Chemistry with Polymers
Many macromolecules still contain chemically reactive groups even after polymerization has taken place; under certain conditions, macromolecules can also be reactive chemicals. They do, however, have some special characteristics compared with reagents wit
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Chemistry with Polymers 15.1 Polymer Analogous Reactions – 408 15.1.1 Special Kinetic Features of Polymer Analogous Reactions – 409 15.1.2 Intra- Vs. Intermolecular Reactions – 410 15.1.3 Technically Significant Polymer Analogous Reactions – 411
15.2 Cross-Linking Reactions – 413 15.2.1 Cross-Linking of Polyolefins – 413 15.2.2 Vulcanization of Rubber – 413 15.2.3 Photoresists – 414 15.2.4 Paints – 415 15.2.5 Thermoreversible Cross-Linking: Ionomers – 418
15.3 Degradation Processes in Polymeric Materials – 418 15.3.1 Degradation Mechanisms – 420 15.3.2 Stabilization of Polymers – 421
References – 424
© Springer-Verlag Berlin Heidelberg 2017 S. Koltzenburg et al., Polymer Chemistry, DOI 10.1007/978-3-662-49279-6_15
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Chapter 15 · Chemistry with Polymers
Many macromolecules still contain chemically reactive groups even after polymerization has taken place; under certain conditions, macromolecules can also be reactive chemicals. They do, however, have some special characteristics compared with reagents with a low molar mass. This chapter describes such reactive macromolecules and their peculiarities. It is of fundamental importance to differentiate between two types of chemical reactions that macromolecules can undergo: intentional chemical reactions or undesired degradation processes. Specific stabilization strategies have been developed to inhibit unwanted degradation processes, and these are also dealt with in this chapter. 15.1
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Polymer Analogous Reactions
Reactions that involve parts of macromolecules, but that do not change their degree of polymerization, are known as polymer analogous reactions. The hydrogenation of unsaturated bonds in the polymer backbone or the hydrolysis of side groups are examples of these kinds of reactions. Because the molar mass of the repeat unit usually changes during these reactions, the molar mass of the macromolecule does not remain constant (in contrast to the degree of polymerization). From a synthetic polymer chemist’s point of view, polymer analogous reactions are fundamentally different to reactions involving only small molecules in several ways: 55 By-products are difficult to separate from the desired products so that only reactions that do not generate significant amounts of unwanted by-products are suitable for polymer analogous reactions. 55 The solubility of a chemically modified polymer can be very different from that of the base polymer. This is especially pronounced if charged moieties are added to an uncharged polymer, for example, the hydrolysis of ester to carboxylate groups. This can make polymer analogue reactions difficult as, because of its reduced solubility, the polymer precipitates during the reaction, resulting in the unconverted functional groups no longer being easily available for reaction; the reaction does not go to completion and a chemically inhomogeneous product is formed. Chemically inhomogeneous products are also obtained if a poorly soluble polymer (e.g., cellulose) is made more soluble by modification. Nevertheles
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