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Wallace Carothers had helped show that macromolecules could exist. This was what Carothers cared about most, finding the answers to scientific questions. But he did more than simply answer a question. He had created macromolecular materials that behaved a lot like silk. His supervisors at DuPont realized that he was on to something that might prove to be an amazing new material and a new product for the company. Silk was expensive, and most of it came from Japan. Remember that all this was taking place in the 1930s, just a few years before Japan and the United States would be at war in the 1940s. The macromolecules that Carothers had made seemed like a good alternative for silk, and one that would make fortunes for DuPont.
One particular macromolecule was chosen from all the new synthetic polymers that Carothers had created, because it was very strong and easy to make. This polyamide was made by reacting adipic acid and hexamethylenediamine (HMD):
This macromolecule was given the name "nylon 6-6." Count the carbon atoms in the repeat unit and you'll see where the "6-6" comes from. This polymer can be made into very strong fibers for making things such as hosiery, tire cords, and fabric for parachutes. It was an instant hit.
Wallace Carothers made giant molecules out of small molecules in a process is called polymerization. The small molecules from which one makes giant molecules are called monomers. Think of how box cars join together to form a train and you'll get the idea. Lots of different monomers exist, and they can be joined to make thousands of different polymers. The properties of a polymer are determined by its molecular structure, that is, the type of atoms in the polymer, how many of them there are, and how they are arranged in space. Scientists make new polymers with new structures to create materials with desired properties. In the time since Carothers helped prove that polymers are macromolecules, thousands of scientists following in his footsteps have spent time creating new polymers, and there are thousands of stories to be told. Two of them are included in this module. One is about a scientist who looked back to nature, and the other about a scientist who stopped bullets.
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Next: Meet Wallace Carothers