Polymers are substances made up of recurring structural units, each of which can be regarded as derived from a specific compound called a monomer. The number of monomeric units usually is large and variable, each sample of a given polymer being characteristically a mixture of molecules with different molecular weights. The range of molecular weights is sometimes quite narrow, but is more often very broad. The concept of polymers being mixtures of molecules with long chains of atoms connected to one another seems simple and logical today, but was not accepted until the 1930's when the results of the extensive work of H. Staudinger, who received the Nobel Prize in Chemistry in 1953, finally became appreciated. Prior to Staudinger's work, polymers were believed to be colloidal aggregates of small molecules with quite nonspecific chemical structures.
- 29.1: Prelude
- The adoption of definite chemical structures for polymers has had far-reaching practical applications, because it has led to an understanding of how and why the physical and chemical properties of polymers change with the nature of the monomers from which they are synthesized. To a very considerable degree the properties of a polymer can be tailored to specific applications. Much of the emphasis in this chapter will be on how the properties of polymers can be related to their structures.
- 29.2: A Simple Addition Polymerization. The Parts of a Polymer
- The thermal polymerization of 1,3-cyclopentadiene by way of the Diels-Alder addition is not an important polymerization, but it does provide a simple concrete example of how a monomer and a polymer are related.
- 29.3: Types of Polymers
- Polymers can be classified in several different ways - according to their structures, the types of reactions by which they are prepared, their physical properties, or their technological uses.
- 29.4: Forces Between Polymer Chains
- Polymers are produced on an industrial scale primarily, although not exclusively, for use as structural materials. Their physical properties are particularly important in determining their usefulness, be it as rubber tires, sidings for buildings, or solid rocket fuels. Polymers that are not highly cross-linked have properties that depend greatly on the forces that act between the chains.
- 29.5: Correlation of Polymer Properties with Structure
- The properties of many of the commercially important thermoplastic and elastic polymers can be understood in terms of their chemical structures by using the concepts developed in the preceding section.
- 29.6: Condensation Polymers
- There is a wide variety of condensation reactions that, in principle, can be used to form high polymers. However, high polymers can be obtained only in high-yield reactions, and this limitation severely restricts the number of condensation reactions having any practical importance.
- 29.7: Addition Polymers
- We have discussed the synthesis and properties of a considerable number of addition polymers in this and previous chapters. Our primary concern here will be with some aspects of the mechanism of addition polymerization that influence the character of the polymer formed. The most important type of addition polymerization is that of alkenes (usually called vinyl monomers) such as ethene, propene, ethenylbenzene, and so on
- 29.8: Block, Graft, and Ladder Polymers
- A variation on the usual variety of copolymerization is the preparation of polymer chains made of rather long blocks of different kinds of monomers. A number of ingenious systems have been devised for making such polymers.
- 29.9: Naturally Occurring Polymers
- There are a number of naturally occurring polymeric substances that have a high degree of technical importance. Some of these, such as natural rubber, cellulose, and starch, have regular structures and can be regarded as being made up of single monomer units. Others, such as wool, silk and deoxyribonucleic acid are copolymers. We shall confine our attention here to wool and collagen, which have properties related to topics discussed previously in this chapter.
- 29.E: Polymers (Exercises)
- These are the homework exercises to accompany Chapter 29 of the Textmap for Basic Principles of Organic Chemistry (Roberts and Caserio).
Thumbnail: Polyethylene terephthalate polymer chain. (Public Domain; Jynto).
Contributors and Attributions
John D. Robert and Marjorie C. Caserio (1977) Basic Principles of Organic Chemistry, second edition. W. A. Benjamin, Inc. , Menlo Park, CA. ISBN 0-8053-8329-8. This content is copyrighted under the following conditions, "You are granted permission for individual, educational, research and non-commercial reproduction, distribution, display and performance of this work in any format."