You may think of polymers as entirely manufactured and therefore unnatural, but they are often the chemists’ attempts to supplement and improve on the biological polymers that nature produces. Cotton, ivory, leather, linen, paper, rubber, silk, wood and wool are wonderful materials made from the biological polymers that plants and animals produce, and which have evolved to serve such useful ends as providing protective outer layers, insulation, reinforcement, weaponry and so on. Humans learned that with a little modification they could turn these polymers into quite useful articles, such as briefs and briefcases, condoms and tea cosies, tickets and toothpicks. Sometimes we want polymers with features that never evolved in nature, such as non-cracking insulation for electric cable, clothes that can be unpacked after a long voyage and still be without creases, or pans in which to fry eggs without them sticking. For these polymers we have had to look to chemists. Most of the portraits in this Gallery are of these kinds of polymers—materials that do not have natural equivalents. Polymers are rather special kinds of molecules consisting of long chains, usually made up of carbon atoms, to which other atoms, such as hydrogen, fluorine and chlorine, are attached. The older name for polymers is plastics, and you probably know several of them by name— polythene, polystyrene, Teflon, Orion—but these are only a few of the many that now play an important role in our lives. Whatever role polymers play, they cause many of us to adopt quite strong attitudes towards them. A few of us admire them, many of us ignore them, but a growing number despise them and a few abhor them and will avoid them at all costs. To a chemist, this opposition to polymers seems rather strange. By the time you come to the end of this exhibition I hope that visitors with strong views will have seen enough to persuade them to change their mind. Attitudes towards plastics have changed over the past half-century. In the 19305, when cellophane, PVC, polystyrene, Perspex and nylon were launched, plastics were welcomed.
Symmetric Chain Decompositions of Products of Posets with Long Chains