N-alkyl Dithieno3,2-b:2’,3’-d Pyrroles-based Copolymers

摘要

Conjugated polymers have received considerable attention owing to their promise of more cost-effective processing than their inorganic counterparts. Another advantage of these materials is that they can be molecularly engineered to have tunable electronic and optical properties. The key to molecular engineering is the ability to control π conjugation through synthesis. One useful strategy to tuning π conjugation is the introduction of fused aromatic rings into the conjugated polymer backbone. The incorporation of fused rings leads to a more rigid and planar polymer backbone, therefore enhancing the effective π-conjugation and lowering the polymer band gap. Rasmussen has pioneered the use of N-alkyl dithieno [3,2-b:2’,3’-d]pyrrole (DTP) as a very promising fused-ring analogue of thiophene. It has a completely flat crystal structure, indicating good π conjugation across the fused rings. Upon polymerization, poly (N-alkyl dithieno[3,2-b:2’,3’-d]pyrroles (PDTPs) exhibit excellent stability in their oxidized state, have low band gaps, and show efficient red florescence in solution. However, PDTPs have generally exhibited low solubility and low molecular weight, which greatly inhibits their processability and utilization in electronic devices. To improve the solubility of PDTPs, we incorporate substituted thiophene units into the polymer backbone and generate a series of novel low band-gap copolymers with excellent solubility, high molecular weights, and interesting electronic properties.