Melanin---the First High-Conductivity Organic Polymer ?

"For the discovery and development of conductive polymers" Nobel Citation.

A Nobel imprimatur defines the history of discovery, rightly or wrongly. There are two issues. 2) A high conductivity organic polymer and 2) The first organic electronic device.

First, the first high conductivity polyacetylene-derived organic polymers were reported by Bolto et al.

However, we reasonably believe we reported the first organic active electronic device. If anyone knows better, please inform us. Thus, our organic semiconductor device gadget is now in the Smithsonian chips collection of the American Museum of History. Likewise, the active element in nearly all such subsequent devices is also technically "melanin", a synonym for polyacetylene and its derivatives. For a summary see this Review from IBM.

But was our device equivalent to Shirakawa, Heeger, and MacDiarmid's later discovery of a high-conductivity form of polyacetylene ? It depends on how you define this. Again, melanin is a polyacetylene and vice versa. Thus, as referenced in the Nobelist's patents, an older name for such compounds is acetylene, aniline, etc., "blacks". Similarly, both parties explained conduction in our compounds the same way--- phonon-assisted hopping, mobility gaps, etc.. That is, the science is the same.

So, simply-stated, the basic difference between our work and that of Shirakawa et al(1) is that they used chemical "doping" to produce a high conductivity state in one melanin, while we used an electric field to produce a similar result in another. That is, we made an active device, a bistable switch. Our priority claim arises because the "on" state of this switch has high, "metallic", conductivity.

This was well-appreciated at the time--- e.g, a Nature "News and Views" article , from April 5, 1974. Here Nature's "Solid State Physics Correspondent" emphasizes our material's " strikingly large conductivity", " highly conducting state " and " large conduction " .

So what happened ?

Though the Nobel Foundation spends about 60% of its budget to prevent such errors, they clearly missed our earlier work. For example, the citation implies that Shirakawa et als' 1977 paper (1) was the first demonstration of a highly-conductive organic material and that this eventually lead to the first organic electronic devices.

So, they missed our 1974 report of both such an electronic device and an incidental highly conductive state in melanins. Likely, had the committee considered our prior art, they would have worded the award citation more narrowly to exclude our discoveries.

Similarly, the primary reason given for the Nobel Award is that the winner's work led to the (re)discovery of active organic devices. Our claims to prior discovery of a highly-conductive organic polymer aside, would the Nobel committee have made this award had they known of any prexisting device ?

Science and Nature are not obscure journals. This eliminates a major cause of Nobel "misses" and of citation failures. Likely, in 1974, a conductive organic polymer and an organic electronic device seemed a sui generis oddity. Similarly, the generation of physicists ( such as Neville Mott* ) who knew of it passed. Meanwhile, the field went through the "bottleneck" of the eventual winner's work, which never cited our prior art.

This lack of citation is puzzling, since a prior high-conductivity form of any organic polymer is obviously relevant, as is an organic electronic device. Even more astounding, our device involved the same chemical class as theirs and most later such devices. Similarly, following their first battery patent, one of us ( JM ) tried to contact Heeger and MacDiarmid, but gave up because of no response.

Arguably, this is "Disregard Syndrome"(2,3). This can be quite inadvertant and involve things as simple as a name change. For example, had we as correctly titled our paper " Amorphous Semiconductor Switching in a copolymer of Polyacetylene, polyaniline, and polypyrrole ", the connection would have been clearer. Similarly, both parties have patents for much the same thing ( e.g., batteries ) and are cited in a patent for another organic battery.

Interestingly, many of their later general patent claims are essentially identical with our "prior art". For example, the two McGinness patents ( 4,366,216 and 4,504,557 ) tacitly involve the following items: 1) the reversible reduction and oxidation of a 2) doped, 3) conductive, 4) zwitter-ionic, 5) redox polymer with 6) carboxyl and/or sulfonyl groups in a 7) protic solvent such as water or alcohol.

In a striking example of convergent discovery, these are also key general claims in later Heeger and MacDiarmid patents and part of the "development" in the Nobel citation. The denial of these general claims because of our prior art would have severely limited the scope of their patents. E.g., the "protic solvent" makes possible practical batteries and greatly extends the range of possible materials and devices. The Bronsted acids, etc. make a polymer "self-doping" ( which melanin is ), etc.

That is, their original Nobel-winning discovery was a dead-end because of its instability and lack of usefulness. By convergent invention, Shirakawa et al eventually ended up with materials and technology rather like ours.

Specific examples include MacDiarmid's EP0131829** ( "Polymer Batteries and Fuel Cells having Protic Solvents and Methods for their construction and use" ) and Heeger's US5569708 ( "Self-Doped polymers" ), as well as many of their other patents. Even some minor details are similar. E.g., we used diethyamine as a dopant, they use methylamine, etc.. Similarly, McGinness et al '557 claims carbonizing a conductive polymer ( "..or formed by graphitization upon heating..." ) as does Shirakwa JP2001172369 ( " Carbonized Polymer Material and its production method " ).

This likely just reaffirms that inventors are secondary and that the discovery is the thing. When the time is right ( in this case, following the characterization of conductive mechanisms in disordered materials ), inventions essentially invent themselves. But this is a distinct issue from a viable scientific cursus honorum. Here, discovery credit plays an important part, however trivial it may be otherwise.

Ironically, while we played with it, we considered increasing melanin's conductivity by doping of little import compared to a true electronic device. Drawing upon the work of others such as George Cotzias, we had even previously noted that doping of melanin by charge-transfer agents ( including iodide and transition-series matals ) might modulate its conductivity. Some melanins even emit a flash of light as they switch, implying possible electroluminesence.

Peter H Proctor, PhD, MD

1) C. K. Chiang, C. R. Fincher, Jr., Y. W. Park, A. J. Heeger , H. Shirakawa, E. J. Louis, S. C. Gau, and Alan G. MacDiarmid, Electrical Conductivity in Doped Polyacetylene, Phys. Rev. Lett. 39, 10981101 (1977).

2) Isaac Ginsburg "The Disregard Syndrome: A Menace to Honest Science?" The Scientist 15[24]:51, Dec. 10, 2001

3) Barry A. Palevitz, "The Ethics Of Citation: A Matter Of Science's Family Values", The Scientist 11[12]:8, Jun. 09, 1997

*Physics Nobelist Nevel Mott, correctly identified melanins ( and thus electrically-active polyacetylenes in general ) as " So like and yet so unlike the chalcogenide switches ".

** Interestingly, EP0131829 ( a European patent covering much the same material as the McGinness patents ) has a US priority date. That is, the initial application was to the US patent office. However, apparently no US patent issued, nor is there a continuation in part or the application withdrawn ( say, to resubmit in another application ). Most likely, the patent office rejected this patent and any appeals failed.

Because the "file wrapper" is not available for older unissued patents, we can only speculate why (or even if) this patent application was rejected. Obviously, the invention has "utility" and "non-obviousness". So the rejection was likely for "lack of novelty", i.e., prior art.

At this time, the only published works in this area were our patents and those of the eventual winners. Perhaps the patent office cited our prior art as cause for rejecting the Noble winners patent. The implications of this on the relationship between our work and the "development" part of the Nobel citation are left to the science historians.

Power structure of science