Rainbows without pigments
15 Jul 2011 by Evoluted New Media
Using just two polymers, scientists in Sheffield have created a new generation of anti-counterfeit devices that prove difficult to copy.
Using just two polymers, scientists in Sheffield have created a new generation of anti-counterfeit devices that prove difficult to copy.
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Dr Parnell wanted to mimic natures funky colours |
Scientists from the University of Sheffield have developed intensely coloured polymers which are pigment-free. Colours are created by mixing together just two block copolymers – an alloy of two different polymers.
This type of polymer automatically organises itself into layered structure, causing an optical effect similar to opal, with the colour changing depending on the angle you look at it from. By mixing the block copolymers together in varying proportions, the researchers were able to create any colour of the rainbow.
“Our aim was to mimic the wonderful and funky coloured patterns found in nature, such as peacock feathers,” said Dr Andrew Parnell from the departments of physics and astronomy. “We now have a painter’s palette of colours we can choose from using just two polymers to do this.”
The scientists travelled to Diamond Light Source in Oxfordshire to study their ordered, layered structures using high power x-rays on the I22 non-crystalline diffraction beamline. The synchrotron helped them understand how the colours were formed and how to improve their appearance.
“Small Angle X-ray Scattering is a simple technique that has provided valuable confirmatory information,” said principal beamline scientist on I22, Professor Nick Terrill. “By using Diamond’s x-rays to confirm the structure of the polymer, the group was able to identify the appropriate blends for the colours required, meaning that they can now tailor the polymer composition accordingly.”
The complex chemistry involved in making the polymer means they are very difficult to fraudsters to copy – making them ideally suited for used on passports and bank notes.
“We think that these materials have a huge potential to be used commercially,” said Parnell.
Check out the colour-shifting properties of the polymers in the video Colour-shifting ink under Lab News Recommends at www.youtube.com/labnews
