How <scp>side‐chain</scp> hydrophilicity modulates morphology and charge transport in mixed conducting polymers
Aditi Khot, Brett M. Savoie
Abstract
Abstract Organic mixed ionic‐electronic conductors (OMIECs) are a developing class of organic electronic materials distinguished by their dual modes of conduction. The side‐chains of OMIEC polymers are responsible for forming a percolating electrolyte phase that mediates doping and ionic conduction. Despite this critical role, design rules for OMIEC side‐chains are still nascent and their effects on OMIEC morphology and charge transport have yet to be systematically studied. Here we perform the first dedicated coarse‐grained molecular dynamics study of OMIECs where the side‐chain identity and distribution are systematically varied using a random copolymer architecture. The simulations recapitulate the nonlinear progression of the morphology from an interfacially gated electrolyte when large fractions of hydrophobic side‐chains are incorporated, to an electrolyte swelled morphology after crossing a threshold of approximately 40% polar side‐chains. Kinetic Monte Carlo simulations were used to characterize the charge transport behaviors in these systems, revealing two interesting maxima in the mobility at 40% and 100% polar side‐chain fractions, respectively. With respect to maximizing the charge mobility and conductivity, these simulations suggest that a uniform hydrophilic side‐chain distribution is optimal and that there are few advantages to using mixed side‐chains in a random copolymer architecture. These results also suggest several alternative side‐chain engineering strategies for optimizing OMIEC performance.