Metal-Free Living Cationic Polymerization via Carbon-Sulfur Bonds (2)

Abstract

This second review on novel metal-free cationic polymerizations is directed to living cationic polymerization that proceeds via reversible activation of carbon-sulfur bonds of thioethers via degenerative chain-transfer (DT) mechanism. In a similar way to cationic RAFT polymerization in the first review, a small amount of triflic acid generates the cationic propagating species, which interchanges with the thioether-dormant species via the sulfonium intermediate stabilized by the sulfur atom, to induce living cationic polymerization via the DT mechanism. This system can similarly control the molecular weight up to 1 10 5 with narrow molecular weight distributions (Mw/Mn < 1.2) and controlled chain-end groups in cationic polymerization of vinyl ethers and p-alkoxystyrene. The thioether-dormant species is highly stable and tolerant in comparison to the dormant species thus far reported in living cationic polymerization. This makes the obtained polymers applicable for subsequent post-polymerization reactions without any significant damages on the C-S bonds.