Addition polymerisation without chain termination

Expressions for the overall rate of polymerisation and molecular weight distribution of polymer can be obtained from the scheme shown above if each of the reaction steps is assumed to be second order. When B is anionic in nature, it sometimes happens that only the equivalent of steps (62) and (63) occur. Thus 

In principle, eqns. (67)—(71) can be solved and the concentrations of each of the species can be determined as functions of time. Although —rg can be obtained as a homogeneous function of C-, it takes the form 

The number-average degree of polymerisation of the polymer, P , is given 

PwlPn is usually called the dispersity. When fej = kp for the anionic polymerisation discussed above (in a batch reactor) 

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For addition polymerisation without chain termination or chain transfer, eqns. (73) and (77) may be used for a batch reactor when fe = fep. Here, the growing chains have similar histories and hence the final molecular weight distribution can be very narrow. Similar results would be expected from a plug-flow reactor. The mole fraction of A , 7 , is given by... 

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