CDT Summer School 2019

This year’s CDT Summer School was a huge hit with external speakers, internal speakers, 1st year student talks and 2nd year student posters!

Congratulations to the 1st year presentation prize winners:

Michael Harris - 1st Prize Winner

Michael Harris - 1st Prize Winner

Freya Cleasby - Runner Up

Freya Cleasby - Runner Up

Kate Tatini - Runner-up

Kate Tatini - Runner-up

Our CDT students have been busy!!!!

Publications:

Thomas Robshaw, Sudhir Tukra, Deborah B. Hammond, Graham J. Leggett, Mark D. Ogden, Highly efficient fluoride extraction from simulant leachate of spent potlining via La-loaded chelating resin. An equilibrium study, Journal of Hazardous Materials, 2019, 361, 200-209 (https://doi.org/10.1016/j.jhazmat.2018.07.036)

Robshaw, T., Dawson, R. , Bonser, K. et al.,  Towards the implementation of an ion-exchange system for recovery of fluoride commodity chemicals. Kinetic and dynamic studies, Chemical Engineering Journal, 2019, 367, 149-159 (https://doi.org/10.1016/j.cej.2019.02.135)

K.V. Horoshenkov, J.-P. Groby, A. Hurrell, A 3-parameter analytical model for the acoustical properties of porous media, JASA, 2019, in publication

A. Romanova, K.V. Horoshenkov, A. Hurrell, An application of a parametric transducer to measure acoustic absorption of a living green wall, Applied Acoustics, 2019, 145, 89-97 (https://doi.org/10.1016/j.apacoust.2018.09.020)

T. Yang, R. Mishra, K.V. Horoshenkov, A. Hurrell, F. Saati, X. Xiong, A study of some airflow resistivity models for multi-component polyester fiber assembly, Applied Acoustics, 2018, 139, 75-81

K. Horoshenkov, A. Hurrell, M. Jiao, Are nano-fibers an emerging noise control solution?, JASA, 2018, 144(3), 1755-1755

A.I. Hurrell, K.V. Horoshenkov, M.T. Pelegrinis, The accuracy of some models for the airflow resistivity of nonwoven materials, Applied Acoustics, 2018, 130, 230-237 (https://doi.org/10.1016/j.apacoust.2017.09.024)

C.J. Fackler, A. Hurrell, D. Beaton, N. Xiang, Statistical analysis of multilayer porous absorbers with Bayesian inference, JASA, 2016, 139(4), 2070 

Matthew J. Rymaruk, Saul J. Hunter, Cate T. O’Brien, Steven L. Brown, Clive N. Williams, and Steven P. Armes, RAFT Dispersion Polymerization in Silicone Oil, Macromolecules. 2019, 52(7), 2822-2832 (https://doi.org/10.1021/acs.macromol.9b00129)

R. R. Gibson , S. P. Armes ,O. M. Musa and A. Fernyhough, End-group ionisation enables the use of poly(N-(2-methacryloyloxy)ethyl pyrrolidone) as an electrosteric stabiliser block for polymerisation-induced self-assembly in aqueous media,  Polymer Chemistry. 2019, 10, 1312-1323 (https://doi.org/10.1039/C8PY01619D)


Conference proceedings:

 A. Hurrell, M. Pelegrinis, Non-wovens Next Top Model?, Proceedings of the Institute of Acoustics, 2016, 38(1), 407 

Conference abstracts:

T.J. Robshaw, K. Bonser, G. Coxhill, R. Dawson, M.D. Ogden, Towards a combined leaching and ion-exchange system for valorisation of spent potlining waste, 7th International Conference on Sustainable Solid Waste Management, 2019, 26-29 June, Heraklion, Crete, Greece.

T.J. Robshaw, A.M. James, D.B. Hammond, R. Dawson, M.D. Ogden, Hydrophilic hypercrosslinked polymers for remarkably efficient fluoride capture. 7th International Conference on Sustainable Solid Waste Management, 2019, 26-29 June, Heraklion, Crete, Greece.

