In this issue of Cell Reports Physical Science, Pan and co-workers synthesize alkylcatecholboranes that can be oxidized by oxygen to drive the release of carbon-centered radicals for initiating reversible addition-fragmentation chain transfer (RAFT) polymerization. These organoboranes can slowly decompose to radicals that enable RAFT polymerization with exceptional control yielding ultra-high molecular weight (UHMW) polymers.