Kinetics of ionic chain-growth polymerization

The kinetic picture of cationic chain polymerization varies considerably. Much depends upon the mode of termination in any oarticular system. A general scheme for initiation, propagation, and termination is presented below. ° By representing the coinitiator as A, the initiator as RH, and the monomer as M, we can write  

In the above expressions, [HM. .. (AR) 1 represents the total concentration of all the propagating ion pairs K is the equilibrium constant for formation of initiating cations. When a steady state exists, the rates of initiation and termination are equal to each other  

The rates of the two transfer reactions, to a monomer or to a transferring agent (S), as well as spontaneous terminations can be written as 

The validity of the steady-state assumption in many cationic polymerizations may be questioned, because many reactions occur at such high rates that a steady state is not achieved. Nevertheless, the above equations were shown to be generally followed.  

The kinetic picture of anionic chain polymerization also depends mostly upon the specific reaction. For those that are initiated by metal amides in liquid anunonia, the rate of initiation can be shown to be as follows  

In the above expressions, [HM -(AR) ] represents the total concentration of all the propagating 

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