Thomas W. Franklin, Anthony J. Ryan, Oleksandr Mykhaylyk, Flow-induced crystallisation of polymers. , 257th ACS National Meeting and Exposition, 2019, 31 March - 4 April, Orlando, Florida.

Posters:

SAnPM 2019 AHurrell.gif
UKAN 1st Anniversary AHurrell.gif

Manchester Outreach Event

I took part in a Manchester outreach event on Sunday 10th March 2019 as part of British Science week. The aim of this event was to showcase science to the general public in my hometown which consist of mostly a minority ethnic asian background (Bangladeshis).

The event was a huge success and I could not have done it without CDT funding and the help of Joe Gaunt and Rob Dawson from the Chemistry Department at the University of Sheffield.

Please see attached, a few pictures and videos of the event, and media links below which were featured.

https://www.rochdaleonline.co.uk/news-features/2/news-headlines/126570/rochdale-science-extravaganza-returns-with-a-bang

https://www.rochdaleonline.co.uk/news-features/2/news-headlines/126680/weekly-column-mayor-mohammed-zaman

https://youtu.be/kHg1gdMNaLs

Article by Hasina Begum ; a 2nd year EPSRC Polymers, Soft Matter and Colloids CDT PhD student.

TR2 Papers Press Release

Polymer Centre members Dr Mark Ogden (senior lecturer, Dept. Chemical and Biological Engineering), Dr Robert Dawson (lecturer, Dept. Chemistry) and Tom Robshaw (CDT PhD Researcher) have published two research articles in the last six months. The papers are on the theme of treatment of spent potlining waste from the aluminium industry. This is a highly dangerous solid waste-form, on which there is no global consensus on correct disposal practice. It has been described as the most significant challenge for the future survival of the industry.

This however is only one side of the story. Spent potlining is a very rich source of labile fluoride. This is rapidly becoming a scarce resource, its parent mineral fluorspar (CaF 2 ) having made its way on to the EU “critical materials” list in 2014. There are estimated to be no more than 35 years-worth of geological fluorspar remaining in the world. This threatens future supply of fluorochemicals, which are needed for essentials such as non-stick coatings, transformers and circuit-breakers.

The researchers have conceptualised a complete treatment system for the potlining, involving crushing, chemical leaching, leachate treatment by ion-exchange for selective fluoride capture, fluoride elution, and finally precipitation and isolation of fluoride-bearing commodity chemicals. The two articles show development of the ion-exchange stage, for which a novel, lanthanum-loaded resin was chosen for the attempted extraction. The first paper (Journal of Hazardous Materials, 361, 200-209; DOI: 10.1016/j.jhazmat.2018.07.036) focusses on fundamental thermodynamic behaviour of the fluoride uptake, by way of loading isotherms, while the second (Chemical Engineering Journal, 367, 149-159; DOI: 10.1016/j.cej.2019.02.135) investigates the kinetics of the system and progresses to simulations of industrial conditions.

tom robshaw TR2.png

A number of key discoveries have added to the novelty of this work, principally that uptake of fluoride did not occur by the simple ligand-exchange process on the lanthanum centres, but by complexation of aqueous aluminium hydroxyfluorides. The chelating interaction allowed a lower energy uptake pathway, which was confirmed by an Arrhenius activation energy calculation. The use of X-ray photoelectron spectroscopy measurements, provided by Polymer Centre member Prof Graham Leggett, was instrumental in working out the unusual chemistry of the uptake process.

From a simulated ion-exchange column study, it was successfully argued that synthetic cryolite (Na 3 AlF 6 ) was a feasible recovery product and could be produced easily and at high purity. The system, if implemented industrially, would not only reduce the drain on global fluorspar reserves but also valorise the potlining and quickly offset any construction or conversion costs. A full technico-economic analysis on the proposed process is currently underway.

