Defect Analysis of High Electron Mobility Diketopyrrolopyrrole Copolymers Made by Direct Arylation Polycondensation

• Published in: Macromolecules Vol. 48; no. 20; pp. 7481 - 7488
• Main Authors: Broll, Sebastian, Nübling, Fritz, Luzio, Alessandro, Lentzas, Dimitros, Komber, Hartmut, Caironi, Mario, Sommer, Michael
• Format: Journal Article
• Language: English
• Published: American Chemical Society 27.10.2015
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.5b01843

Defect structures in high-performance conjugated polymers are generally known but still challenging to characterize on a quantitative basis. Here, we present a detailed analysis of backbone topology of a series of copolymers PDPPTh2F4 having alternating dithienyl­diketo­pyrrolopyrrole (DPPTh2) and tetrafluoro­benzene (F4) units made by direct arylation polycondensation (DAP). In contrast to early expectations of unselective C–H activation during the DAP of monomers with multiple C–H bonds, detailed structure analysis by high-temperature 1H NMR spectroscopy reveals well-defined and alternating backbones with a quantifiable amount of 0–12% DPPTh2 homocouplings as the only defect structure in the main chain. Homocoupled −DPPTh2–DPPTh2– structural units are additionally characterized by UV–vis spectroscopy. While −DPPTh2–H end groups are inert to other side reactions, −F4–Br end groups are weakly susceptible to both dehalogenation and reaction with toluene. However, despite the presence of DPPTh2 homocouplings, high field-effect transistor electron mobilities up to ∼0.6 cm2/(V s) are achieved. This study highlights both that DPPTh2 homocouplings pose a prevalent structural defect in DPPTh2-based conjugated polymers made by DAP and that a very simple four-step DAP protocol can yield materials with varying molar mass and excellent n-type transistor performance.