Greener chemistry and new materials with supercritical fluids
We can make the chemical industry greener and safer and produce better, purer products.¯ Professor Steve Howdle, University of Nottingham |
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Professor Steve Howdle helps lead the Clean Technology Group at the University of Nottingham. The group's work revolves around developing sustainable and cleaner ways of manufacturing chemicals and materials, and Professor Howdle's work focuses on finding better, more environmentally friendly alternatives for the conventional solvents that are used in chemical reactions.
New ways to use familiar resources
His aim is to produce greener ways of making polymers plastics and his work is yielding not only purer materials without contamination from solvents or threat to the environment, it also opens the way to entirely new materials. It is all based around a technology that uses a very familiar resource, carbon dioxide ( CO2 ), in an entirely new way.
This technology is based on the properties of supercritical fluids. When carbon dioxide is compressed at pressures greater than 73 atmospheres the distinction between liquid and gas becomes blurred. The result is a supercritical fluid, scCO2, which displays a unique combination of properties. Like a gas, scCO2 has low viscosities and can penetrate materials extremely well. Like a liquid it can dissolve molecules and allow chemical reactions to be carried out.
Supercritical carbon dioxide is so effective at penetrating and mixing with polymers that many liquefy at room temperatures. This allows delicate molecules, which would otherwise be destroyed by heat or react with normal solvents to be mixed into polymers, allowing the creation of entirely new materials.
Cleaner, greener polymer production
These properties can be harnessed in processes that operate at near to room temperature and which provide a particularly pure polymer product which is completely free of solvent residues. Not only is the product cleaner, the production process is greener; simply opening a valve releases the pressure and the carbon dioxide escapes as a gas.
Professor Howdle explains Solvents currently used in plastic production can be highly toxic. Removing those solvents altogether has benefits for everybody. The production process can be cleaner and workers can be safer, the environment is protected and end users can have products without potentially toxic solvent contamination.¯
The potential of replacing conventional solvents, generating zero residues, and producing structurally complex materials all in a single pot without costly interim purification processes represents a significant step forward in green chemistry
A range of applications
There are a number of exciting applications for this new technology. Professor Howdle exploited the fact that biodegradable polymers can be easily liquefied using scCO2. A major breakthrough was the realisation that this could be exploited to develop novel delivery devices to provide controlled release of delicate drugs. This development is already being commercialised through the formation of a spin-out company.
Other applications being investigated include the preparation of scaffolds for tissue engineering, and use of scCO2 to implant metallic nanoparticles in polymers and create new topologically engineered semi-conductors which could revolutionise the electronics industry.
Many other applications are currently being explored. For example, the unique solvent properties of scCO2 surprisingly allow enzymes to function very effectively and these have been used to catalyse the formation of new biodegradable polymeric materials.
Supporting Professor Howdle's work
Professor Howdle holds a Royal Society Wolfson Research Merit award, and began his research with a University Research Fellowship from the Royal Society
