Energetics electrically active polymers

Polymerization of the fluoro monomers is carried out at temperatures in the range 20-60 °C and at pressures up to 60 MPa. Even in the case of the simple self-addition of vinyl fluoride molecules, the precise reaction conditions have a significant effect on the detailed structure of the resulting polymer. Because the molecules are not symmetrical, they can link to each other in the chain in three possible ways. These are the normal, and energetically favourable, head-to-taiT configuration (producing electrically inactive material) or the so-called defect combinations of head-to-head and tail-to-taiT [8]. The effect of the tow fraction of these defects present in the poly(vinylidene fluoride) prepared by standard routes is small, and the polymer crystallizes from the melt in a non-polar form. In contrast to this, polymerization of a mixture of vinyl fluoride and trifluoroethylene monomers results in many head-to-head sequences, the effect of which causes the polymer to crystallize in a potentially active form, a structure only attainable in poly(vinylidene fluoride) by vigorous mechanical reorientation. 

In the opening chapter, Evguenia Emelianova and Heinz Baessler analyze the dissociation of optically generated excitons into pairs of free carriers in the case of pure, blended and doped polymers. The effects of Gaussian disorder, temperature, and electric field on the photocarrier yield are investigated. As the presented analytical examination shows, energetic disorder enhances exciton dissociation. Moreover, the temperature dependence of the yield is weakened and loses the activated shape it exhibits in the case of moderate fields and zero disorder. 

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