ma5b02643_si_001.pdf (275.06 kB)
Ordering Transition in Salt-Doped Diblock Copolymers
journal contribution
posted on 2016-04-25, 20:50 authored by Jian Qin, Juan J. de PabloLithium salt-doped
block copolymers offer promise for applications
as solid electrolytes in lithium ion batteries. Control of the conductivity
and mechanical properties of these materials for membrane applications
relies critically on the ability to predict and manipulate their microphase
separation temperature. Past attempts to predict the so-called “order–disorder
transition temperature” of copolymer electrolytes have relied
on approximate treatments of electrostatic interactions. In this work,
we introduce a coarse-grained simulation model that treats Coulomb
interactions explicitly, and we use it to investigate the ordering
transition of charged block copolymers. The order–disorder
transition temperature is determined from the ordering free energy,
which we calculate with a high level of precision using a density-of-states
approach. Our calculations allow us to discern a delicate competition
between two physical effects: ion association, which raises the transition
temperature, and solvent dilution, which lowers the transition temperature.
In the intermediate salt concentration regime, our results predict
that the order–disorder transition temperature increases with
salt content, in agreement with available experimental data.