Quasi-living cationic polymerization

The synthesis of A2B miktoarm star polymers has been discussed and exemplified using PIB as a component. The synthesis involves a quasi living cationic polymerization of isobutylene from a monofunctional cationic initiator. This initiator also contains a blocked hydroxyl group. Eventually, the blocked hydroxyl group of the initiator is deblocked, and functionalized with a branching agent. This activated reagent is then used for an atom transfer radical polymerization process of /erf-butyl acrylate (18). 

The INBFER technique has been used for quasi living cationic polymerization of isobutylene. Bi- and tnfunctional initiators yield telechelics with two or three chlorine end groups (Scheme 6). ... 

Since the metal alkyl is only involved in initiation of chain growth while subsequent propagation and chain transfer (usually involving chain transfer to monomer via hydride abstraction ) are usually very rapid, it is generally not possible to determine the fate of the metal alkyl in such polymerizations. End-group analyses provide evidence for a cationic propagation and chain-transfer mechanism, but the initiator moiety is not detected unless the process is at least quasi-living under the conditions studied. 

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