Group theoretical aspects of conformational defects in polyethylene chains

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Abstract
The purely numerical computation of defect induced properties in polymers currently in use is time consuming since symmetry arguments cannot be exploited. Within the framework of Lifshitz's Green Function method, symmetry arguments well known from the treatment of chemical defects may be used for conformational defects, too, to reduce the computational work drastically. With this objective in mind, conformational defects are classified with respect to their local symmetry in a single polyethylene (PE) chain and, for irregular PE skeletons, the defect matrix is set up in terms of appropriate symmetry states. The defect matrix of a gauche position in an otherwise transplanar PE backbone is explicitly given and the projected densities of states of this system are calculated. The applicability of optical selection rules, obtained from local symmetry, to bulk PE is briefly discussed.