Manipulating Conjugated Polymer Backbone Dynamics Through Controlled Thermal Cleavage of Alkyl Side Chains

Authors

Haoyu Zhao, University of Southern Mississippi
Jordan J. Shanahan, University of North Carolina at Chapel Hill
Stephanie Samson, University of North Carolina at Chapel Hill
Zhaofan Li, North Dakota State University
Guorong Ma, University of Southern MississippiFollow
Nathaniel Prine, University of Southern MississippiFollow
Luke Galuska, University of Southern MississippiFollow
Yunfei Wang, University of Southern MississippiFollow
Wenjie Xia, North Dakota State UniversityFollow
Wei You, University of North Carolina at Chapel Hill
Xiaodan Gu, University of Southern MississippiFollow

Document Type

Article

Publication Date

8-9-2022

School

Polymer Science and Engineering

Abstract

The morphological stability of an organic photovoltaic (OPV) device is greatly affected by the dynamics of donors and acceptors occurring near the device's operational temperature. These dynamics can be quantified by the glass transition temperature (T_g) of conjugated polymers (CPs). Because flexible side chains possess much faster dynamics, the cleavage of the alkyl side chains will reduce chain dynamics, leading to a higher T_g. In this work, the T_gs for CPs are systematically studied with controlled side chain cleavage. Isothermal annealing of polythiophenes featuring thermally cleavable side chains at 140 °C, is found to remove more than 95% of alkyl side chains in 24 h, and raise the backbone T_g from 23 to 75 °C. Coarse grain molecular dynamics simulations are used to understand the T_g dependence on side chain cleavage. X-ray scattering indicates that the relative degree of crystallization remains constantduring isothermal annealing process. The effective conjugation length is not influenced by thermal cleavage; however, the density of chromophore is doubled after the complete removal of alkyl side chains. The combined effect of enhancing T_g and conserving crystalline structures during the thermal cleavage process can provide a pathway to improving the stability of optoelectronic properties in future OPV devices.

Publication Title

Macromolecular Rapid Communications

Recommended Citation

Zhao, H., Shanahan, J. J., Samson, S., Li, Z., Ma, G., Prine, N., Galuska, L., Wang, Y., Xia, W., You, W., Gu, X. (2022). Manipulating Conjugated Polymer Backbone Dynamics Through Controlled Thermal Cleavage of Alkyl Side Chains. Macromolecular Rapid Communications.
Available at: https://aquila.usm.edu/fac_pubs/20441