in turn limits their practical application. Catechol-pendant polymers, their oxygen-containing counterparts, oxidize much slower, and they readily form coatings, adhesives, and self-healing materials. Jincai Li, Joseph Richardson, and Hirotaka Ejima recently reported the use of a protection–deprotection strategy that enabled them to synthesize the thiophenol-pendant polymer poly(4-thiostyrene), as well as the first synthesis of a dithiocatechol-pendant polymer─poly(3,4-dithiostyrene)─and the copolymer poly(3,4-dithiostyrene-co-styrene) (DOI: 10.1021/jacs.1c11479).

Unlike former efforts at protection–deprotection synthesis, the deprotection conditions used by Ejima’s group prevented undesirable cross-linking of the dithiocatechol moieties, resulting in polymers that are soluble in THF, DMF, and other common organic solvents. The polymers are amenable to full analysis using standard spectroscopic methods (FTIR, NMR, Raman, and MALDI-TOF-MS), another first for this class of compounds. This synthesis method can be adapted for reversible addition–fragmentation chain transfer (RAFT) polymerization, which suggests that other synthetic routes could use the new strategy as well.

Photo: Fabrizio Crisafio/Flickr, CC BY-NC 2.0

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