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Updated: Jul 9, 2025
From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
H-bond network, interfacial tension and chain melting temperature govern phospholipid self-assembly in ionic liquids
Livia Salvati Manni1, Wye-Khay Fong2, Kathleen Wood3
1School of Chemistry and University of Sydney Nano Institute, The University of Sydney, Sydney, NSW 2006, Australia; School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW 2308, Australia; School of Chemistry, Monash University, Wellington Road, Clayton, VIC 3800, Australia.
Hypothesis:
The self-assembly structures and phase behaviour of phospholipids in protic ionic liquids (ILs) depend on intermolecular forces that can be controlled through changes in the size, polarity, and H-bond capacity of the solvent.
Experiments:
The structure and temperature stability of the self-assembled phases formed by four phospholipids in three ILs was determined by a combination of small- and wide-angle X-ray scattering (SAXS and WAXS) and small-angle neutron scattering (SANS). The phospholipids have identical phosphocholine head groups but different alkyl tail lengths and saturations (DOPC, POPC, DPPC and DSPC), while the ILs' amphiphilicity, H-bond network density and polarity are varied between propylammonium nitrate (PAN) to ethylammonium nitrate (EAN) to ethanolammonium nitrate (EtAN).
Findings:
The observed structures and phase behaviour of the lipids becomes more surfactant-like with decreasing average solvent polarity, H-bond network density and surface tension. In PAN, all the investigated phospholipids behave like surfactants in water. In EAN they exhibit anomalous phase sequences and unexpected transitions as a function of temperature, while EtAN supports structures that share characteristics with water and EAN. Structures formed are also sensitive to proximity to the lipid chain melting temperature.
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