Article by Tom Robshaw; a 3rd year EPSRC Polymers, Soft Matter and Colloids CDT PhD student.

Journal club report - Extraction of uranium from non-saline and hypersaline conditions

Commercial ion exchange resins are formed from cross-linked polymers, which commonly have styrene/divinylbenzene or acrylate backbones. They can be either macro- or microporous and are produced on a large scale by a patented technology known as “spray-jetting”, which allows the formation of small beads, ~300 microns in diameter and of a narrow size distribution. Specific organic functional groups are then grafted to the polymer in multi-step synthetic processes. These can be designed to be selective to certain ions in aqueous solution, leading to purification and separation applications.

This research article is a collaborative effort between researchers at the University of Manchester and Dr Mark Ogden of the department of chemical and biological engineering and features the use of “Purolite S930+”, a resin bearing iminodiacetic acid functional groups. This resin is commercially available for decontamination of heavy metals from industrial wastewater. However here, a completely unique application is envisaged; that of selective uranyl uptake for geological uranium capture and recovery. This is an essential process for nuclear fuel production and consumes massive amounts of borehole water. This of course is a scarce resource in many countries and one line of thinking is to get round this problem by substituting seawater. However, this requires the ion-exchange resin to work well in challenging “hypersaline” conditions.

This study investigated the ability of S930+ to extract uranyl ions from a simulated aqueous feed solution, containing high levels of salt, iron, copper and sulfate. Encouragingly, the resin was found to have greater affinity for uranyl than the other two cations in the system and furthermore and crucially, there was negligible suppression of the uranyl uptake even at extremely high chloride concentrations (up to 6 M). Although careful control of the feed pH would be necessary, it is thought that there is real applied potential in an ion-exchange system of this nature in the uranium mining industry.

From a more fundamental perspective, the researchers were also able to perform Extended X-Ray Absorption Fine Structure (EXAFS) work at the Diamond Light Source in Oxfordshire. EXAFS is a type of spectroscopy that irradiates a sample with X-rays and measures the electron binding energies on the different atoms making up the sample. Through this, an accurate prediction could be made of how the uranyl cations were interacting with the resin functionality and it was revealed that a tridentate coordination mode was occurring (as seen in the accompanying diagram), with the other coordination sites being filed by a sulfate anion. This is the first time such behaviour has been properly qualified.

Original research article: “Extraction of uranium from non-saline and hypersaline conditions using iminodiacetic acid chelating resin Purolite S930+”, J.T.M. Amphlett, C.A. Sharrad and M.D.Ogden, Chemical Engineering Journal, 342, 133-141.

Article by Tom Robshaw; a 2nd year EPSRC Polymers, Soft Matter and Colloids CDT PhD student.

Starting PhD life

I recently (much less recently than it feels) started my PhD program at Sheffield under the CDT program for Polymers, Soft Matter and Colloids. I never anticipated, when I started my undergraduate degree here at Sheffield four years ago, that I’d end up staying and studying for a full 8 years. But when I got to my fourth year, I finally got a taste for what real research would be like. And I realised that I actually quite liked it. It was a world away from undergraduate labs, doing the same experiments over and over and knowing exactly what the outcome would be. Jumping through the same hoops as everyone else had done over the years. This way, I was getting results that no-one had ever seen before. Doing experiments that I thought of myself, in order to get the answers to questions that I’d generated.

Doing a PhD that was sponsored by industry was one thing that I was dubious about. I had previously done a year in industry and realised that it wasn’t for me. I loathed the rigidity and routine of each day. If there was a project I was truly interested in, I didn’t have any authority in how it was carried out. You just had to follow where the money was going. So doing a PhD for a company like Lubrizol, I was worried they were going to dictate everything I did. But the first 6 months they have entirely let me take the reins. They gave me a very broad and open question that I needed to answer. What makes a good pigment dispersant, good? This was something that I’d been thinking about for the past couple of years, since it was the basis of my third and fourth year project (albeit much more specific areas). Our first meeting consisted of a brainstorming session, where everyone pitched in various ideas and topics for me to explore during my PhD.

