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Amphiphilicity in Liquid Crystals and Beyond


   Department of Chemistry

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  Prof D W Bruce  No more applications being accepted  Competition Funded PhD Project (UK Students Only)

About the Project

Background

Amphiphilic compounds self-organise so that the incompatible parts of the molecule are separated from one another (e.g. micelles); the exact same principle holds for liquid crystals (LCs). In particular, perfluorinated (PFC) and hydrocarbon (HC) chains tend to be incompatible, and the inclusion of both in the same molecule directs the LC phase organisation strongly (see e.g. J. Phys. Chem. B, 2017, 121, 8817).

More recently, we have prepared and published (Liq. Cryst. – in press) a disc-like liquid-crystalline gold(III) complex containing both HC and PFC chains, which has very strange behaviour. Normally as you heat a liquid crystal, then the different LC phases become gradually more disordered, but in this complex there is a very disordered phase sandwiched between two much more ordered phases – an effect that has been observed only once before in discotic LCs back in the 1980s. Thus, the phase is thermodynamically in the wrong place. It is evident that this results from the amphiphilicity of the complex, but the important question is 'Why?' – how do we understand this remarkable observation and, more importantly, how can we deploy this predictively? This matters because properties and applications of LCs depend totally on their organisation and so to be able to exert this level of control is crucial.

Objectives

There are structural variations of the gold(III) complexes from which the study will start. Chain length, nature and position are important factors, which will be explored systematically. In addition, the 'backbone' ligand in the gold complexes is a 2,6-diphenylpyridine ' CNC pincer' ligand and this can be modified to prepare 2,6-dipyridylbenzene analogues (NCN pincers) from which we can access the related platinum(II) chemistry.

The same amphiphilicity will also be investigated in (organic) triphenylenes where systematic synthesis allows control over the position, number and nature of HC and PFC chains used.

There is, in addition, another aspect to this work, namely that using longer PFC chains reduces the solubility of compounds making aspects of the synthetic chemistry challenging. However, we have workarounds and strategies that make it all much easier and these in turn are based on a different type of amphiphilicity related to how things interact in solution. If we can understand and control this aspect, it will have great potential. Space precludes details here, but happy to discuss further.

Experimental Approach and Training

The programme is heavily synthetic but based upon well-defined approaches. A challenge is the low solubility resulting from introduction of PFC chains, but as noted above we have observed a possible general strategy to resolve this question. We will probe this idea further through this chemistry. Chemical characterisation will use NMR spectroscopy, CHN analysis and mass spectrometry, while LC characterisation employs optical microscopy, DSC and small-angle X-ray scattering as well as optical experiments to determine the sign of the phase birefringence. The student will gain a broadly based training across a range of techniques and methodologies.

Novelty

The out-of-sequence LC phase is a fascinating and almost unique observation, and being able to understand it and therefore control phase behaviour in new compounds presents a unique opportunity. There is a specialist X-ray group in Sheffield who want to collaborate with us on these complexes and the structural detail that they can find in the LC phase will give amazing insight into how these LCs 'work'. The range of molecules that we can make and the diversity of techniques we can bring to bear makes this a fascinating opportunity to undertake a unique project and gain a wide range of skills.

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/.

For more information about the project, click on the supervisor's name above to email the supervisor. For more information about the application process or funding, please click on email institution

This PhD will formally start on 1 October 2022. Induction activities may start a few days earlier.

To apply for this project, submit an online PhD in Chemistry application:

https://www.york.ac.uk/study/postgraduate/courses/apply?course=DRPCHESCHE3

You should hold or expect to achieve the equivalent of at least a UK upper second class degree in Chemistry or a related subject.  


Funding Notes

Fully funded for 3 years by the Department of Chemistry and covers: (i) a tax-free annual stipend at the standard Research Council rate (£15,609 for 2021-22), (ii) tuition fees at the Home rate, (iii) funding for consumables. See guidance for further details: https://www.york.ac.uk/chemistry/postgraduate/research/dept-stud/
Studentships are available to any student who is eligible to pay tuition fees at the home rate: https://www.york.ac.uk/study/postgraduate-research/fees/status/
Not all projects will be funded; candidates will be appointed via a competitive process.

References

• You should hold or expect to receive at least an upper second class degree in chemistry or a chemical sciences related subject
• Applicants should submit a PhD application to the University of York by 28 February 2022
• Supervisors may contact candidates either by email, telephone or web-chat
• Supervisors can nominate up to 2 candidates to be interviewed for the project
• The interview panel will shortlist candidates for interview from all those nominated
• Shortlisted candidates will be invited to a panel interview on 30th or 31st March or 1stApril
• The awarding committee will award studentships following the panel interviews
• Candidates will be notified of the outcome of the panel’s decision by email

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