Dietrich Braun , Harald Cherdron , Matthias Rehahn , Helmut Ritter and Brigitte Voit Polymer Synthesis: Theory and Practice 5th ed. 2013 Fundamentals, Methods, Experiments 10.1007/978-3-642-28980-4_1 Springer-Verlag Berlin Heidelberg 2013
1. Introduction
The origin of polymer science as a part of organic chemistry goes back to the end of the nineteenth century when chemists detected that the properties of many substances with colloidal properties are connected with their molecular size. As a result of these and preferably of his own studies Hermann Staudinger (18811965) concluded in the early 1920s that substances like natural rubber, cellulose, and proteins but also many synthetic resins obtained by so-called polyreactions consist of large molecules, for which Staudinger proposed the term macromolecules. Nowadays, macromolecules and polymers are synonyms for substances with especially high molecular masses. However a sharp boundary cannot be drawn between low-molecular-weight and macromolecular substances; rather there is a gradual transition between them. One can say that macromolecules consist of a minimum of several hundred atoms. Accordingly, the lower limit for their molecular mass can be taken as around 103 g mol1.
Staudinger postulated that such macromolecules were built up from small so-called monomer units that were linked together by normal chemical binding forces and not by physical associations of small molecules. This hypothesis was by no means self-evident at that time and therefore became an object of many academic controversies between chemists and physicists until about the late 1930s. In the meantime Staudingers basic ideas of macromolecular chemistry are generally accepted.
In 1953 Staudinger received the Nobel prize in chemistry for his discoveries in the field of macromolecular chemistry. The scientific reputation of this new and rather young branch of chemistry is also confirmed by several other Nobel prizes, so to Paul J. Flory (in 1974) for his theoretical and experimental work in physical chemistry of macromolecules and to Karl Ziegler and Giulio Natta who in 1963 shared the Nobel prize for their discoveries in the field of chemistry and technology of polymers. More recently P.-G. de Gennes (1991, for discovering methods for order phenomena in liquid crystals and polymers); A.J. Heeger, A.G. MacDiarmid and H. Shirakawa (2000, for discovering and development of conducting polymers) and R.H. Grubbs, R.R. Schrock and Y. Chauvin (2005, catalyst development, e.g. for Ring Opening Metathesis Polymerization ROMP) were awarded.
Due to their high molecular masses, macromolecular substances (polymers) show particular properties not observed for any other class of materials. In many cases, the chemical nature, the size, and the structure of these giant molecules result in excellent mechanical and technical properties. They can display very long linear chains, but also cyclic, branched, crosslinked, hyperbranched, and dendritic architectures as well. The thermoplastic behaviour or the possibility of crosslinking of polymeric molecules allow for convenient processing into manifold commodity products as plastics, synthetic rubber, films, fibres, and paints (Fig. ).
Fig. 1.1
Macromolecular architectures
Man, however was by far not the first to recognize the tremendous potential of giant chain architectures: millions of years ago, nature developed macromolecules for many specific purposes. Cellulose, as example, is a substance which due to its extraordinary stress-stability-guarantees the shape and stability of the thinnest blade of grass and the largest tree even in a gust or strong storm.
Moreover, transformation of small molecules into high-molecular-weight materials changes solubility dramatically. Nature takes advantage of this effect for storage of energy by converting sugar into starch or glycogen, for example. Also, thin polymeric fibres and films are widely used in nature: spiders apply them to catch insects, silkworms to build their cocoons, crustaceans form their outer shell of it, birds their feathers, and mammals their fur. Last but not least, nature uses macromolecules to store the key information of life the genetic code by means of a polymer called DNA.
These few examples are ample evidence that nature benefitted from the advantages of long chain molecules for variety of central applications long before man discovered the use of polymer materials for similar purposes: for the longest time in our history we were unable to produce tailor-made macromolecules for protection, clothes and housing. Instead, we applied the polymeric material as it was provided by nature as wool, leather, cotton, wood or straw.
The first macromolecular substances which found technical interest were based on chemically modified natural materials, for example cellulose nitrate (Celluloid) or crosslinked casein (Galalith). Only with the onset of industrialisation in the nineteenth century did these renewable raw materials become the limiting factor for further growth, and chemists began developing artificial macromolecules based on fossil carbon sources like coal, oil, and gas. Polymers like condensation products from phenol and formaldehyde (Bakelite) started the plastics age in 1910 and polymers of styrene or vinyl chloride were used since about 1930 and until nowadays as important plastics. Presently, worldwide more than 260 million tons polymers per year are produced and used as plastics, films, fibres, and synthetic rubber.
More recently, so-called functional polymers with special physical or chemical properties have replaced other materials in many electrical or optical applications for microelectronic applications due to their electronic properties or have been used for biochemical purposes.
To sum up, macromolecular science covers a fascinating field of research and technology, focused on the creation, the understanding, and the tailoring of materials formed out of very high-molecular-weight molecules.