So since then, I’ve been trying to explore some of those ideas. Some things work, some things don’t. Some days you feel like everything is going great, some days you feel like you’re never going to find the answers. But despite this, I don’t think there is anywhere I would rather be. If I’ve stuck around this long, it can’t be that bad, right?

 

Article by Shannon North; a PhD Student on the EPSRC Polymers, Soft Matter and Colloids CDT programme. For more information, please contact Dr Joe Gaunt at the Polymer Centre.

Journal club report - Device for testing tennis shoe-court interactions

One of the challenges faced by tennis players is the interaction of their shoes with the court.  Tennis is played on a range of surfaces with different properties. For example, it it much easier to slide across a clay court than a hard court due to the lower friction with the less rough surface.  Researchers at the University of Sheffield investigated tennis shoe-court interactions and subsequently developed a portable mechanical device that can assess the quality of a tennis court which will be utilised by the International Tennis federation.

The rubber used to make tennis shoes is viscoelastic which means if a force is briefly applied to the material it is deformed and then returns to its original shape but when a force is applied for longer the material is deformed permanently.  The rubber soles are compressed against the surface of a tennis court and the rubber molds its shape to the roughness of the surface which is the cause of the friction. Therefore, when designing the test it was important to understand how load, surface roughness, shoe orientation, temperature and contact area contribute to the frictional force and a lab-based test rig was built for initial tests.  The researchers concluded that friction is mainly affected by sole surface temperature and surface roughness, and also the presence of a tread in the shoe sole.

In the design of the portable test device, the main features considered were reliability, size and weight for transportation and the ability to represent match play conditions well. Also, the test shoe needed to be interchangeable to allow testing of different sole materials and sizes. The final design consists of a test shoe slider attached to a sled with weights mounted on it, a pneumatic ram which provides a horizontal force to drive the sled. The horizontal force is applied until the test shoe slider is initiated and friction is measured.

The researchers hope that with further development the device could become part of a standard test to assess the quality of courts for elite tennis competitions and eventually be used to improve the quality of tennis courts for all players.

Article by Naomi Brown; a PhD Student on the EPSRC Polymers, Soft Matter and Colloids CDT programme. For more information, please contact Dr Joe Gaunt at the Polymer Centre.

Original Paper:

D. Ura, M Carré, Development of a Novel Portable Test Device to Measure the Tribological Behaviour of Shoe Interactions with Tennis Courts, Procedia Engineering, 147, 550-555, 2016.

Anti-microbial Graft Co-polymer Gels

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In 2008, researchers at the University of Sheffield published work regarding the synthesis of a triblock copolymer which formed a biocompatible gel suitable for use in wound dressings.1Unexpectedly, these gels also exhibited antimicrobial activity towards a range of microorganisms.2 This work has recently been further studied in a collaboration between the Department of Chemistry, the School of Clinical Dentistry and the Department of Engineering Materials at the University of Sheffield. This study aimed to understand more about the relationship between the polymer structure or architecture and its antimicrobial activity. This exciting research has potential be used in the future to provide alternatives to standard antibiotic treatments in a society where they have become much overused and antibacterial resistance is a growing problem.3

The original material synthesised had an ABA structure comprising of blocks of 2-hydroxypropyl methacrylate (HPMA) and 2-(methacryloyloxy) ethyl phosphorylcholine (MPC).An analogous graft-copolymer has been synthesised where PHPMA chains have been attached onto a PMPC chain via RAFT polymerisation, a form of controlled free-radical polymerisation used frequently by the research group of Professor Steve Armes in the Department of Chemistry. As well as this, AB diblock copolymers of the same monomers have been synthesised and shown to form self-assembled ‘worm-gels’. This novel material is biocompatible and has also been used in this study to determine if it is due to the gel property of polymers with this composition which leads to their antimicrobial properties.

