Quantitative Evidence of Mobile Ion Hopping in Polymerized Ionic Liquids

We demonstrate the dynamical heterogeneity and cooperative motion of ion transport in polymerized ionic liquids using atomistic molecular dynamics simulations and establish quantitative evidence of mobile ion hopping for the first time. The hopping of anions is dominantly interchain in nature and is generally facilitated by five associating cations from two chains. Intrachain hopping was found to be much less significant being mediating with fewer chains. The mobile anions tend to form string-like structures and move cooperatively; and the string length of concerted motion of mobile anions increases with decreasing temperature. Our results reveal the important role of a distance criterion in defining hopping events to elucidate the ion transport mechanism which has a significant consequence on rationalizing experimental observations and the design of novel polyILs.

Financial support of the U.S. Army Research Office under Contract No. W911NF-15-1-0501 and W911NF-16-1-0402 is greatly acknowledged. Computing resource was provided through XSEDE allocation DMR130078 at Stampede2 of TACC.