An illustrative polymerization procedure for generating very high-molecular weight polymer 1 is as follows: To a Schlenk flask was added 3,6-bis(5-bromothiophen-2-yl)-2,5-bis(2-octyl-1-dodecyl)pyrrolo[3,4-c]pyrrole- 1,4-dione (0.2 mmol), 2,5-bis(trimethylstannyl)thieno[3,2-b]thiophene (0.2 mmol), tri(o-totyl)phosphine (8 mol% equivalent), tris(dibenzylideneacetone)-dipalladium (2 mol% equivalent) and dry chlorobenzene (20 ml) under a nitrogen atmosphere. The flask was securely sealed and stirred for 72 h at 130°C. After cooling to room temperature, the reaction mixture was poured into a stirring mixture of methanol (100 ml) and concentrated hydrochloric acid (8 ml) and stirred for 16 h. The precipitated product was collected by filtration and subjected to consecutive Soxhlet extractions with ethanol, ethyl acetate, chloroform and chlorobenzene. The final chlorobenzene extraction was vacuum evaporated and dried under vacuum to afford electrically pure polymer 1 in 56% yields.