Developing inverse vulcanised polymers as functional coatings

A PhD studentship is available in the research group of Dr Tom Hasell, and working with Professor Jo Fothergill, starting in October 2025. This position will be based in the Department of Chemistry and will also use facilities in the Materials Innovation Factory (MIF).

This project will focus on synthetic methods for discovering and designing new functional materials derived from elemental sulfur. Sulfur is an industrial by-product, removed as an impurity in oil-refining. This has led to vast unwanted stockpiles of sulfur and resulted in low bulk prices. Sulfur is therefore a promising alternative feedstock to carbon for polymeric materials. Sulfur normally exists as S₈ rings – a small molecule with poor physical properties. On heating, these sulfur rings can open and polymerise to form long chains. However, because of the reversibility of sulfur bonds, these polymers are not stable, and decompose back to S₈ over time, even at room temperature. Inverse vulcanisation has made possible the production of high sulfur content polymers, stabilised against depolymerisation by crosslinking.¹ These polymers have applications in LiS batteries, IR transparent optics, thermal and electrical insulation, self-healing polymers, construction, and in heavy metal capture. Antimicrobial applications are underdeveloped in comparison, but we recently developed a set of sulfur polymers that have potent antimicrobial and antibiofilm activity against both Gram-positive (S. aureus) and Gram-negative (P. aeruginosa and E. coli) bacteria.^{2, 3}

Aims of the PhD project: The polymers must be made in such a way that they are soluble in organic solvents, to allow them to be coated onto substrates,⁴ but then further reacted to render them then insoluble and immobile.⁵ We recently developed such a technique but there is need/scope for structural variation/optimisation. The PhD student will develop the synthesis by modifying the organic crosslinkers used, introducing structural additives, varying sulfur content and rank, glass transition, hydrophobicity, as well as developing the coating process. Coating sulfur polymers onto surfaces allows their antimicrobial properties to be tested and used for applications. Coating onto porous supports gives a way to maximise their surface areas for heavy metal capture applications.^6,7 Antimicrobial testing will be conducted in conjunction with the group of co-supervisor Prof. Fothergill (Clinical Infection, Microbiology & Immunology). In parallel, the physical and deposition properties of the polymers will be investigated and improved to enable applications such as catheter coatings, wound dressings, and durable coatings. We have already shown sulfur polymers to be effective against species that are major causes of catheter-associated infections: Catheter-related bloodstream infections have an incidence of 1.1-5.5 per 1000 catheter days and are associated with increased morbidity, length of hospital stays and death. Bacteria do not readily develop resistance to sulfur compounds.

Skills Training: The student will gain skills in synthetic chemistry and polymer processing, as well as material (TGA/DSC/GPC/SEM) and general characterisation techniques (spectroscopy and diffraction). They may perform flexural, tensile, impact and abrasion resistance measurements. There will be opportunities for them to be learn microbiological techniques as part of applications testing.  There is an optional choice to take on paid teaching duties during the position.

Candidate: The position would suit a candidate with a background in chemistry, materials science, or a related discipline. They should have experience in, or interest to learn about, polymer chemistry, materials characterisation, and antimicrobial materials.