The Kumada catalyst transfer polymerization (KCTP) was applied on dialkyl-substituted thieno[3,4-b]pyrazine monomer systems-a low-bandgap system consisting of a thiophene ring with a fused pyrazine ring which displays promising properties for use in electronic applications. The poly(thieno[3,4-b]pyrazine)s were synthesized through a chain-growth mechanism with best results using an external o-tolyl initiator. A block copolymer with poly(3-hexylthiophene) was successfully formed without impurities. It is shown by UV-vis, fluorescence, DSC, and AFM measurements that the electronically fundamentally different blocks influence each other substantially in terms of the self-assembly and the optical properties, generating materials properties than the constituting homopolymers.