1 - Introduction

Summary

Polymers and the scope of the book

Although many people probably do not realise it, everyone is familiar with polymers. They are all around us in everyday use, in rubber, in plastics, in resins and in adhesives and adhesive tapes, and their common structural feature is the presence of long covalently bonded chains of atoms. They are an extraordinarily versatile class of materials, with properties of a given type often having enormously different values for different polymers and even sometimes for the same polymer in different physical states, as later chapters will show. For example, the value of Young's modulus for a typical rubber when it is extended by only a few per cent may be as low as 10 MPa, whereas that for a fibre of a liquid-crystal polymer may be as high as 350 GPa, or 35 000 times higher. An even greater range of values is available for the electrical conductivity of polymers: the best insulating polymer may have a conductivity as low as 10⁻¹⁸ Ω⁻¹ m⁻¹, whereas a sample of polyacetylene doped with a few per cent of a suitable donor may have a conductivity of 10⁴ Ω⁻¹ m⁻¹, a factor of 10²² higher! It is the purpose of this book to describe and, when possible, to explain this wide diversity of properties.

The book is concerned primarily with synthetic polymers, i.e. materials produced by the chemical industry, rather than with biopolymers, which are polymers produced by living systems and are often used with little or no modification.