Material degradation is a primary concern to every material scientist and engineer, not only does degradation lead to failure, but results in the need for repair - a very costly endeavour. In this perspective, it is of interest to develop self-healing materials that will make maintenance redundant. As opposed to inorganic semiconductors, organic semiconducting materials are soft, which makes them ideal to be used in flexible and stretchable electronic devices, which can be directly applied to the human skin. Wearable electronics, however, are particularly prone to mechanical damage and fatigue, which is why it is paramount to develop more robust materials, like self-healable semiconductors. This fellowship will, for the first time, make it possible to synthesise intrinsic self-healing organic semiconductors and incorporate them into fully flexible, stretchable and wearable electronic devices, respectively bionic skin, to measure biological metabolites associated with diabetes (glucose), fatigue (lactate) and stress (cortisol). The electric charges will be transported via the conjugated polymer backbone, while additional supramolecular functionalities (i.e. non-binding interactions) will be incorporated into the chemical structure to ensure self-healing via the formation of dynamic bonds. The study of the new self-healing polymers will then be extended to other dynamically bonding functional groups to evaluate which chemistry is best suited for organic semiconductors. Subsequent steps will focus on the self-healing dynamics and rates, and the incorporation of the new materials into flexible electronic prototype devices. The realisation of healable organic semiconductors, for the first time, will allow the fabrication of lightweight, -wearable sensors directly applied to the human skin. This will make it possible to continuously monitor medically relevant body functions and present a significant step forward in the development of affordable biological sensors and continuous patient monitoring, ultimately enhancing medical diagnostics and opening-up new treatment possibilities.

There is an urgent need to devise processes for recycling plastics, with an estimated 460 million metric tonnes of plastics being utilised worldwide in 2019 alone, of which only 10% is recycled globally, the remainder going to incineration, landfill or export. Burning of polymers contribute to CO2 production, causing global warming, and pollution of rivers and oceans occurs through discarding to the environment. Current mechanical and thermal recycling techniques can be used to produce lower grade products such as clothing, insulation, garden and road furniture, but these have inferior colour or mechanical properties, in comparison to virgin polymer, necessitating chemical recycling to produce virgin monomer. The principal polymer selected for study in this proposal is PET, with its wide industrial and consumer applications in bottles, packaging and clothing. In the USA 30 % of PET is currently recycled, in the EU the figure is 52 %, whilst world demand for PET resin is ~23.5 million tonnes and production capacity ~30.3 million tonnes, making a potentially large feedstock for recycling. Virgin PET resin has a much higher value at £1084/tonne compared with used PET bottles priced at £222.50/tonne, making chemical recycling to produce the virgin polymer the more economically attractive route than mechanical or thermal recycling. Chemical recycling of PET can follow a number of routes including reaction with alcohols, glycols, amines and ammonia, sometimes catalysed by basic materials like sodium bicarbonate, or more recently developed ionic organocatalysts or metal salt/organic base dual catalysts. However potential scale up for industrial production is hampered by the difficulties of separating the catalyst from the product mixture and efficient recycling. Also, there is a need to isolate and purify the product BHET from a mixture which may contain contaminants from the polymer, including dyes and additives. This proposal aims to create solutions to these problems by developing supported catalysts and separation technologies to enable a scaled-up process for PET depolymerisation, which could potentially be deployed industrially. Catalyst supports will be developed based on thermally responsive polymers, which can be solubilised to contact the reacting mixture, or solidified via simple temperature cycling to aid recovery by filtration. Key considerations will include understanding the reaction kinetics of the system, including any mass transport resistances, and optimisation of reaction conditions to achieve an attractive rate of reaction. We will experiment with polymer structures to find the optimal catalyst/support combination. In addition to catalyst recovery by temperature cycling, we will study recovery of BHET product via membrane separation. Strategies will include testing of commercial membranes and development of mixed matrix membranes incorporating zeolites to enhance the permeate flow. The proposed technologies will provide more attractive and commercially viable solutions for chemical recycling. In order to realise the benefits of the research, we have engaged Project Partners from across the recycling and polymer production sectors including Dupont Teijin Films and Siemens PSE, and academic collaborator Pennsylvania State University. They will provide, or advise on, samples for depolymerisation, provide software, technical consultation on the work plan, access to facilities and advise on routes to commercialisation and impact delivery as outlined in their letters of support.

