Disordered conformations chemical defects

However, in most experimental systems, the manifestations of the polaronic character of the charge carriers are masked by the effects of disorder. In any solution-deposited thin him, disorder is present and causes the energy of a polaronic charge carrier on a particular site to vary across the polymer network. Variations of the local conformation of the polymer backbone, presence of chemical impurities or structural defects of the polymer backbone, or dipolar disorder due to random orientation of polar groups of the polymer semiconductor or the gate dielectric result in a signihcant broadening of the electronic density of states. 

First of all, disorder in crystals arises from thermal motion of atoms around their equilibrium positions (thermal disorder). Disorder may also originate from the presence of defects in the lattice, due, for instance, to substitution of atoms (or group of atoms) with atoms (or group of atoms) of a different chemical nature, inclusion of structural motifs in interstitial lattice positions, or when structural units may pack in the same basic crystal lattice in different orientations or in a different conformation [63,64]. The presence of defects in the crystals, in turn, may induce local deformation of the lattice (due to small displacements of atoms from their average positions), which helps relaxation of local stresses, and causes diffuse scattering. 

If at least one site occupation in the list of atomic coordinates is less than one and this site is not filled by other atoms, there is atomic disorder or even a defect structure. This conforms the basis for several physical properties of the material, e.g., diffusion, ionic conductivity, chemical reactivity. Superconductivity is a special phenomenon. ... 

Figure 2.29 Limit-ordered models of packing of forms II [31] (a) and IV [67] (c) of sPP and model of a conformationally disordered modification, presenting kink-bands (b), intermediate between forms II and IV. A kink-band in the form II of sPP, with (T2G2)n helices, is characterized by a defective region with (T2G2T6G2)n conformational sequence, as in form IV [154, 155]. Reprinted from Reference [143] with permission from American Chemical Society, Copyright 2006.

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