Capacitance of films containing polymerized ionic liquids

Electrode-polymer interfaces, which encompass adsorbed layers of polymers, dictate
many of the properties of thin films such as capacitance, electric field experienced by
polymers and charge transport. To develop an understanding of electric field-induced
transformations of electrode-polymer interfaces, we have studied electrified interfaces of
an imidazolium based polymerized ionic liquid (PolyIL) using combinations of broadband
dielectric spectroscopy (BDS), specular neutron reflectivity and simulations based
on the Rayleigh dissipation function formalism. We demonstrated that the Rayleigh
dissipation function formalism provides key insights into charge storage, which include
information about capacitance of interface, thicknesses of absorbed and diffuse layers.
Overall, the camel-shaped dependence of the capacitance on applied voltage was
obtained which originated from responses of absorbed layer to applied
voltages. Furthermore, the diffuse layer contribution to the capacitance should decrease with
applied voltage (V ) as V^-1/2, which is a direct consequence of local incompressiblity/crowded nature of
the PolyIL melts.