Infinite lifetimes in radical polymerization

We study radical polymerization dynamics. Our theory explains "infinite" living chain radical lifetimes in experiments where steady state is interrupted by switching off radical production. Short (unentangled) living chains grow to become long (entangled) or are terminated through interpolymeric radical-radical reactions. The net termination rate, dominated by short-long reactions in steady state, then drops so sharply that the living population never decays. Consistent with experiment, we find the number of terminated chains grows as t(1/2) during the transient when shorter chains disappear.