Kinetic theories for radical recombination

2 THE RATE OF REACTION AND DECAY OF RADICALS IN SOLIDS 3.2.1 Kinetic theories for radical recombination 

The rate of decay of trapped radicals in polymers depends on the nature of the radical, the chemical structure and crystallinity of the polymer, the temperature, the linear energy transfer and eventually the dose rate. 

The mode of radical production is also very important since it determines whether radical decay is due to (a) homogeneous combination with radicals from elsewhere in the polymer, or (b) recombination between radicals in pairs. 

We shall now examine in detail both of these cases. 

Formal kinetic treatments of the homogeneous bimolecular combination of radicals and of the homogeneous scavenging of radicals by the matrix or any additive in the solid phase has been given by Waite [216] and by Lebedev [217]. These recombinations usually occur in crystalline and glassy substances at temperatures close to the melting point or close to the glass or other phase-transition temperature. The recombination can then be described by the same kinetic expression (usually a second-order equation) until total decay is observed. 

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