ma7b00125_si_001.pdf (145.56 kB)
Multiscale Simulations of Lamellar PS–PEO Block Copolymers Doped with LiPF6 Ions
journal contribution
posted on 2017-06-01, 15:50 authored by Vaidyanathan Sethuraman, Santosh Mogurampelly, Venkat GanesanWe report the results of atomistic
simulations of the structural
equilibrium properties of PS–PEO block copolymer (BCP) melt
in the ordered lamellar phase doped with LiPF6 salt. A
hybrid simulation strategy, consisting of steps of coarse-graining
and inverse coarse-graining, was employed to equilibrate the melt
at an atomistic resolution in the ordered phase. We characterize the
structural distributions between different atoms/ions and compare
the features arising in BCPs against the corresponding behavior in
PEO homopolymers for different salt concentrations. In addition, the
local structural distributions are characterized in the lamellar phase
as a function of distance from the interface. The cation–anion
radial distribution functions (RDF) display stronger coordination
in the block copolymer melts at high salt concentrations, whereas
the trends are reversed for low salt concentrations. Radial distribution
functions isolated in the PEO and PS domains demonstrate that the
stronger coordination seen in BCPs arises from the influence of both
the higher fraction of ions segregated in the PS phase and the influence
of interactions in the PS domain. Such a behavior also manifests in
the cation–anion clusters, which show a larger fraction of
free ions in the BCP. While the average number of free anions (cations)
decreases with increasing salt concentration, higher order aggregates
of LiPF6 increase with increasing salt concentration. Further,
the cation–anion RDFs display spatial heterogeneity, with a
stronger cation–anion binding in the interfacial region compared
to bulk of the PEO domain.