Molecular understanding of effect of size asymmetry on morphology and dynamics of charge-containing polymers provides insight into designing ion conducting membranes for energy material applications. In this study, we investigate the influence of charged species size asymmetry on the microstructure of randomly distributed charges on ionomers and the dynamics of counterions. Through performing Coarse-Grained Molecular Dynamics (CGMD) simulations of model random ionomer melts (charged monomers with size σ-) with counterions of different sizes (σ+), we find that charged species size ratio (λ=σ-/σ+) has an impact on size and shape of ionic aggregates formed by charged monomers and counterions and also counterion mobility. Random ionomers with bigger size asymmetry ratio λ have a greater tendency to form ionic aggregates with more stretched chain-like shape, given certain charge fraction values. Furthermore, scattering functions show stronger long-range correlations with λ increasing. In order to study the effect of size asymmetry on ionic conductivity, we apply an external electric field to the simulated system. Interpretation of these results offers guidance for optimally choosing the size of counterions in the design of ion conducting materials.

Effect of size asymmetry on morphology and dynamics of ionomers

2019 Spring National Meeting

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