Methods and Techniques for Synthesis, Characterization, Processing, and Modification of Polymers

Abstract

In this chapter, the fundamentals and the most common methods and techniques for the synthesis, processing, characterization, and modification of mac-romolecular materials are described briefly, as an introduction to the special Chaps. 3,4, and 5. The main emphasis is on the description of methods and techniques used in laboratories, but some examples from industrial practice are also mentioned. 2.1 Methods for Synthesis of Polymers The formation of synthetic polymers is a process which occurs via chemical connection of many hundreds up to many thousands of monomer molecules. As a result, macromolecular chains are formed. They are, in general, linear, but can be branched, hyperbranched, or crosslinked as well. However, depending on the number of different monomers and how they are connected, homo-or one of the various kinds of copolymers can result. The chemical process of chain formation may be subdivided roughly into two classes, depending on whether it proceeds as a chain-growth or as a step-growth reaction. 2.1.1 Chain Growth Polymerizations Chain growth polymerizations (also called addition polymerizations) are characterized by the occurrence of activated species (initiators)/active centers. They add one monomer molecule after the other in a way that at the terminus of each new species formed by a monomer addition step an activated center is created which again is able to add the next monomer molecule. Such species are formed from compounds which create radicals via homolytic bond scission, from metal complexes, or from ionic (or at least highly polarized) molecules in the initiating steps (2.1) and (2.2). From there the chain growth can start as a cascade reaction (propagation; 2.3) upon manifold repetition of the monomer addition and rees-tablishment of the active center at the end of the respective new product: