The polymer materials can be made into robust layers that could be used as anti-counterfeit measures on banknotes. |
Scientists from the Univ. of Sheffield
have developed pigment-free, intensely colored polymer materials, which could
provide anti-counterfeit devices on passports or banknotes.
The
polymers do not use pigments, but instead exhibit intense color due to their
structure, similar to the way nature creates color for beetle shells and
butterfly wings.
These colors were created by highly ordered
polymer layers, which the researchers produced using block copoylmers. By
mixing block copolymers together, the researchers were able to create any color
in the rainbow from two non-colored solutions.
This type of polymer then automatically organizes
itself into a layered structure, causing optical effects similar to opals. The color
also changes depending on the viewing angle. This system has huge advantage in
terms of cost, processing, and color selection compared to existing systems.
The complexity of the chemistry involved in
making the polymer means they are very difficult for fraudsters to copy, making
them ideally suited for use on passports or banknotes.
The academics used Diamond Light Source, the UK’s national
synchrotron science facility in Oxfordshire, to probe the ordered, layered
structures using high power x-rays. This helped them understand how the colors
were formed, and how to improve the appearance.
Dr Andrew Parnell, from the Univ. of Sheffield’s
Department of Physics and Astronomy, said: “Our aim was to mimic the
wonderful and funky colored patterns found in nature, such as Peacock feathers.
We now have a painter’s palette of colors that we can choose from using just
two polymers to do this. We think that these materials have huge potential to
be used commercially.”
Professor Nick Terrill, Principal Beamline
Scientist for I22, the Diamond laboratory used for the experiment, explained:
“Small Angle x-ray Scattering is a simple technique that in this case has
provided valuable confirmatory information. By using Diamond’s x-rays to
confirm the structure of the polymer, the group was able to identify the
appropriate blends for the colors required, meaning they can now tailor the
polymer composition accordingly.”
