The new catalysts are able to achieve polymerisation with high selectivity, high molecular weight and low polydispersity. The starting monomers are 1,6-diynes – chains of seven carbon atoms including a triple bond at each end. These can form chains of either five- or six-membered rings, but the new catalyst is designed in such a way as to ensure six-membered rings are formed exclusively. This is one of very few instances in which this has been achieved.
By using a catalyst with very bulky ligands, the researchers have prevented chains from meeting each other and terminating prematurely, meaning polymerisation keeps going until a terminating molecule is deliberately added. This is known as 'living polymerisation'.
Finally, the researchers have used this method to create diblock copolymers – chains consisting of one type of monomer followed by a different type. Returning to the bead analogy, imagine a string where the first half is threaded exclusively with one shape of bead, and the second half is threaded with a different shape of bead.
Corresponding author Dr Tae-Lim Choi says: "This method lets us obtain semi-conducting materials with well-defined structures and fewer defects. This would hopefully lead to better electronic materials with higher performance in organic-based devices such as solar cells and transistors."
This work is expected to contribute to the development of more and better semi-conducting polymers, which would ultimately lead to making electronics lighter, more flexible and easier to carry.
This article is free to read in our open access, flagship journal Chemical Science: Tae-Lim Choi et al., Chem. Sci., 2019, Advance Article. DOI: 10.1039/C9SC01326A. You can access our 2019 ChemSci Picks in this article collection. Read more like this