Structure vs. property relationships in high mobility fused thiophene polymers

A family of conjugated polymers with fused structures consisting of three to five thiophene rings and with the same alkyl side chains has been synthesized as a means to understand structure - property relationships. All three polymers showed well extended conjugation through the polymer backbone. X-ray diffraction study of the polymer thin films suggests that the polymer with the even number of fused thiophene rings forms a tight crystalline structure due to its tilted side chain arrangement. On the other hand, the polymers with the odd number of fused thiophene rings packed more loosely. Characterization in a field-effect transistor configuration showed that the mobility of the polymer with the even number of rings is one order of magnitude higher than its oddnumbered counterparts. Through this structure - property study, we demonstrate that proper design of the molecules and properly arranged side chain positions on the polymer backbone can greatly enhance polymer electronic properties