Synthesis of Organometallic Catalysts for Switchable Polymerisations Using Renewable Resources: Next Generation Sustainable Elastomers and Engineerin

Lead Research Organisation: University of Oxford
Department Name: OxICFM CDT

Abstract

Plastics are some of the most important materials we encounter in our everyday lives. From packaging to our clothes and our beloved electronic devices, plastic materials have become a cornerstone of modern society. These plastics are made up of a type of molecule called polymers. Polymers are long-chain molecules made up of lots of smaller building block molecules known as monomers. Both the type of monomers used and the order they are connected together in determine whether a plastic is hard or soft, brittle or tough. Therefore, chemists can control the properties of a polymer by deciding which monomers to include in the chain and how they are arranged. This allows for the creation of different plastics for various applications.
The majority of plastics we use are made up of monomers that are sourced from fossil fuels and are therefore unsustainable. Petrochemical derived polymers are also able to remain in the environment for incredibly long periods of time without degrading and the pollution they cause as a result can have potentially fatal consequences to many living organisms. This has led chemists to explore the possibility of making biodegradable polymers from bio-derived resources such as plant extracts or even carbon dioxide, the gas primarily responsible for global warming.
Unfortunately, polymers made of only one of these sustainable monomers have poorer mechanical and thermal properties compared to their fossil-fuel derived cousins. However, it has been shown that combining two or more bio-derived monomers together can result in the production of plastics with impressive properties. One option is to achieve these property improvements through the formation of block copolymers. These are a type of polymer containing chemically distinguishable segments of monomers that are joined together in one chain. In 2014, a new method of making sustainable block copolymers was discovered called switch catalysis. This new discovery allows for block copolymers to be produced easily and with a precise sequence of monomers.
Switch catalysis has since been used to produce a range of different sustainable polymers with better properties than either of the constituent blocks. However, if these new sustainable plastics are to truly compete with their petrochemical counterparts, new chemical strategies are still needed to make a broader range of materials and to improve the efficiency of the manufacturing process.
This project will investigate both the property improvements and the catalysis used to make them. In the first phase, a series of chemistries allowing for the modification of existing sustainable plastics made using switch catalysis will be explored. By introducing a small volume fraction of inexpensive and earth-abundant metal ions, it may be possible to network the polymer chains and provide further structural rigidity. These new materials are called ionomers and currently the potential for biodegradable ionomers is not well understood but this will be addressed through the current investigation.
This project falls within the EPSRC 'manufacturing the future' research area and will involve collaboration with the department of engineering to test the new types of plastic produced. The strength, toughness, stiffness and elasticity of all the materials will be compared within systematic series of polymers, ionomers and networks. These ionomers should also display the ability to self-repair or heal in the event of cracking or snapping due to the reversible nature of the polymer-metal bonds. Furthermore, unlike traditionally cross-linked polymers, such as rubber, it should be feasible to reprocess and recycle these materials. The self-healing behaviour and recycling potential will also be investigated in this project.
The overall goal is to deduce efficient manufacturing routes to bio-derived, recyclable and biodegradable products showing excellent mechanical properties and which may help improve sustainability of plastics

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/S023828/1 01/04/2019 30/09/2027
2404175 Studentship EP/S023828/1 01/10/2020 30/09/2024 Kam Poon