Statistical copolymers of thiophene-3-carboxylates and selenophene-3-carboxylates; 77Se NMR as a tool to examine copolymer sequence in selenophene-based conjugated polymers

• Published in: Polymer chemistry 2022-09, Vol.13 (37), p.5316-5324
• Main Authors: Kawakami, Manami, Schulz, Karl H G, Varni, Anthony J, Tormena, Claudio F, Gil, Roberto R, Noonan, Kevin J T
• Format: Article
• Language: English
• Subjects: Carboxylates; Copolymerization; Copolymers; Cross coupling; Molecular weight distribution; NMR; Nuclear magnetic resonance; Palladium; Polymer chemistry; Polymers
• ISSN: 1759-9954; 1759-9962
• DOI: 10.1039/d2py00777k

Herein, we demonstrate that homopolymerization and statistical copolymerization of 2-ethylhexyl thiophene-3-carboxylate and 2-ethylhexyl selenophene-3-carboxylate monomers is possible via Suzuki–Miyaura cross-coupling. A commercially available palladium catalyst ([1,3-bis(2,6-di-3-pentylphenyl)imidazol-2-ylidene](3-chloropyridyl)dichloropalladium(ii) or PEPPSI-IPent) was employed to prepare regioregular conjugated polymers with high molecular weights (∼20–30 kg mol−1), and relatively narrow molecular weight distributions. The optical bandgap in the copolymer series could be reduced by increasing the concentration of selenophene-3-carboxylate in the material. Configurational triads were observed in the 1H NMR spectra of the statistical copolymers, which were assigned using a combination of 2D NMR techniques. The use of a 1H–77Se HSQC spectrum to further examine sequence distribution in the statistical copolymers revealed how 77Se NMR can be used as a tool to examine the microstructure of Se-containing conjugated polymers.