Nanoconfined imidazolium ionic liquids
Doktorsavhandling, 2022

Long-chain ionic liquids are attracting interest as alternatives to their short-chain analogues as electrolytes. At the same time, they are also considered as alternatives to mesogens and conventional surfactants as templates. Interestingly, the nanoconfinement of long-chain ionic liquids in a solid and porous matrix (to result in a macroscopically solid hybrid material) can in some cases result in improved properties. This is due to the different chemical and steric environment to which the ionic liquid is exposed in confinement.

In this work, the effect of nanoconfinement on the mechanism of proton transport and the capacitive behaviour of the protic ionic liquid HC8imTFSI (1-octylimidazolium bis(trifluromethane-sulfonyl)imide) was studied. With this aim, proton conduction was investigated by broadband dielectric spectroscopy and pulsed-field gradient nuclear magnetic resonance spectroscopy, considering a mixture of imidazole and HC8imTFSI inside hydrophobised mesoporous silica. Results show that even inside narrow pores only ca 5 nm wide, the self-diffusion of the confined ionic liquid is unrestricted, due to weak interactions between the cations and the pore walls. By contrast, when pure HC8imTFSI was confined in the pores of hydrophilic silica, ca 3.5 nm wide, results from electrochemical impedance spectroscopy combined with equivalent circuit modelling indicated a high in-pore resistance. A further important finding is that at the in-pore protic ionic liquid/electrode interface an increased specific capacitance was measured, suggesting a higher charge density than for the interface between the electrode and the bulk protic ionic liquid.

Another aspect that has been considered in this thesis, is the ability of long-chain ionic liquids to function as a templating agent. The templating mechanism, the limitations associated to the chemical structure and the resulting pore morphology have been investigated. Results have revealed that tetradecyl- and hexadecyl-methylimidazolium chloride are suitable soft-templates for the formation of vertically aligned, uniform, channel-like pores, running through the entire thickness of a silica film deposited with the electrochemically assisted self-assembly method. By contrast, dodecyl-methylimidazolium chloride as well as the protic analogue hexadecyl-imidazolium chloride do not show a templating function under the investigated synthetic conditions. In all cases studied, the mechanism of pore formation is critically discussed.

surface active ionic liquids

protic ionic liquids


oriented and parallel nanochannels

Pater Noster (2034), Kemihuset, Kemigården 4, Göteborg
Opponent: Peter Hesemann, Dr.


Szilvia Vavra

Chalmers, Kemi och kemiteknik, Tillämpad kemi

Transport Properties and Local Structure of an Imidazole/Protic Ionic Liquid Mixture Confined in the Mesopores of Hydrophobic Silica

Journal of Physical Chemistry C,; Vol. 125(2021)p. 2607-2618

Artikel i vetenskaplig tidskrift

Charge transfer and electrical double layer of an amphiphilic protic ionic liquid in bulk and when confined in nanochannels

Physical Chemistry Chemical Physics,; Vol. 24(2022)p. 24469-24479

Artikel i vetenskaplig tidskrift

Salts, like table salt in the form of NaCl, are made of ions. Ionic liquids also contain ions only, but they are liquid below 100 °C. In addition, as ions are mobile in the liquid state, ionic liquids can transfer charge. Therefore, they are classified as ion conductors. Ionic liquids are useful for electrochemical devices, e.g. supercapacitors or fuel cells, in which the flow of the ions is simultaneous with the flow of electrons (electricity); this can be used for storing energy or to drive a device. Nevertheless, the wide commercial use of ionic liquids is hampered by some issues; for example, the ionic liquids that have been found to be good ion conductors tend to absorb water from air, which lowers their performance. This thesis focuses on ionic liquids that are not sensitive to water and are relatively cheap and easy to prepare; nonetheless their performance can still be improved. A current question of commercial and scientific interest is how these ionic liquids can transport charge in a confining space that compares to the size of the ionic liquid’s ions. Just to put this into context, the size of the space in which the ionic liquids are studied is on the nanometer scale; one nanometer being a billionth of a meter.


Nanovetenskap och nanoteknik







Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5078



Pater Noster (2034), Kemihuset, Kemigården 4, Göteborg


Opponent: Peter Hesemann, Dr.

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