Synthesis and Electronic Properties of Diketopyrrolopyrrole-Based Polymers with and without Ring-Fusion
Journal article, 2021

Diketopyrrolopyrroles (DPP) have been recognized as a promising acceptor unit for construction of semiconducting donor-acceptor (D-A) polymers, which are typically flanked by spacers such as thiophene rings via a carbon-carbon single bond formation. It may suffer from a decrease in the coplanarity of the molecules especially when bulky side chains are installed. In this work, the two N atoms in the DPP unit are further fused with C-3 of the two flanking thiophene rings, yielding a π-expanded, very planar fused-ring building block (DPPFu). A novel DPPFu-based D-A copolymer (PBDTT-DPPFu) was successfully synthesized, consisting of a benzo[1,2-b:4,5-b′]dithiophene (BDTT) unit as a donor and a DPPFu unit as an acceptor. For comparison, the unfused DPP-based counterpart PBDTT-DPP was also synthesized. Two dodecyl alkyl chains were attached to thiophene rings of DPP moieties to ensure good solubility of the DPPFu-based polymer. The influence of the ring-fusion effect on their structure, photophysical properties, electronic properties, molecular packing, and charge transport properties is investigated. Ring-fusion enhances the intermolecular interactions of PBDTT-DPPFu polymer chains as indicated by density functional theory calculation and analysis of electrostatic potential and van der Waals potential and results in significantly improved molecular packing for both the in-plane and out-of-plane directions as suggested by X-ray measurements. Finally, we correlate the molecular packing to the device performance by fabricating field-effect transistors based on these two polymers. The charge carrier mobility of the ring-fused polymer PBDTT-DPPFu is significantly higher as compared to the PBDTT-DPP polymer without ring-fusion, although PBDTT-DPPFu exhibited a much lower number-average molecular weight of 17 kDa as compared to PBDTT-DPP with a molecular weight of 108 kDa. The results from our comparative study provide a robust way to increase the interchain interaction by ring-fusion-promoted coplanarity.

Author

Wenliu Zhuang

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Polymer Technology

Guangdong Industry Polytechnic

Suhao Wang

Linköping University

Qiang Tao

Chalmers, Chemistry and Chemical Engineering

Hunan Institute of Engineering

Wei Ma

Xi'an Jiaotong University

Magnus Berggren

Linköping University

S. Fabiano

Linköping University

W. G. Zhu

Changzhou University

Ergang Wang

Zhengzhou University

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Ergang Wang Group

Macromolecules

00249297 (ISSN) 15205835 (eISSN)

Vol. 54 2 970-980

Subject Categories

Polymer Chemistry

DOI

10.1021/acs.macromol.0c02326

More information

Latest update

3/18/2021