Abstract

The scalable commercialization of organic electronics wherein p-conjugated polymers serve as the semiconductors hinges on precise control of the material electronic, redox, optical, and mechanical properties, which are each highly influenced by local and long-range morphology. Here, we undertake atomistic molecular dynamics (MD) simulations at three temperatures (150 K, 300 K, and 400 K) to assess the morphological and mechanical response of bulk poly(3-hexylthiophene) (P3HT), a representative homopolymer of interest as an organic semiconductor (OS). As P3HT is a semicrystalline polymer, we characterize mechanical properties for both amorphous and crystalline P3HT models to derive insights into structure–property relationships, including Young’s modulus (E) and Poisson’s ratio (n). Mechanical behaviors that arise as a consequence of kinetically induced molecular reorientations/transitions are described, including the determination of entanglement properties over the course of polymer deformation. Specifically, we analyze stress–strain curves to (1) elucidate how, and the extent to which, the rather tangled amorphous domains retain their ductility over temperature ranges that span known phase transitions, and (2) uncover the strength and mechanism of inter-chain mechanical coupling across lamellar stackings as a function of temperature. Generally, this work provides a molecular-level understanding of the thermomechanical behavior of p-conjugated polymers at regions where order or disorder dominates local packing, and prompts a more comprehensive description of the mechanical properties of these systems while recognizing their often inherently semicrystalline nature.

Document Type

Article

Publication Date

2024

Notes/Citation Information

© The Royal Society of Chemistry 2024

Digital Object Identifier (DOI)

https://doi.org/10.1039/d4tc03618b

Funding Information

This work was supported in part by the Office of Naval Research (ONR) through award number N00014-22-1-2179 (for simulations and data analyses) and the National Science Foundation (NSF) under cooperative agreement number 1849213 (force field develop- ment). Supercomputing resources were provided by the Department of Defense (DoD) through the DoD High Performance Computing Modernization Program (HPCMP; Project No. ONRDC40433481) and by the University of Kentucky Information Technology Department and Center for Computational Sciences (CCS).

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