Conformational Heterogeneity and Interchain Percolation Revealed in an Amorphous Conjugated Polymer

Abstract

Conjugated polymers are employed in a variety of application areas due to their bright fluorescence and strong biocompatibility. However, understanding the structure of amorphous conjugated polymers on the nanoscale is extremely challenging compared to their related crystalline phases. Using a bespoke classical force field, we study amorphous poly(9,9-di- n -octylfluorene- alt -benzothiadiazole) (F8BT) with molecular dynamics simulations to investigate the role that its nanoscale structure plays in controlling its emergent (and all-important) optical properties. Notably, we show that a giant percolating cluster exists within amorphous F8BT, which has ramifications in understanding the nature of interchain species that drive the quantum yield reduction and bathochromic shift observed in conjugated polymer-based devices and nanostructures. We also show that distinct conformations can be unravelled from within the disordered structure of amorphous F8BT using a two-stage machine learning protocol, highlighting a link between molecular conformation and ring stacking propensity. This work provides predictive understanding by which to enhance the optical properties of next-generation conjugated polymer-based devices and materials by rational, simulation-led design principles.

Modular Software for Generating and Modelling Diverse Polymer Databases

“…These dihedrals are generally poorly captured by the existing parameters within classical forcefields. 28,39 Thus having the capability to rapidly identify those dihedrals then allows the user to easily set up the necessary ab initio simulations required to determine the potential energy landscape of those dihedrals, which then can be used to reparameterize the forcefield for those dihedrals.…”

“…In more recent years, access to ever-growing computational power has allowed the materials modelling community to carry out increasingly complex investigations of polymeric materials. [21][22][23][24][25][26][27][28] Modern computer simulation studies provide predictive understanding of molecular interactions and mechanisms that determine the bulk-scale properties of polymers of interest. In tandem with experimental data, this combined insight yields rational design principles for new polymers with enhanced target properties.…”

“…PySoftK can also be used in the parameterization of dihedral terms in conjugated polymers, which are commonly poorly defined by standard classical forcefields. 28,39 Finally, we briefly review the steps that have been taken when developing the code to ensure it can be successfully used in a broad range of applications.…”

Modular Software for Generating and Modeling Diverse Polymer Databases

“…Polymeric materials have been the focus of a significant amount of scientific research for many decades. In more recent years, access to ever-growing computational power has allowed the materials modeling community to carry out increasingly complex investigations of polymeric materials. − Modern computer simulation studies provide predictive understanding of molecular interactions and mechanisms that determine the bulk-scale properties of polymers of interest. In tandem with experimental data, this combined insight yields rational design principles for new polymers with enhanced target properties.…”

“…We subsequently demonstrate the various functionalities that are found within the code to facilitate high-throughput molecular modeling calculations. PySoftK can also be used in the parametrization of dihedral terms in conjugated polymers, which are commonly poorly defined by standard classical force fields. , Finally, we briefly review the steps that have been taken when developing the code to ensure it can be successfully used in a broad range of applications.…”