Structural defects in polymers

We discuss a general formalism for characterizing a variety of structural defects in polymers and describe a method for studying their properties. The method combines density functional calculations on perfect, periodic chains with model calculations on the defect-containing chains, where the parameters entering the model calculations are extracted from the results of the density functional calculations. As examples we discuss solitons and polarons in conducting polymers and solitons in hydrogen-bonded polymers. Further examples are briefly mentioned and, finally, we present some proposals for extensions and improvements. (orig.)