We propose to mitigate the transmission of COVID-19 between humans by development of antiviral formulated products. It will be delivered via additives in domestic formulated products, e.g. spray or aerosol, or integrated with current manufacturing processes, forming an invisible and long-lasting film of sub-micron thickness. Unlike disinfectants, formulations will be designed to both capture the aerosol droplets and inactivate the virus. Our first priority is to establish a mechanistic understanding of the interactions between aerosol droplets (or pure virus particles) and surfaces, which will inform possible antiviral mechanisms while providing a set of fundamental and coherent design principles for antiviral surfaces. Two technology platforms will be pursued to leverage the expertise and capability of our industrial partners. Polymer additives with controlled chemistry and molecular architecture will be explored to generate molecular films that facilitate disruption of aerosolised droplets and which may rupture the viral envelope or interfere adversely with key viral proteins and or genetic material. Proposed nanocellulose additives will confer additional benefits in terms of providing a porous structure designed to wick and absorb any protective mucus present. In parallel, hybrid polymer technology will be developed, employing reactive oxygen-producing copper nanoparticles coupled with flavin dyes that produce singlet oxygen species known to deactivate viruses when irradiated with light of the appropriate wavelength. Upon satisfactory antiviral testing results, promising design/formulation will be recommended based on their processability, suitability for end-applications, and environmental impact. Industrial partners with substantial experience in formulation will carry out pilot-scale production and full- scale manufacturing subsequently.

There is an urgent need to devise processes for recycling plastics, with an estimated total of 8300 million metric tonnes of plastics produced to date, of which less than 10% have been recycled overall. The end fate of polymers can include landfill, burning which contributes to CO2 production, global warming, and discarding into the environment, including rivers and oceans. Of the materials which are recycled, mechanical or thermal recycling techniques typically produce a lower grade of polymer which can be used in applications such as clothing, insulation, garden and road furniture for example, and also has inferior properties (e.g. colour and mechanical specification) and value compared with virgin polymers. PET is selected as the principal polymer for depolymerisation studies in this proposal, owing to it being widely used, with typical applications in clothing, bottles and packaging. The world demand for PET resin is ~23.5 million tonnes and production capacity ~30.3 million tonnes, whilst only 30 % (US) - 52 %(EU) is currently recycled. However used PET bottles are priced £222.50/tonne whilst virgin PET resin is priced £1084/tonne, making a strong economic case for chemical recycling to produce the virgin polymer, rather than mechanical or thermal recycling to a lower grade product. Chemical recycling of PET can be achieved via methods such as alcoholysis, aminolysis, ammonolysis and glycolysis, including via catalytic methods such as ionic organocatalysts. Some drawbacks of currently available recycling methods such as glycolysis involve the separation and eradication of contaminants such as catalyst residue and dyes from the product, difficulty of separating the project BHET from the reaction mixture in case it repolymerises during vacuum distillation and requirement for high purity PET feed to make high grade recycled products. This proposal aims to address these drawbacks by developing a scalable, continuous process for PET depolymerisation. In particular we aim to study the effect of polymer additives and food contaminants in real wastes upon the depolymerisation, to understand how the catalyst/process can be made resilient to these issues. Key considerations will be to fully understand reaction kinetics, enabling catalyst immobilisation to enable recycling of it and developing strategies for product recovery. The proposed technologies are expected to deliver potential benefits including reduced reliance on fossil derived virgin plastics, potential to increase the market for chemically recycled polymers, and deliver of a scalable process. We have engaged Project Partners from across the recycling, polymer production and academic sectors including Suez, Avantium, Dupont Teijin Films, Process Systems Enterprise and University of Liverpool. They will provide or advise on samples for depolymerisation, catalyst supports, provide technical consultation on the work plan and advise on routes to commercialisation and impact delivery as outlined in their letters of support.

This project is centred on the development of the materials, device structures, materials processing and PV-panel engineering of excitonic solar cells (ESCs). These have the potential to greatly reduce both materials and also manufacturing costs where the materials, such as organic semiconductors, dyes and metal oxides, can be processed onto low-cost flexible substrates at ambient temperature through direct printing techniques. A major cost reduction is expected to lie in much-reduced capital investment in large scale manufacturing plant in comparison with conventional high vacuum, high temperatures semiconductor processing. There are extensive research programs in the UK and India developing these devices with the objective of the increase in PV efficiency through improved understanding of the fundamental processes occurring in these optoelectronic composites. However, there has been less activity in the UK and India on establishing from this science base a scalable, commercially viable processing protocol for excitonic solar cells. The scope of this UK-India call enables research and development to be undertaken which can pull together the set of activities to enable manufacturing application, and this extends beyond the usual scope of funding schemes accessible to the investigators. This project tackles the challenge to create cost-effective excitonic solar cells through three components: new material synthesis of lower cost materials; processing and development of device (nano)architectures compatible with low process costs; and the scale up towards prototypes which can replicate solar cell performance achieved in the research phase. The team includes leading scientists in the UK and India working on excitonic solar cells. Skills range from material synthesis and processing, device fabrication and modelling, wet processing of large area thin films, and PV panel manufacture and testing. Careful consideration has been made to match and complement the skills on both sides of the UK-India network. Further to this, engagement with industrial partners in both the UK and India will allow access to new materials, substrates etc., and access to trials and testing of demonstration PV panels in the field.