Biological assays with staphylococcus aureus have been carried out on all of these PHPMA-PMPC materials to determine more about the mechanism of antimicrobial activity. Results have shown that the ‘worm-gels’, although biocompatible gels, were not antimicrobial. However, the graft copolymer gels have been shown inhibit bacterial growth and further studies by transmission electron microscopy show that this is likely due to the hydrophobic PHPMA chains in the gel penetrating and therefore causing damage to the bacterial membrane. Another interesting property of this graft copolymer gel is its thermoreversible gelation behaviour, making it applicable in the formation of antibacterial smart wound dressings.

Original article: Antimicrobial Graft Copolymer Gels. A. C. Harvey, J. Madsen, C. W. I. Douglas, S. MacNeil, S. P. Armes, Biomacromolecules, 2016, 2710-2718

Article by Rheanna Perry; a PhD Student on the EPSRC Polymers, Soft Matter and Colloids CDT programme. For more information, please contact Dr Joe Gaunt at the Polymer Centre.

(1)        Madsen, J.; Armes, S. P.; Bertal, K.; Lomas, H.; MacNeil, S.; Lewis, A. L. Biomacromolecules 2008, 9 (8), 2265–2275.

(2)         Bertal, K.; Shepherd, J.; Douglas, C. W. I.; Madsen, J.; Morse, A.; Edmondson, S.; Armes, S. P.; Lewis, A.; MacNeil, S. J. Mater. Sci. 2009, 44 (23), 6233–6246.

(3)           Harvey, A. C.; Madsen, J.; Douglas, C. W. I.; MacNeil, S.; Armes, S. P. Biomacromolecules 2016, 17 (8), 2710–2718.

Polymer Centre Highlight – Self-Assembled Graphene Oxide–Gelatin Nanocomposite Hydrogels

Hydrogels consist of a network of hydrophilic polymer chains held together by cross-links. These cross-links prevent the individual motion of polymer chains leading to the formation of a ‘gel’. Hydrogels closely resemble biological tissues due to their high water content and environmental sensitivities. This makes them attractive for biomedical applications, including tissue engineering and drug delivery.

The cross-links between polymer chains can be either physical or chemical. Physically cross-linked gels tend to be weak and the physical cross-links between the polymer chains are reversible. The weak mechanical properties limit the use of physically cross-linked gels in wider applications.

Chemically cross-linked gels are formed following a chemical reaction, where a chemical cross-linking agent is added to a solution of polymer chains.  By varying the quantity of cross-linking agent, the degree of cross-linking can be altered to optimise the gel properties for different applications. Although chemically cross-linked gels have attractive properties, the toxicity of cross-linking agents limits their use in biomedical applications.

Polymer centre academic Dr. Biqiong Chen has attempted to overcome these boundaries by synthesising novel, physically cross-linked, graphene oxide (GO)-gelatin nanocomposite hydrogels by self-assembly.

Both gelatin hydrogels and graphene-based materials have previously been studied for applications in drug delivery and tissue engineering. Gelatin is a denatured biopolymer, derived from collagen (found in skin and muscle). It has advantageous properties such as being biocompatible, biodegradable and low cost. GO, the oxidised form of graphene, has low toxicity. Gelatin-functionalised GO nanosheets are non-toxic and can be removed from the body by metabolism. Although these gels are physically cross-linked, multiple hydrogen-bonding and electrostatic interactions between the gelatin chains and GO sheets increase the strength of the 3D network significantly. These gels also exhibit self-healing properties.

