Predicting the Mechanical Properties of Organic Semiconductors Using Coarse-Grained Molecular Dynamics Simulations

Journal Article (Journal Article)

The ability to predict the mechanical properties of organic semiconductors is of critical importance for roll-to-roll production and thermomechanical reliability of organic electronic devices. Here, we describe the use of coarse-grained molecular dynamics simulations to predict the density, tensile modulus, Poisson ratio, and glass transition temperature for poly(3-hexylthiophene) (P3HT) and its blend with C . In particular, we show that the resolution of the coarse-grained model has a strong effect on the predicted properties. We find that a one-site model, in which each 3-hexylthiophene unit is represented by one coarse-grained bead, predicts significantly inaccurate values of density and tensile modulus. In contrast, a three-site model, with one coarse-grained bead for the thiophene ring and two for the hexyl chain, predicts values that are very close to experimental measurements (density = 0.955 g cm , tensile modulus = 1.23 GPa, Poisson ratio = 0.35, and glass transition temperature = 290 K). The model also correctly predicts the strain-induced alignment of chains as well as the vitrification of P3HT by C and the corresponding increase in the tensile modulus (tensile modulus = 1.92 GPa, glass transition temperature = 310 K). We also observe a decrease in the radius of gyration and the density of entanglements of the P3HT chains with the addition C which may contribute to the experimentally noted brittleness of the composite material. Although extension of the model to poly(3-alkylthiophenes) (P3ATs) containing side chains longer than hexyl groups - nonyl (N) and dodecyl (DD) groups - correctly predicts the trend of decreasing modulus with increasing length of the side chain measured experimentally, obtaining absolute agreement for P3NT and P3DDT could not be accomplished by a straightforward extension of the three-site coarse-grained model, indicating limited transferability of such models. Nevertheless, the accurate values obtained for P3HT and P3HT:C blends suggest that coarse graining is a valuable approach for predicting the thermomechanical properties of organic semiconductors of similar or more complex architectures. 60 60 60 60 -3

Full Text

Duke Authors

Cited Authors

  • Root, SE; Savagatrup, S; Pais, CJ; Arya, G; Lipomi, DJ

Published Date

  • April 26, 2016

Published In

Volume / Issue

  • 49 / 7

Start / End Page

  • 2886 - 2894

Electronic International Standard Serial Number (EISSN)

  • 1520-5835

International Standard Serial Number (ISSN)

  • 0024-9297

Digital Object Identifier (DOI)

  • 10.1021/acs.macromol.6b00204

Citation Source

  • Scopus