Taming Charge Transport and Mechanical Properties of Conjugated Polymers with Linear Siloxane Side Chains
Fengsheng Zhao, Ye Yuan, Yafei Ding, Yunfei Wang, Xiaohong Wang, Guobing Zhang, Xiaodan Gu, Longzhen Qiu
Abstract
A series of conjugated polymers on the basis of diketopyrrolopyrrole and thienothiophene with different lengths of linear hybrid siloxane-terminal side chains were designed and synthesized. The number of silicon atoms in the side chains was 3, 5, and 7 (PTDPPTT-Si-3, PTDPPTT-Si-5, and PTDPPTT-Si-7, respectively, with two accompanying reference polymers, PTDPPTT-Ref-1 and PTDPPTT-Ref-2). Compared with PTDPPTT-Si-3, PTDPPTT-Si-5 and PTDPPTT-Si-7 had longer siloxane-terminal groups, which allowed them to maintain higher solution processability and excellent mobilities of 2.44 and 2.18 cm–2 V–1 s–1, respectively. In addition, the extended siloxane segment has high flexibility, which provides a good opportunity to improve the mechanical properties of rigid conjugated polymers. PTDPPTT-Si-7 exhibited excellent ductility and a low tensile modulus of 108 ± 21 MPa and retained 80% of its initial electrical properties under 100% stretching, indicating that long linear siloxane side chain-modified semiconductor polymers have great potential for wearable electronics. Our research provides an important guiding principle concerning the molecular engineering of semiconductor polymers with siloxane side chains.