"On the other hand, amides have relatively high
            melting points; and those amides which have been
            prepared from diacid bases (such as benzidine)
            and diacids (such as carbonic) do not melt, but
            decompose at very high temperatures, and are
            insoluble in all solvents."

            -Wallace Carothers,
            -letter to Charles M. A. Stine, 1 March 1928

        When Elmer K. Bolton was placed in charge of the Central Research at DuPont, he expected Carothers and his team to produce useful products for the company. The polyesters they had invented showed promise as a synthetic silk. But they would melt when ironed and would dissolve in dry cleaning solvents.

        The answer to this problem was to use polyamides instead of polyesters. Amides, he knew, had higher melting points than esters and would not dissolve in many solvents. So a polyamide, he figured, would have the heat and solvent resistance he needed to make a good synthetic fiber.

        In the spring of 1934 Carothers suggested to one of his chemists, Donald Coffman, that he should prepare a polyamide, and on 23 May Coffman prepared a polymer called polyamide 9. It melted above 200 oC and didn't dissolve in dry cleaning solvents.

        "By immersing a cold [glass] stirring rod in the
        molten mass upon withdrawal a fine fiber filament
        could be obtained. It seemed to be fairly tough,
        not at all brittle and could be drawn to give a
        lustrous filament."

        -Wallace Carothers
        In July, Wesley R. Peterson prepared an even better polyamide, called polyamide 5-10.

        Peterson accomplished this using a new polymerization technique. Instead of using a mixture of a diacid and a diamine as had previously been done, he used the salt that the diacid and diamine form when they are mixed at room temperature. This ensured that good average molecular weights would be attained.

         

        But polyamide 9 and polyamide 5-10 were expensive to make. A practical polyamide would eventually be made in 1935 by Gerard Berchet.

       

       

          References

          1. Carothers, Wallace to Arthur P. Tanberg. "Early History of Polyamide Fibers", 19 February 1936. Hagley Museum and Library Collection.

          2. Hermes, Matthew. Enough for One Lifetime: Wallace Carothers, Inventor of Nylon. Washington, D.C.: American Chemical Society; Philadelphia: Chemical Heritage Foundation, 1996.

          3. Hounshell, David and Smith, John Kenly. Science and Corporate Strategy, DuPont R&D 1902-1980. Cambridge: Cambridge University Press, 1988, pp. 244-5.

          4. Labovsky, Joseph, DuPont reserach notebook no. 2286.

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