ABSTRACT
As discussed in Chapter 4, it is now possible to design and carry out controlled cationic polymerizations for almost all classes of cationically polymerizable vinyl/alkene monomers using a wide variety of initiating systems. In these modern systems, in sharp contrast to the conventional cationic polymerizations, the molecular weights and the molecular weight distributions of the polymers, as required for living polymerizations, can be precisely controlled, which demonstrates the suppression of chain transfer, termination, and other undesirable side-reactions that have been believed extremely difficult to eliminate in the conventional acid-catalyzed or carbocationic polymerizations. As already seen, there is still a contro versy about whether some of cationic polymerization is “ living” or “ con trolled.” Throughout this chapter, for simplicity, however, we use the term “ living” for the polymerizations that might be considered as “ con trolled” in the sense that has already been discussed in the preceding chapters. The development of such a new generation of cationic polymer izations in the 1980s and 1990s, whatever its mechanistic implications might be (see Chapter 4), has in turn opened a new vistas o f polymer syntheses via cationic processes in which the precise control of polymer architectures is feasible [1-3].
