Controlled/living carbocationic polymerization

Matyjaszewski, K. and M. Sawamoto, Controlled/Living Carbocationic Polymerization, Chap. 4 in Cationic Polymerizations Mechanisms, Synthesis, and Applications, K. Matyjaszerski, ed., Marcel Dekker, New York, 1996. 

It is possible to work at either lower cation concentrations—but this could lead to stronger effects of impurities (adventitious moisture)—or to use more specialized flow reactors. The dynamic equilibration between active and dormant species offers another solution to this problem. In this case, the sensitivity to impurities is low due to the high total number of chains, but the momentary concentration of propagating carbocations is tremendously reduced. This approach is always used in new controlled/ living carbocationic polymerizations, as we will discuss in detail in this chapter. 

The new controlled/living carbocationic polymerizations were, in some sense, quite similar to new controlled/living anionic systems devel-... 

The mechanistic details and roles of all constituents of the multicomponent initiating systems for new controlled/living carbocationic polymerization are also discussed in Section VI. At this stage it suffices to say that in both the new systems and conventional carbocationic polymerization, monomer is consumed by the repetitive electrophilic addition of growing carbocations whether or not in dynamic equilibrium with either covalent species or onium ions. 

Table 1 Controlled/Living Carbocationic Polymerization The Status Quo for Monomers and Methods8...

Table 2 Nucleophiles for Controlled/Living Carbocationic Polymerization...

In previous sections we discussed the typical methodologies and practical aspects of the controlled/living carbocationic polymerizations of vinyl ethers, isobutene, styrene, and other monomers. It is possible to select optimal conditions such as the structure and concentrations of initiators, Lewis acids, additives (nucleophiles and salts), solvent, and temperature for each class of monomers in order to control and to prepare well-defined polymers. However, further progress requires a better understanding of the mechanisms of the involved reactions. 

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