Trapping diffusion theory

Polyvinylchloride was the host polymer in a study of the diffusion of dimethyl-phthalate, dibutylphthalate, and dioctylphthalate, performed by Maklakov, Smechko, and Maklakov 60) between room temperature and 110 °C. Azancheev and Maklakov 61) extended this work to include polystyrene as host, and to dependences of diffusion on concentration. They concluded that the macromolecules did constrain and trap the phthalate molecules at high polymer concentration, but without inhibiting the mobility of these diluents at lower polymer concentrations, e.g., in the gel. They used a version of the free volume theory to give a semi-quantitative explanation of the temperature and molecular size dependence of phthalate diffusion. 

A theoretical analysis of the experimental kinetics for Vk centres in KC1-Tl, as well as for self-trapped holes in a-Al203 and Na-salt of DNA, is presented in [55]. The fitting of theory to the experimental curves is shown in Fig. 4.4. Partial agreement of theory and experiment observed in the particular case of Vk centres was attributed to the violation of the continuous approximation in the diffusion description. This point is discussed in detail below in Section 4.3. Note in conclusion that the fact of the observation of prolonged increase in recombination intensity itself demonstrated slow mobility of defects. In the case of pure irradiated crystals, it is a strong... 

The latter theory of intramolecular electron transfer in nonconjugated polyelectrolytes, which may find support in the behaviour of the ribonuclease-copper(n) system (Levitzky and Anbar, 1967), is in accord with the observed agreement between the specific rates of gelatine, lysozyme and ribonuclease and the sum of specific rates of the constituent amino-acid residues (Braams, 1965, 1967). The latter agreement may, however, be fortuitous, and these proteins, which react at rates approaching the diffusion-controlled limit, may act as overall electron traps according to the first mechanism. 

The most general theory valid at the arbitrary diffusion coefficients, DA, DB, and D(, also corrects only the concentration dependence in the denominator of Eq. (3.712), but in full accordance with both the target and trap limits [255]. 

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