Theoretical conditions for propagation

Chain growth can only occur under suitable thermodynamic conditions. For the chains to have required properties, some chemical conditions must also be fulfilled. The possibility of the technical control of propagation depends on the rates of the respective reactions, i. e. on the kinetics of the process. 

As any other process, propagation can spontaneously proceed only when accompanied a decrease in the Gibbs energy (free enthalpy) of the system AG = AH - TAS (l) 

There must therefore exist some conditions where the rate of propagation is just equal to the rate of depropagation, i. e. where AG = 0. The temperature at which the rates of reaction (2) are equal in both directions is of special importance for polymerizations. 

Equations (1) and (2) indicate that AH and AS must both be either positive or negative 

The equilibrum constant K of eqn. (2) is given by the ratio of the propagation and depropagation rate constants, fep kd 

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