Regioregularity and properties of the poly(3-hexylthiophene) synthesized by palladium catalyzed direct CH arylation polycondensation under different reaction conditions

• Pd-catalyzed direct CH polymerization of 2-bromo-3-hexylthiophene was investigated.
• Solvent shows great influence on the terminal groups and molecular weight of P3HT.
• β-Coupling was proposed to be the reason for the low regioregularity of P3HT.
• Application of the synthesized P3HT in polymer solar cell was investigated.

The effect of reaction conditions on Pd-catalyzed direct CH arylation polycondensation of 2-bromo-3-hexylthiophene to regioregular poly(3-hexylthiophene) (rr-P3HT) is exhibited. A wide range of reaction parameters, including palladium catalyst, ligand, reaction temperature and solvent, have been evaluated with a view to optimizing the polymerization conditions. For the first time, the end-groups of the synthesized polymer chains, confirmed by MALDI-TOF-MS measurement, were found to be significantly depended on the solvent used in reaction. Furthermore, homo-coupling and α or β coupling side-reactions were detected in a model oligomer synthesis reaction, which was supposed to be the reason for the low regioregularity of the resulting P3HT. Optical and electrochemical properties, as well as photovoltaic performance of the synthesized P3HT were investigated.

A series of influence parameters on Pd-catalyzed CH arylation polycondensation of 2-bromo-3-hexylthiophene are investigated. Solvent shows an important role on the terminal group. The β-coupling side reaction was confirmed by a model oligomer reaction, which was proposed as the reason for the low regioregularity of the polymers.Figure optionsDownload as PowerPoint slide