A technique is described for the preparation of polymers according to a process in which the starting compound of formula (I) is polymerized in the presence of a base in an organic solvent. No end chain controlling agents are required during the polymerization to obtain soluble precursor polymers. The precursor polymer such obtained comprises structural units of the formula (II). In a next step, the precursor polymer (II) is subjected to a conversion reaction towards a soluble or insoluble conjugated polymer by thermal treatment. The arylene or heteroarylene polymer comprises structural units of the formula III. In this process the dithiocarbamate group acts as a leaving group and permits the formation of a precursor polymer of structural formula (II), which has an average molecular weight from 5000 to 1000000 Dalton and is soluble in common organic solvents. The precursor polymer with structural units of formula (II) is thermally converted to the conjugated polymer with structural formula (III) ##STR00001##