Polymer chains semiconduction

Recently it has been demonstrated by Guittard et al. that the electrochemical polymerization of semifluorinated thiophenes (226) [407], 3,4-ethylenediox-ythiophenes (227) [408], fluorenes [408], and 3,4-alkylenedioxypyrroles (230) [409] allowed the deposition of semiconducting polymer films with excellent antiwetting properties (superhydrophobic and lipophobic, see Fig. 73). Additional aromatics inserted between fluorinated tail and polymer chain (compounds 228, 231) improve mesogenity and in this way decrease the mobility of the Rp-chains, preorganize the molecules, and thus improve the antiwetting properties [388, 410]. 

Many other air-stable conducting polymers followed (Fig. 12.10) polypyrrole, polythiophene, polyaniline (which had been known since the nineteenth century as "aniline black"), and so on (Table 12.4). These polymers are semiconducting, not metallic, when "doped" with electron donors or acceptors the individual conjugated chains have finite length, so the conductivity is limited by chain-to-chain hopping. Also, if the individual strands exceed four or so oligomers, the conjugation tends to decrease, as the strand tends to adopt a screw-type distortion. The transport within each strand is attributed to polarons and bipolarons. 

Depending on their coordination in the backbone network, group IV elements can form extended, covalently bonded structures of different dimensionality. As the most commonly known example, the fourfold coordination of the sp hybridized atoms leads to the three-dimensional (3D) crystalline solids diamond, c-Si, c-Ge, and a-Sn with their well-known semiconducting properties. On the other hand, linear (ID) polymer chains (XR2) with X = C, Si, Ge, Sn are based on a twofold coordination of the backbone atoms and are of great importance in organic and inorganic polymer chemistry. ... 

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