This is the third book in the series that included 'The Theory of Nothing' the "The Universe Revealed.' My purpose in this new book is to more fully explain how science is actually done and how science fits into our culture along with religion and p...
Polymers are the wonder of the modern world. Most people don't think about them, but they are in many things that we wear, use and have in our cars, furniture and electronic devices. The first question is: what is a polymer?
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A polymer is a molecule that contains many (poly) repeated subunits. Essentially, a polymer is a long chain molecule made up of relatively simple units connected together. They are mostly the synthetic plastics. Examples include: Polystyrene, Polyvinyl chloride, Polyethylene, Polyacrylonitrile, etc. There are many other natural or semi-synthetic polymers like cellulose, silicone, neoprene, silk, etc. In this essay I want to discuss only synthetic plastics.
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How are polymers synthesized? The method of creating a polymer is called polymerization. One starts with a monomer and then reacts it with a catalyst that promotes polymer formation, essentially forcing the monomer units to combine into a long chain. In many cases heat is used to promote the polymerization reaction. There are many ways to conduct polymerizations. Let's just say it's mostly chemistry.
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You could think of it this way. Let's say you want to make a long beaded necklace, but instead of stringing the beads on a string or wire you tie the beads together one by one, adding beads to the group of tied beads until you get the required length. This is the way polymerizations are usually done.
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Many of these reactions use free radicals, which are molecules that have an atom with only one free electron. Free radicals can be created by splitting a molecule that has an oxygen-oxygen bond or a nitrogen-nitrogen bond using heat or UV light. For example one could take a persulfate, which is two units of a sulfur atom with four oxygen atoms connected to it, and heat it. Heat splits the two sulfate units to create a reactive radical.
The end result of a polymerization is a long chain molecule with many repeating chemical units. So, how do they know how many units are in a polymer chain? That's a good question. It turns out that the melting and boiling point of a polymer increases with chain length. Also, the impact resistance and viscosity also increase. The easiest method is to determine the melt viscosity of a polymer, especially if it's a plastic. Melt viscosity is related to chain length as n - Z to the 3/2 power. The rough rule is that a tenfold increase in chain length results in a viscosity increase of 1000 times. This is the power of polymerization. One can create very high viscosities easily. Polymers have excellent solvent and heat resistance. Some can even be made as strong as steel. They are truly the miracle molecules of modern science.
This is only a rudimentary discussion of very complicated subject, but it's very important to realize how plastics and other polymers play a part in our lives.
