(521d) Highly Controlled Synthesis of Poly(3-hexylthiophene) Using Droplet-Flow Microreactors

Poly(3-hexylthiophene) (P3HT) is the mainstay semiconducting polymer for a broad range of organic electronic devices, and in particular thin-film organic photovoltaic (OPV) cells. Despite being over two decades since the first reported synthesis, there remains an unresolved problem with batch-to-batch consistency of P3HT in terms of electronic performance and solution rheology â?? both critical factors to the commercial success of printed OPV modules.

The primary cause of inconsistent performance is the inability to source materials with consistent molecular weight distributions and purities. To address this obstacle we have developed a droplet-flow reactor approach for the preparation of P3HT and other related conjugated polymers.^1â??3 In contrast to conventional flask methods which suffer from scaling issues above the few-gram level, our flow approach may be scaled up to production levels in excess of 1 kg/day without loss of control over the chemistry, and is sufficient to meet current industrial demand.

In this talk we will discuss the background concepts behind the droplet-flow approach, and we will demonstrate how these reactors may be used to prepare well-defined P3HT-based materials with predictable properties. We will show how our new variant of the polymerization catalyst for P3HT provides a means of preparing polymers with a wide range of molecular weights while maintaining a high degree of control over the chain length polydispersity. We will further show how these droplet-flow reactors may be used to accurately tune the optoelectronic properties of P3HT by the controlled addition of an optically-distinct co-monomer into the polymer chain. To conclude we will discuss the use of bio-derived solvents in the P3HT synthesis, which enables full conversion to the product polymer to be achieved in just one minute - a significant reduction on flask methods that typically require several hours to reach completion.

(1) Bannock, J. H.; Krishnadasan, S. H.; Nightingale, A. M.; Yau, C. P.; Khaw, K.; Burkitt, D.; Halls, J. J. M.; Heeney, M.; de Mello, J. C. Adv. Funct. Mater. 2013, 23, 2123â??2129.

(2) Bannock, J. H.; Al-Hashimi, M.; Krishnadasan, S. H.; Halls, J. J. M.; Heeney, M.; de Mello, J. C. Mater. Horiz. 2014, 1, 214â??218.

(3) Bannock, J. H.; Xu, W.; Baïssas, T.; Heeney, M.; de Mello, J. C. Eur. Polym. J. 2016.