This shows the X-ray crystal structure of the 192-atom-loop molecular knot featuring iron ions (shown in purple), oxygen atoms (red), nitrogen atoms (dark blue), carbon atoms (shown in metallic grey, with one of the building blocks shown in light blue) and a single chloride ion (green) at the center of the structure. Image: Robert W. McGregor (www.mcgregorfineart.com).Scientists at the University of Manchester in the UK have produced the most tightly knotted physical structure ever known – a scientific achievement that has the potential to create a new generation of advanced materials.
The University of Manchester researchers, led by David Leigh in Manchester's School of Chemistry, have developed a way of braiding multiple molecular strands to create tighter and more complex knots than had previously been possible. Their breakthrough knot, reported in a paper in Science, has eight crossings in a 192-atom closed loop made up of iron, oxygen, nitrogen, carbon and chloride atoms, which is just 20nm long.
Being able to make different types of molecular knots should allow the scientists to probe how knotting affects the strength and elasticity of materials. This, in turn, will allow them to weave polymer strands to generate new types of materials.
"Tying knots is a similar process to weaving so the techniques being developed to tie knots in molecules should also be applicable to the weaving of molecular strands," explained Leigh. "For example, bullet-proof vests and body armor are made of kevlar, a plastic that consists of rigid molecular rods aligned in a parallel structure – however, interweaving polymer strands have the potential to create much tougher, lighter and more flexible materials in the same way that weaving threads does in our everyday world.
"Some polymers, such as spider silk, can be twice as strong as steel, so braiding polymer strands may lead to new generations of light, super-strong and flexible materials for fabrication and construction."
Leigh went on to explain how he and his team managed to produce the knot. "We 'tied' the molecular knot using a technique called 'self-assembly', in which molecular strands are woven around metal ions, forming crossing points in the right places just like in knitting – and the ends of the strands were then fused together by a chemical catalyst to close the loop and form the complete knot. The eight-crossings molecular knot is the most complex regular woven molecule yet made by scientists."
This story is adapted from material from the University of Manchester, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.