During living polymerization of isobutylene, marginal conditions can lead to reaction of carbenium ions with exo-olefin and production of coupled polyisobutylene (PIB). When living NB containing a coupled fraction is subjected to end-quenching with an alkoxybenzene compound in the presence of TiCl4, the coupling reaction is quantitatively reversed to form the two original chain ends, and the regenerated chains are observed to possess the desired alkoxyphenyl functionality. To demonstrate this phenomenon, various FIB samples were prepared to purposefully contain significant coupled fractions, from 10 to SS mol %, by quenching living FIB with hindered nucleophiles under marginal conditions. The coupled fractions were quantified by H-1 NMR and GPC. Coupled FIB samples were reacted with (3-bromopropoxy)benzene, methoxybenzene, or 4-phenoxy-1-butyl acrylate in the presence of TiCl4 and a source of protic catalyst. Various, protic sources were found to be effective including externally added water, adventitious protic sources, and any finite fraction of tert-chloride chain ends. Decoupling did not occur in the presence of a proton scavenger such as 2,6-lutidine. The resulting FIB samples were quantitatively or nearly quantitatively decoupled, as determined by H-1 NMR and GPC, and all of the chain ends visible by H-1 NMR possessed the desired alkoxyphenyl end groups. Other pi-nudeophile-type quenchers including N-methylpyrrole, 2-methylfuran, allyltrimethylsilane, and methallyltrimethylsilane were found to be ineffective under the same or similar conditions due apparently to reaction of the quencher with the necessary protic catalyst.