Influence of Side Chain Interdigitation On Strain and Charge Mobility of Planar Indacenodithiophene Copolymers

Authors

Parker J.S. Sommerville, University of Washington
Alex H. Balzer, Georgia Institute of Technology
Garrett Lecroy, Stanford University
Lorenzo Guio, University of Washington
Yunfei Wang, University of Southern MississippiFollow
Jonathan W. Onorato, University of Washington
Nadzeya A. Kukhta, University of Washington
Xiaodan Gu, University of Southern MississippiFollow
Alberto Salleo, Stanford University
Natalie Stingelin, Georgia Institute of Technology
Christine K. Luscombe, University of Washington

Document Type

Article

Publication Date

9-29-2022

School

Polymer Science and Engineering

Abstract

Indacenodithiophene (IDT) copolymers are a class of conjugated polymers that have limited long-range order and high hole mobilities, which makes them promising candidates for use in deformable electronic devices. Key to their high hole mobilities is the coplanar monomer repeat units within the backbone. Poly(indacenodithiophene-benzothiadiazole) (PIDT_C16-BT) and poly(indacenodithiophene-thiapyrollodione) (PIDT_C16-TPD_C1) are two IDT copolymers with planar backbones, but they are brittle at low molecular weight and have unsuitably high elastic moduli. Substitution of the hexadecane (C₁₆) side chains of the IDT monomer with isocane (C₂₀) side chains was performed to generate a new BT-containing IDT copolymer: PIDT_C20-BT. Substitution of the methyl (C₁) side chain on the TPD monomer for an octyl (C₈) and 6-ethylundecane (C_13B) afford two new TPD-containing IDT copolymers named PIDT_C16-TPD_C8 and PIDT_C16-TPD_C13B, respectively. Both PIDT_C16-TPD_C8 and PIDT_C16-TPD_C13B are relatively well deformable, have a low yield strain, and display significantly reduced elastic moduli. These mechanical properties manifest themselves because the lengthened side chains extending from the TPD-monomer inhibit precise intermolecular ordering. In PIDT_C16-BT, PIDT_C20-BT and PIDT_C16-TPD_C1 side chain ordering can occur because the side chains are only present on the IDT subunit, but this results in brittle thin films. In contrast, PIDT_C16-TPD_C8 and PIDT_C16-TPD_C13B have disordered side chains, which seems to lead to low hole mobilities. These results suggest that disrupting the interdigitation in IDT copolymers through comonomer side chain extension leads to more ductile thin films with lower elastic moduli, but decreased hole mobility because of altered local order in the respective thin films. Our work, thus, highlights the trade-off between molecular packing structure for deformable electronic materials and provides guidance for designing new conjugated polymers for stretchable electronics.

Publication Title

ACS Polymers Au

Recommended Citation

Sommerville, P. J., Balzer, A. H., Lecroy, G., Guio, L., Wang, Y., Onorato, J. W., Kukhta, N. A., Gu, X., Salleo, A., Stingelin, N., Luscombe, C. K. (2022). Influence of Side Chain Interdigitation On Strain and Charge Mobility of Planar Indacenodithiophene Copolymers. ACS Polymers Au.
Available at: https://aquila.usm.edu/fac_pubs/20588