Physics

Glass transition

Engineering

Conductivity

Control engineering

Ionic conductivity

Computational chemistry

Physical chemistry

Ionic liquid

Psychology

Chemical physics

Composite material

Catalysis

Electrode

Organic chemistry

Chemistry

Polymer chemistry

Degree of polymerization

Materials science

Decoupling (probability)

Ionic bonding

Relaxation (psychology)

Counterion

Polymerization

Polymer

Molecular dynamics

Electrolyte

Social psychology

Thermodynamics

ACS Macro Letters

We performed long-time all-atom molecular dynamics simulations of cationic polymerized ionic liquids with eight mobile counterions, systematically varying size and shape to probe their influence on the decoupling of conductivity from polymer segmental dynamics. We demonstrated rigorous identification of the dilatometric glass-transition temperature (Tg) for polymerized ionic liquids using an all-atom force field. Polymer segmental relaxation rates are presumed to be consistent for different materials at the same glass-transition-normalized temperature (Tg/T), allowing us to extract a relative order of decoupling by examining conductivity at the same Tg/T. Size, or ionic volume, cannot fully explain decoupling trends, but within certain geometric and chemical-specific classes, small ions generally show a higher degree of decoupling. This size effect is not universal and appears to be overcome when structural results reveal substantial coordination delocalization. We also reveal a universal inverse correlation between ion-association structural relaxation time and absolute conductivity for these polymerized ionic liquids, supporting the ion-hopping interpretation of ion mobility in polymerized ionic liquids.

Influence of Counterion Structure on Conductivity of Polymerized Ionic Liquids