Catalysis and Materials Chemistry
My research interests include the study of metal complexes for use as homogeneous catalysts to make polymers, fuels and materials. I am motivated to discover how to use and recycle renewable resources, such as plants or carbon dioxide, to make useful products such as polymers. In the area of inorganic chemistry, research in my group includes the preparation of new metal complexes, their use in homogeneous catalysis, uses of in situ spectroscopy for catalyst characterization and analysis of the reaction kinetics. Recently discovered catalysts include complexes of transition metals, lanthanides and main group elements. Furthermore, we have recently investigated a series of colloidal nanoparticles, comprising Cu/ZnO and other metals, as catalysts for the production of methanol and other liquid fuels. Some common themes of all catalysis research in my group are to apply earth-abundant and cost-effective metals; to develop efficient processes and to maximise selectivity and control so as to produce valuable products. Polymer chemistry research in my group involves polymer preparation, exploration of materials’ properties and assessments of future applications. We are particularly interested in new oxygenated polymers, such as polyesters/carbonates, and in developing methods to prepare, re-use and recycle polymers as products from bio-refining, industrial wastes and biomass so as to improve sustainability. In collaboration with other research groups worldwide, the new polymers have been evaluated for applications including as rigid plastics, elastomers, coatings, fibre-reinforced composites, matrices for tissue engineering, antimicrobial surfaces and as self-assembled nanostructures in controlled release.
The Williams Research Team
Our group is diverse, international and multi-disciplinary and we collaborate with other experts worldwide across a range of fields. The Williams team have expertise in areas including inorganic chemistry, organic chemistry, catalysis, polymer chemistry, materials science and chemical engineering.
Williams Research Group, Oxford, 2019
Research Group Website
My research focusses on new sustainable technologies for polymer production and carbon dioxide usage. My team develop highly active catalysts that transform abundant renewable resources and wastes into polymers. These catalysts enable natural bio-chemicals and carbon dioxide to replace petrochemicals in scalable materials production. Recent discoveries include bimetallic, synergic catalysts for low-pressure carbon dioxide copolymerisations; switchable polymerisation catalysis using monomer mixtures to produce new polyesters, -carbonates and -ethers; iso-selective lactide ring-opening polymerisation; colloidal nanocatalysts for carbon dioxide hydrogenation and high performance sustainable polymers. By combining expertise in catalysis and polymer chemistry, our objective is to deliver materials with better properties than today’s petrochemicals and which are designed for end-life recycling and (bio)degradation. More details on our research and publications are found on the group webpages and only an overview is presented here.
1) Carbon dioxide copolymerisations
Our catalysts show high activity, selectivity and control in carbon dioxide/epoxide copolymerisations to make polycarboantes. These polymers are 30-50 wt% comprised of carbon dioxide enabling a triple win in reducing greenhouse gas emissions– for every molecule of carbon dioxide used, two more are saved by avoiding petrochemicals. The polymers have properties well-suited to applications including as polyols, coatings, resins and ductile plastics. Our catalysts comprise earth-abundant and inexpensive metals such as Zn(II), Mg(II), Na(I) and Fe(II/III) and we have pioneered synergic heterodinuclear catalysts. In 2020, we proposed the molecular basis for synergy, rationalizing the different roles for the two metals.
2) Switchable Polymerisation Catalysis Using Monomer Mixtures to Make Ordered Multi-Block Polymers
We have developed a form of switchable polymerisation catalysis whereby a single catalyst selectively transforms monomer mixtures, accessing different polymerization cycles, into specific block polymer sequences. We uncovered the ‘rules’ determining monomer enchainment; these rules are generally applicable to other metallic, organometallic and organo-catalysts and to many monomers. The switchable polymerization catalysis efficiently and quantitatively yields new types of multi-block polyesters,-carbonates and ethers. We use it to make tough and ductile carbon dioxide-derived plastics, strong bio-derived pressure sensitive adhesives and high elasticity thermoplastic elastomers.
3) Isoseletive Lactide Ring-Opening Polymerisations
Polylactide (PLA) is a commercial bio-derived plastic made from sugar and after use can be composted, biodegraded and or fully recycled. Controlling PLA stereochemistry is one way to improve properties, isotactic or stereoblock PLA shows a high melting temperature and tensile strength. We have investigated phosphasalen Group 3, 13 and lanthanide catalysts which combine high activities, low loadings, good control and high iso-selectivity. In collaboration with Paul Beer’s research team we discovered molecularly-interlocked rotax-2-ane iso-selective catalysts.
4) Sustainable Plastics and Elastomers
We develop controlled catalyses to make precision polyesters,-carbonates and ethers, maximising renewable resource usage. These polymers improve upon the petropolymers’ properties and are recyclable and biodegradable. Some are catalytically depolymerized to true monomer(s) whilst others are fully degraded using solvolyses. Through close collaboration with scientists and engineers, in academic and industrial laboratories, we are studying their use as commodity plastics, elastomers, coatings, specialities/additives, composites, solution self-assembled nanostructures, in formulations, medicine and soft robotics.
5) Colloidal Nanocatalysts for Carbon Dioxide Hydrogenation
Working with Milo Shaffer (Imperial College London), we make well-defined, ultra-small ZnO, ZnS, Cu, Cu2O and Cu2S nanoparticles from organometallic reagents. Using sub-stoichiometric quantities of ligands, such as carboxylic/phosphinic acids, yields high solubility colloidal nanoparticles. ZnO/Cu nanoparticles are high activity and selectivity solution catalysts for carbon dioxide hydrogenation to methanol.