Ionic liquids (ILs) are materials of significant interest owing to their low volatility and wide applicability, for example as solvents for catalysis, in the synthesis of nanomaterials, as electrolytes and in cleaning up natural gas streams. In addition, through appropriate molecular modification it is also possible to realise liquid-crystalline derivatives – ionic liquid crystals (ILCs) – which have the potential to combine the enviable properties of ILs with the anisotropy of liquid crystals (LCs). The group in York has interests in various related areas, which are outlined below.
There is real interest in preparing single-component materials that contain both hydrocarbon and fluorocarbon fragments, as the two are normally immiscible and so their presence in the same compound can have a profound effect on the way in which the materials self-organise over short (ILs) or longer (ILCs) length scales. Our interest in this is related to collaborative work on so-called SILPs (supported ionic liquid phases) in which ILs containing homogeneous catalysts are deposited as films on the surface of high-surface-area supports (e.g. mesoporous silicas) in order to prepare heterogenised catalysts of industrial importance. The nature of the gas/IL interface, of great importance in SILPs, can be controlled by the hydrocarbon/fluorocarbon balance, which can be a function either of the nature of the individual IL used or, more profitably, by using mixtures. This latter approach allows tuning of the IL properties over a range of compositions and is a more efficient approach to dialling in desired properties and optimising catalyst performance. These projects are carried out in collaboration with groups at Heriot Watt University (study of surface composition) and at Erlangen in Germany (catalysis).
In addition, the interest in amphiphilic ILCs also allows for the study of LC phase structures driven by the frustration exhibited due to the reduced packing options for the mesophase as a result of the amphiphilic nature of the LC.
Projects can be tailored to a large degree to accommodate the interests of those undertaking them, but the principal aspects are: (i) preparation of the new ILs/ILCs and their chemical characterisation, (ii) characterisation of their physical properties (e.g. surface tension, viscosity, conductivity, LC response), (iii) structural characterisation using small-angle scattering and surface reflectivity with both X-rays and neutrons. There is also scope for the preparation of SILPs and subsequent catalytic evaluation.
(i) Mixtures represent a powerful approach to tuning the properties of ILs and our work to date in this area shows that properties tend not to vary linearly with composition. As such, there is a real desire to understand the relationship between composition and properties given the potential benefits, and to move the work to the point where properties can be predicted with confidence.
(ii) Being able to exert control over the 2D organisation of LC fluids is of fundamental interest in understanding how potentially antagonistic interaction can be tensioned and accommodated. Some of this understanding spills over into the non-LC mixtures giving a pleasing synergy between the two broad project themes.
Depending on the precise project, the work includes: synthetic chemistry in which area the student will gain significant expertise, complemented by gaining expertise in the normal methods of chemical characterisation (NMR spectroscopy, mass spectrometry, single-crystal X-ray analysis); liquid crystal characterisation using optical microscopy, calorimetry and small-angle X-ray scattering (SAXS); physical characterisation including surface tension, conductivity, viscosity; structural characterisation using SAXS (in-house), and surface reflectivity and small-angle scattering using neutrons (Harwell National Facility) and catalysis. As such, the training provided is extremely broad.
All Chemistry research students have access to our innovative Doctoral Training in Chemistry (iDTC): cohort-based training to support the development of scientific, transferable and employability skills: https://www.york.ac.uk/chemistry/postgraduate/cdts/
The Department of Chemistry holds an Athena SWAN Gold Award and is committed to supporting equality and diversity for all staff and students. The Department strives to provide a working environment which allows all staff and students to contribute fully, to flourish, and to excel: https://www.york.ac.uk/chemistry/ed/ .