Polyacetylene conductive polymers

The class of materials at issue in the Wennick talk; now used for touch screens, never displaced copper.

People can use those phrases all the time, and they do that for the unaware. You should not be the unaware — you're MIT grads or soon will be. I was sitting in the old Shipman room, probably 20 or 25 years ago. A young professor, Gary Wenick, was in polymer science. This was at a time when people had just discovered things like polyacetylene, which were electrically conductive polymers. He was giving a talk to the visiting committee or somebody about his research. He said, these conductive polymers have a specific electrical conductivity — that means the electrical conductivity, which is the inverse of resistance, divided by the density — that is better than copper.

A young professor's claim that polyacetylene would replace copper because of higher *specific* electrical conductivity. Tom's shaving-mirror realization the next morning: aluminum already has higher specific conductivity than copper, but we don't use it in rotating machinery — because absolute conductivity is what matters, not specific.

About thirty years ago I was sitting in what was the Chipman Room back then, listening to a talk from a new young professor who was working on electrically conductive polymers. Anybody familiar with electrically conductive polymers? The first one that came out was polyacetylene. These are polymers with lots of double bonds, so they have some free electrons, which means they can be electrically conductive. The only problem is they tend to decompose in air — the humidity in the air and so on. But they're very light, and he mentioned something I'd never thought about before. He said these were going to be the material of the future, they were going to replace copper, because the specific electrical conductivity of polyacetylene and these new electrically conductive polymers was less than that of copper. And copper is the electrical conductor we use in general.

Another thing people do with new materials is they'll be very careful about how they phrase the properties. The example I like to give was Professor Gary Wnek, who was an assistant professor in this department. He left before tenure ever came. He was really a chemist but he worked on polymers. This was back 25, 30 years ago when electrically conductive polymers were a new thing. He was giving a talk in the Chipman Room about his research on electrically conductive polymers. At the time the polymer was polyacetylene. Ordinarily polymers are covalently bonded — there's no free electrons, and that's why they're excellent insulators. Polyacetylene has a bunch of double bonds, and so properly doped, it can have some free electrons and so is electrically conductive. He was pointing out that the specific electrical resistivity of polyacetylene was better than copper, and therefore big rotor generators and rotating machinery and motors would all be using polyacetylene or other conductive polymers in the future. I thought, wow, that's pretty impressive.