Organocatalytic and Chemoselective Polymerization of Multivinyl-Functionalized γ‑Butyrolactones

• Published in: ACS macro letters 2016-06, Vol.5 (6), p.772-776
• Main Authors: Gowda, Ravikumar R, Chen, Eugene Y.-X
• Format: Article
• Language: English
• ISSN: 2161-1653; 2161-1653
• DOI: 10.1021/acsmacrolett.6b00370

Achieving complete chemoselectivity in the polymerization of multivinyl polar monomers is an important yet challenging task, currently achievable only by metal- or metalloid-mediated polymerization processes but in a noncatalytic fashion. Now this work shows that organic N-heterocyclic carbene (NHC) catalysts effect rapid, chemoselective, and catalytic polymerization of multivinyl-functionalized γ-butyrolactones, particularly γ-vinyl-α-methylene-γ-butyrolactone (VMBL). Thus, the NHC-catalyzed polymerization of VMBL not only is quantitatively chemoselective, proceeding exclusively via polyaddition across the conjugated α-methylene double bond while leaving the γ-vinyl double bond intact, but also requires only an exceptionally low catalyst loading of 50 ppm, thus, exhibiting a remarkably high catalyst turnover frequency of 80000 h–1 and producing on average 33.6 polymer chains of M n = 73.8 kg/mol per NHC molecule. The resulting PVMBL can be either thermally cured into cross-linked materials or postfunctionalized with the thiol–ene “click” reaction to achieve complete conversion of the pendant vinyl group on every repeat unit into the corresponding thioether.