Number and b GPC distributions for three polymers each with

Quirk and Lee concluded there is no single criterion which is satisfactory for determination of whether a given polymerization is living or not, Most of the radical polymerizations discussed in this chapter meet one or more of these criteria. 

The kinetics and mechanism of living radical polymerization have been reviewed by Fischer, Fukuda et a(. and Goto and Fukuda. In eonventional radical polymerization, new chains are continually formed through initiation while existing chains are destroyed by radical-radical termination. The steady state concentration of propagating radicals is -lO M and an individual chain will have a lifetime of only 1-10 s before termination within a total reaction lime that is 

It is not necessary that living radical polymerizations be slow. However, it follows from the above discussion that, for a high fraction of living chains, either the final degree of polymerization must be significantly lower than that in an otherwise similar conventional process or that conditions must be chosen such that the rate of polymerization is substantially lower. 

Heterogeneous polymerization processes (emulsion, miniemulsion, non-aqueous dispersion) offer another possibility for reducing the rate of termination through w hat arc known as compartmcntalization effects. In emulsion polymerization, it is believed that the mechanism for chain stoppage within the particles is not radical-radical termination but transfer to monomer (Section 

These possibilities have provided impetus for the development of living heterogeneous polymerization (Sections 9.3.6.6, 9.4.3.2, 9.5,3.6). 

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Figure 9.2 Calculated (a) number and (b) GPC distributions for three polymers each with =100. The number distributions of chains formed by conventional radical polymerization with termination by disproportionation or chain transfer...

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