Non-stationary states of radical polymerizations

It is a gross error to apply stationary state theory to non-stationary polymerizations, of which many exist. In a great majority of cases, the stationarity conditions are only fulfilled after a certain non-stationary phase in which the concentration of active centres increases. When this occurs in a kinetically pure medium, i.e. in the absence of inhibitors or other intervening compounds, it usually signifies slow initiation and is called the pre-effect. The general shape and meaning of the pre-effect is represented graphically in Fig. 5. For very small conversions ([M] [M]0) we can write [57] 

When monomer consumption in the initiation reaction is neglected (this is only permitted when long chains are generated), both sides of eqn. (43) are directly proportional to the concentration of growing radicals [M ]. 

A relatively high-molecular-weight, crystalline polyphenylacetylene of molecular mass of the order of 104 is formed by ionic or coordination polymerization (with WCI6 or (acac),Fe) [77]. In these polymerizations, termination is also a function of chain length [78]. 

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