Azo-Derived Symmetrical Trithiocarbonate for Unprecedented RAFT Control.

Bis(2-cyanopropan-2-yl)trithiocarbonate () is a new symmetrical trithiocarbonate with the best leaving group ever reported for reversible addition-fragmentation chain transfer (RAFT) polymerization. We propose an elegant route to obtain starting from 2,2'-azobis(2-methylpropionitrile) (AIBN) as a donor of the 2-cyanopropan-2-yl group. allowed the preparation of a high-molar-mass ( ≈ 135 kg mol) methyl methacrylate--butyl acrylate-methyl methacrylate triblock copolymer with unprecedented control ( = 1.04) in reversible-deactivation radical polymerization. Rheology measurements of this triblock copolymer showed a typical thermoplastic elastomer behavior with a steady rubbery plateau up to 120 °C.