The Catalytic Oxidative Polymerization of 3-Hexylthiophene by Oxidation of Fe2+ to Fe 3

In the case of the oxidative polymerization of 3-hexylthiophene (3HT) with FeCl 3 , FeCl 3 is always required at a concentration four times higher than that of 3HT to produce high-molecular-weight P3HT. In order to avoid the use of excess FeCl 3 , it was considered that an oxidizer could assist the catalytic oxidative polymerization by oxidizing Fe 2+ to Fe 3+ . To determine an effective oxidation agent (Fe 2+ to Fe 3+ ), various oxidizers (Cl 2 , BPO, H 2 O 2 , ZrCl 4 , and (NH 4 ) 2 Ce(NO 3 ) 6 ) were examined. The obtained results indicated that Ce4+ was the most effective oxidant among those tried for the polymerization of 3HT. The polymer yield was typically 29–35% without the addition of (NH 4 ) 2 Ce(NO 3 ) 6 , but the yield improved to 53% with it. To confirm whether Fe 2+ was oxidized to Fe 3+ by Ce 4+ , a combination of Fe 2+ and Ce 4+ was used to perform an oxidative polymerization of 3HT. As a result, poly(3-hexylthiophene) was successfully obtained with the combination of FeCl 2 and (NH 4 ) 2 Ce(NO 3 ) 6 as oxidative agents. This result indicates that Fe 3+ was formed by the oxidation of Fe 2+ with Ce 4+ , followed by catalytic oxidative polymerization. Graphical Abstract