Novel monomers from sugars: synthesis, catalysis, polymerisation and applications in degradable electronics

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The topic of research for this PhD will be the synthesis of novel degradable polymers sourced from sugars and their applications in energy applications, namely battery technology. Currently, mainstream lithium-ion batteries (LIBs) as well as new generation batteries rely on aqueous electrolytes to transport cations between the electrodes. These types of batteries pose serious safety concerns for a number of reasons. On the other hand, solid polymer electrolytes (SPEs) are a promising class of alternative electrolyte materials which can offer high mechanical strength, flexibility and a lower cost than other solid electrolytes such as ceramics.Polyethylene oxide (PEO) has been heavily studied as a SPE material and the model for the ionic conductivity of PEO is well understood. However, whilst PEO is a good conductor of lithium ions, it does have some limitations that means it will not be a suitable material in any realistic future battery applications. In order to develop future SPE-based batteries, novel materials are needed which can improve upon the properties of polymers such as PEO.Polycarbonates have been shown to be a promising class of polymers for SPE materials with the potential for high ionic conductivity. They can also be sourced from natural feedstocks and have the advantage of biodegradability for their end of life. However, polycarbonates can be difficult to functionalise and therefore difficult to tune for desired properties.The Buchard group already has a platform of sustainable polycarbonates made from the reaction of CO2 with renewable diols from sugars. These polymers also have alkene functionalisation in the carbon backbone with the potential ideal for developing novel biodegradable SPE materials from renewable feedstocks. This research will look to assess the lithium-ion conducting capabilities of these polymers with varying degrees of crystallinity, molecular weight, cis/trans ratios of the alkene, etc. The alkene bond will also be functionalised (post-polymerisation) to incorporate lithium-coordinating groups and/or any other functional groups which will provide the polymer with properties ideal for SPEs. Moreover, the replacement of oxygen with sulfur in the carbonate moiety, giving monothiocarbonate and xanthate monomers, will also be explored as a way to access better polymer properties for SPE materials.Following the successful synthesis of novel polymers, rigorous mechanical and physicochemical characterisation will be performed, for which multinuclear NMR, mass spectrometry (MALDI), Size-Exclusion Chromatography (SEC), Differential Scanning Calorimetry (DSC), X-ray scattering and stress/strain tests will be important techniques. Electrochemical characterisation of the polymers with lithium salts will then be investigated, in collaboration with Prof F. Marken (second supervisor at Bath), via ionic conductivity and cyclic voltammetry measurements. Promising materials will be put forward in the construction of real coin cell devices in collaboration with Prof D. Mercerreyes (Basque Center for Macromolecular Design and Engineering, Spain). The application of our new polymers as SPE materials will be tested in LIBs but also in other promising battery types, such as Li-S and Na-ion batteries. Other energy applications will also be considered, such as the functionalisation of the alkene bond with conducting organic motifs for the synthesis of novel polymers for uses in organic photovoltaic devices. This work will have the potential for collaboration with Dr H. Bronstein in Cambridge.