Post-irradiation polymerization effect

The auto-acceleration observed under such conditions is reduced ( = 1.15) and could partially result from non-steady-conditions but also from a "matrix effect" operating on the surface of unswollen polymer particles. It should be noted in this respect that the post-polymerization which is induced by the growing chains occluded in the precipitated polymer exhibits an initial rate very much lower than the rate observed during irradiation (Curve 1 in Figure 91 which suggests that the contribution of the growth of occluded chains to the over-all rate is small. 

The total activation energy for radiation polymerization varies within the limits of 0-41.8 kJ/mol. A small value of this energy causes that the radiation polymerization reaction rate is temperature independent within a few tens of Kelvins. A characteristic feature of the radiation polymerization is the presence of the retrospective effect (post-effect). It consists on the fact that after the cessation of irradiation the polymerization continues over many hours. This phenomenon concerns primarily the polymerization in solid phase or in solution precipitation. The reason for this phenomenon is the reduced mobility of macroradicals in solid phase and difficulties ending the chains by recombination. 

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