The GO-gelatin hydrogels are also pH responsive and can be used for pH-sensitive drug release. At acidic pH (pH 1.7) the GO sheets form tightly packed aggregates preventing drug release. At neutral pH (pH 7.4) the pore size increases, promoting the diffusion of an encapsulated drug from the hydrogel to its surrounding liquid environment. This pH-sensitive behaviour would allow selective drug release into the intestine (pH 6.6-7.5) with minimal release in the stomach (pH 1.0-2.5). Conventional drug delivery methods can carry drugs to a specific location but are unable to protect the drug against the acidic and enzymatic environment of the stomach which can lead to the drug being released early or being altered. In contrast, these GO-gelatin hydrogels can protect the drug from enzymatic attack in the stomach. This allows the drug to be maintained and then released in a more controlled manner.

This research was published by Dr Biqiong Chen’s research group in the Journal of Polymer Science Part B and was supported by the University of Sheffield. Original Article: Y. Piao, B. Chen,  J. Polym. Sci. Part B: Polym. Phys, 2014, 53, 356 -367.

Article by Amy Cockram; a PhD Student on the EPSRC Polymers, Soft Matter and Colloids CDT programme. For more information, please contact Dr Joe Gaunt at the Polymer Centre.

An application of the Shear-Induced Polarized Light Imaging (SIPLI) Technique

Rheology is the study of flow and/or deformation of materials under applied forces. Using a plate-plate geometry, where the top and bottom features are flat plates, the measurement of rheological properties such as shear viscosity, normal stress, dynamic modulus and phase angle are enabled. Although this rotational rheology technique is well established, there is continuously growing interest in the combination of rotational rheology with other characterisation techniques to allow simultaneous measurements of viscoelasticity and additional physical properties.

Oleksandr Mykhaylyk et al. recently reported a new technique, shear-induced polarised light imaging (SIPLI), which combines rotational rheology with a reflection polariscope in order to study the behaviour of macromolecules and nanoparticles through changes in the birefringence properties of a material. Birefringence occurs when there is shear-induced orientation of particles which creates optical anisotropy. Birefringent materials change the orientation of the polarised light used to illuminate the sample, allowing it to pass through an analyser which is orthogonal to the axis of polarised light. The result of shear-induced orientation is a characteristic Maltese cross pattern. Conversely, non-birefringent samples do not change the orientation of plane-polarised light and thus the resulting polarised light image appears dark.

One application for SPILI presented by Mykhaylyk et al., is for the study of thermo-responsive block copolymer micelles. A number of particle morphologies can be produced from the self-assembly of amphiphilic block copolymers in a solvent selective for one of the blocks. These include spheres and vesicles, which form free-flowing liquids, and worms, which form free-standing physical hydrogels. Unlike the non-birefringent nature of the sphere and vesicle morphologies, the uniaxial anisotropy of the worm morphology results in birefringence. Consequently, the thermo-reversible worm-to-sphere transition, and associated reversible de-gelation, of a poly(glycerol monomethacrylate)-block-poly(2-hydroxypropyl methacrylate) hydrogel is an ideal system for SIPLI characterisation.

The rheology data presented in the study confirms the expected reduced viscosity on cooling to 5 °C associated with degelation during the worm-to-sphere morphology transition. Simultaneously, a loss of the Maltese cross pattern is observed due the formation of isotropic spherical particles. On heating, the opposite sphere-to-worm transition occurs resulting in the reappearance of the Maltese cross pattern and an increase in viscosity due to regelation. Here, SIPLI has allowed the study of structural-rheological property relationships of thermo-responsive block copolymer micelles. This demonstrates just one application of SIPLI, with many other advantages and applications of SIPLI discussed in the original article.

Original Article: Applications of Shear-Induced Polarized Light Imaging (SIPLI) Technique for Mechano-Optical Rheology of Polymers and Soft Matter Materials O. O. Mykhaylyk, N. J. Warren, A. J. Parnell, G. Pfeifer and J. Laeuger, J. Polym. Sci. Part B Polym. Phys., 2016, 1–20.

Article by Sarah Byard; a PhD Student on the EPSRC Polymers, Soft Matter and Colloids CDT programme. For more information, please contact Dr Joe Gaunt at the Polymer Centre.