Specific Living Cationic Polymerization Systems

Stronger Lewis acids such as SnCL, TiCL, and CH3AICI2 yield fast but uncontrolled polymerization with broad PDI. LCP of vinyl ethers can he achieved if the other components and reaction parameters are appropriately adjusted hy various combinations of lower reaction temperature, added nucleophile, added common salt, and solvent prolarity. For example, polymerization of isobutyl vinyl ether using HCl as the initiator (or one can use the preformed adduct of monomer and HCl) with SnCLj or TlCLi in CH2CI2 is non-LCP 

The formation of Poisson distributions is corroboration of the fast equilibrium assumed between active and inactive propagating centers. For any propagating center, the fractions of its total lifetime spent as active and inactive centers are very close to those for other propagating centers. 

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The synthesis of functional or stimuli-responsive polymers in cationic polymerization often suffered due to the difficulty of polymerizing polar monomers with basic side groups. Therefore, beginning a couple of years ago, a re-examination of initiating systems was conducted. This chapter focuses on recent developments in living cationic polymerization systems, specifically the base-stabilized version. For other living cationic systems, excellent reviews are available elsewhere [215,241-246]. 

In light of the knowledge currently available, this chapter aims to discuss the general principles, methodologies, and scope of controlled/ living cationic polymerizations and more specific examples for representative classes of monomers. The next chapter will be devoted to the controlled syntheses of new functional polymers using these systems. 

This paper discusses (i) the principles of living cationic polymerization, (ii) new initiating systems for living polymerization of vinyl ethers, which are based on phosphate esters as initiators, and (iii) some selected topics in the controlled polymer syntheses by our living cationic processes, specifically focused on end-functionalized polymers and star-shaped or multi-armed macromolecules. 

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