'Molecular ripcord' to kick-start chemical reactions
Researchers at Eindhoven University of Technology (TU/e) in the Netherlands have discovered how to use mechanical forces to control catalytic activity and therefore start chemical reactions - one of the most fundamental concepts in chemistry. This is the first time this has been achieved. The results of the research were published online in the journal Nature Chemistry on 6 April. Chemical catalysts require activation and this is usually achieved by using heat, light or another chemical agent. But a three-strong research team from the Institute for Complex Molecular Systems and the Department of Chemical Engineering and Chemistry, both at TU/e, have demonstrated that a catalyst can be switched from a dormant to an active state by pulling on a polymer chain, thereby making a 'molecular ripcord'. The researchers achieved the result by packing a catalytically active metal ion in two molecular caps (called ligands). Two polymer chains were attached to these caps, creating a long chain with a metal complex in the centre. The researchers then dissolved these in a liquid that was irradiated with ultrasound, which caused bubbles to form in the liquid. When the bubbles imploded, they created a strong current which stretched the chains and then broke the weakest link - the metal complex - in two. This broke the cap from one end allowing the metal ion to become catalytically active, meaning it could begin chemical reactions. This exciting breakthrough will open the way to the creation of self-repairing materials able to strengthen under the effects of physical stress. For example, if a material treated with this method tears, this will break the metal complex and activate the catalyst. This, in turn, would instantly repair the material. The discovery may also lead to research in many other applications where it may be possible to turn chemical reactions on and off. For example, in the injection moulding of plastic objects, the new technique could be used to simplify the processing method. The discovery will also be invaluable in the area of 'green chemistry research'. Being able to control chemical catalysis would mean that scientists can improve the efficiency and yield of chemical transformations and reactions. The researchers say, 'Mechanochemical activation offers new opportunities for homogenous catalysis - a field that will be vital for the development of greener methods of synthesising and processing chemicals. 'Catalysts are ubiquitous in the chemical industry; they are used to make a wide range of different products such as pharmaceuticals and polymer products. Without doubt, the demand for new catalysts will continue to grow.'
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