Sequence-determined bottlebrush polymers are precisely, efficiently and conveniently synthesized.

Reported is an intriguing advance in living anionic polymerization (LAP) by a"locked-unlocked" mechanism in which the living anionic species can be quantitatively locked by end-capping with 1-(tri-isopropoxymethylsilylphenyl)-1-phenylethylene (DPE-Si(O-iPr) 3 )and can be unlocked by adding the key,s odium 2,3-dimethylpentan-3-olate (NaODP). These new insights into this mechanismw ere carefully confirmed by designing reactions involving sequential feeding of quantitative DPE-Si(O-iPr) 3 and traditional monomers mixed with NaODP,a nd subsequently characterizing the corresponding samples,taken during the feeding process,byGPC,NMR, and MALDI-TOF-MS techniques.T he switch from the locked to unlocked state was clearly confirmed by these characterization techniques.T he putative locked-unlockedm echanism in the LAP was simulated by the Gaussian method. This intriguing mechanistic finding of LAP reactions is expected to supplement the existing knowledge and facilitate the tailoring of specific structures for these polymerizations.