Rainbows without pigments offer new defense against fraud

Rainbows without pigments offer new defense against fraud
This multicolored image shows the range of colors that can be made by mixing the two block copolymers in varying proportions. Credit: University of Sheffield

Scientists from the University of Sheffield have developed pigment-free, intensely coloured polymer materials, which could provide new, anti-counterfeit devices on passports or banknotes due to their difficulty to copy.

The polymers do not use pigments but instead exhibit intense colour due to their structure, similar to the way nature creates colour for beetle shells and .

These colours were created by highly ordered polymer layers, which the researchers produced using block copoylmers (an alloy of two different polymers). By mixing together, the researchers were able to create any colour in the rainbow from two non-coloured solutions.

This type of polymer then automatically organises itself into a layered structure, causing optical effects similar to opals. The colour also changes depending on the viewing angle. This system has huge advantage in terms of cost, processing and colour selection compared to existing systems.

The complexity of the chemistry involved in making the polymer means they are very difficult for to copy, making them ideally suited for use on passports or banknotes.

The academics used Source, the UK's national synchrotron science facility in Oxfordshire, to probe the ordered, layered structures using high power . This helped them understand how the colours were formed, and how to improve the appearance.

Rainbows without pigments offer new defense against fraud
The banknote picture demonstrates how these colored polymer materials can be made into robust layers that could be used as anti-counterfeit measures on banknotes. Credit: University of Sheffield

Dr Andrew Parnell, from the University of Sheffield's Department of Physics and Astronomy, said: "Our aim was to mimic the wonderful and funky coloured patterns found in nature, such as Peacock feathers. We now have a painter's palette of colours 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 colours required, meaning they can now tailor the polymer composition accordingly."

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More information: To view the paper, 'Continuously tuneable optical filters from self-assembled block copolymer blends', published in Soft Matter, please see: pubs.rsc.org/en/content/articl … g/2011/sm/c0sm01320j

We demonstrate that two symmetric high molecular weight diblock copolymers, of differing molecular weights, can be blended together and subsequently shear aligned to form one photonic structure without macrophase separation. The lameller period depends on the composition of the blend and gives a photonic structure that is easily tuneable in the wavelength range (λpeak = 400–850 nm).

Provided by University of Sheffield
Citation: Rainbows without pigments offer new defense against fraud (2011, May 18) retrieved 18 October 2019 from https://phys.org/news/2011-05-rainbows-pigments-defense-fraud.html
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May 18, 2011
Yep, but the world banks who print the banknotes in the first placeare the biggest frauds of all: new banknotes are not covered by gold or anything else of real value, so it is actually worthless high-tech paper. These worldbanker frauds don't want competition from other frauds, that's all.

May 18, 2011
From what I can tell, it seems like it would be fairly hard to initially replicate the exact pattern. However, it seems like it would be pretty easy to follow the recipe once it had been done.

I think they should try to come up with anti-counterfeit measures that are difficult to replicate every time you do it.

@Koen. This article is not about banks, it's about the process of making paper money.

Monetary value is purely abstract. Gold is just a shiny yellow metal. And there isn't enough of it to float the dollar properly for an economy of our size, regardless of the players involved.

May 18, 2011
Are they really worthless if you work your 40 hours a week for a stack of them? And, by your example, you somehow imply that just because I have a piece of paper that is backed by gold or some other rare commodity that the piece of paper would be impossible to couterfeit?

May 18, 2011
@koen: What is the intrinsic value of gold? It's shiny, I guess, but your assertion that it has "real value" is false.

Money is a idea, representing the trust on the part of the recipient that the value given will be returned eventually. We could exchange animated GIFs as money, it wouldn't matter. What we have learned here is that you (and other gold-standard proponents) do not understand the concept of trust.

May 18, 2011
@matty - Nice call there. counterfeit money is a problem no matter what is backing it.

May 19, 2011
The fact is, your "dollar" is worth 79 cents now compared to that of just 8 years ago. You can't print gold idiots.

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