The present invention relates to a class of conducting oligomers and polymers and to a method for the preparation of the same. The conducting oligomers and polymers contain an end-capping group, which is non-electrically conductive and contains at least one branch point. The branched end-capping groups are made by a method that first substitutes the branched group on the heteroaromatic monomer, particularly at the "2" position on these monomers. In a second step, the end-capping intermediate is co-polymerized with one or more additional heteroaromatic monomers to form capped conducting oligomers and polymers.