Functional end groups for polymers prepared using ring-opening metathesis polymerization

The precise placement of functional groups on the chain-ends of macromolecules is a major focus of polymer research. Most common living polymerization techniques offer specific methods of end-functionalization governed by the active propagating species and the kinetics of the polymerization reaction. Ring-opening metathesis polymerization has established itself as one of the most functional-group-tolerant living polymerization techniques known, but this tolerance has limited the number of available functionalization reactions. Metathesis chemists have therefore been required to develop a variety of end-functionalizations, adapting each of them to the reactivity scheme of the particular catalysts used and the complexity of the group to be attached. This review presents an overview of the methods developed for different types and generations of metathesis catalysts that are typically used in such polymerizations. We also present a 'field guide' of functionalization methods highlighting the factors to be considered when choosing the most appropriate approach.