Alkoxy-substituted thiophenes have been shown to yield polymers with a reduced bandgap. An X-ray investigation of two symmetrical pentoxy-substituted 2,2'-bithienyls is reported, and their structure and packing described. It is suggested that the extra rigidity and packing stability of the alkoxythiophene oligomers and polymers accounts for their lower solubility and higher melting points compared to their alkyl-substituted analogues.