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[I thought I already posted this, so there will be another post "real soon now."]

The terms “plastic electronics” or (electrically) “conducting plastics” probably sound like contradictions in terms. After all, when we commonly think of polymer materials, we think of soda bottles, plastic bags, nylons and other fabrics — all electrical insulators, not electrical conductors. And naturally, when we think of electrically conductive materials, we think of common metals like gold, silver, copper, etc.

And when I began my Ph.D., I certainly thought these terms were contradictory.

One complication with scientific language is that terms are often borrowed from one area to another, and can thus change meaning significantly based on context. So in common usage, “plastics” usually refer to various polymeric materials. Similarly, when we talk about “metals,” we usually refer to a variety of elements like silver (indeed most of the periodic table) are metals — but the term “metal” can also refer to a variety of properties due to high levels of electrical conductivity.

So what makes a good conductor? To have electrical conductivity, you must have mobile, charged particles (usually electrons). Therefore, if you design a polymer which allows electrons to move throughout the material (termed “delocalization”) you’ll have a conductive plastic.

polymers/P3HT.png

Why bother?

Organic chemistry has long been able to tailor the properties of polymers. Think about it — we have plastics of all sorts around us all the time. So for one, electrically conducting polymers offers a new area of flexible, lightweight materials that we can change by synthetic chemistry.

For another, many (though not all) polymers are soluble in a range of typical chemical solvents. This means that we can essentially make “ink” or “paint” or “dye” with a conductive material — and potentially open avenues for inexpensive electronic devices. As an example, some research groups have transformed common inkjet printers to print simple circuits with polymer inks.