Polymer Chemistry

Table of Contents

1. Frontmatter

2. 1. Introduction and Basic Concepts

   Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

   Abstract

   Among the many areas of chemistry, polymer science is a comparatively new field. The empirical use of materials made from natural substances with high molar masses has been documented for centuries; however, only the pioneering work of Hermann Staudinger in the 1920s (Staudinger 1920), a later Nobel laureate, provided the basis for a systematic understanding of this class of materials. In the decades since then, polymer science has developed to become both academically vivid and industrially extremely important. In particular, polymer science is characterized by its interdisciplinary nature. Indeed, polymer chemistry involves more aspects than perhaps any other branch of chemistry with other scientific disciplines:

3. 2. Polymers in Solution

   Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

   Abstract

   Polymers, especially when compared with the monomers from which they are built, have a number of special properties. For example, polymers such as starch and poly(propylene oxide) are much less soluble in water than their monomers, glucose and propylene oxide. Another observation is that many polymers absorb solvents or water without themselves dissolving. Thus, cotton socks, for instance, absorb water without disintegrating when they are washed in a washing machine. To explain and to be able to describe such properties, this chapter is devoted to a description of the polymeric chain structure and the consequences thereof for polymers in solution. Furthermore, the thermodynamics of polymer solutions are discussed and compared with those of small molecules to develop an understanding of the differences in solubility mentioned above.

4. 3. Polymer Analysis: Molar Mass Determination

   Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

   Abstract

   A key parameter for macromolecular substances is their molar mass or degree of polymerization. This chapter focuses on the question of how to mathematically describe and experimentally measure the molar mass of polymers and their molar mass distribution. A number of the methods presented have been developed exclusively for this purpose and are thus not commonly found in laboratories not concerned with polymer chemistry. In addition to the molar mass, it was discussed in ► Chap. 2 that the polymer size (e.g., of the entangled polymer coil in the melt or in solution) depends on the degree of polymerization. Therefore, some methods addressing this question are also presented.

5. 4. Polymers in Solid State

   Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

   Abstract

   The vast majority of all polymers produced in the world are utilized in their solid form—that is, as a classic material. Thus, a discussion of the solid-state properties of polymers, their morphology, and the impact of this and their properties on their applications is an essential part of this book.

6. 5. Partially Crystalline Polymers

   Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

   Abstract

   As a corollary to the basic introduction to polymers in their solid state, this chapter deals with partially crystalline polymers. To begin, we need to ask ourselves which polymers are able to crystallize.

7. 6. Amorphous Polymers

   Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

   Abstract

   The fundamental principles of “amorphous” polymers were introduced in ► Chap. 4. Some of their particular properties are described in more detail in this chapter.

8. 7. Polymers as Materials

   Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

   Abstract

   Polymers as materials appear in myriad forms. Everyone is familiar with floor coverings made of poly(vinyl chloride) (PVC) and with Plexiglas windows (poly(methyl methacrylate)), and the latter’s particularly successful version: the roof-top of the Munich Olympic Stadium. Many are equally familiar with the strengthening of polymers by compounding them with glass fiber. Polymers are also increasingly being used in medical applications, for instance, as bone and organ prostheses. One can easily imagine that these must meet completely different requirements than, for example, an ordinary PVC tube in a chemical laboratory. These few examples amply demonstrate how diversified and partially contradictory the requirements for a material in its specific application are, and that an ideal material for all applications cannot exist.

9. 8. Step-Growth Polymerization

   Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

   Abstract

   The synthetic processes of producing polymers from their monomers can be divided into step-growth and chain-growth polymerization. These two polymer formation reactions (◘ Figs. 8.1 and 8.2) are fundamentally different in their mechanisms, intermediate products, the way the molar mass increases as a function of monomer conversion, and the activation energy of their elementary steps.

10. 9. Radical Polymerization

    Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

    Abstract

    This chapter introduces the fundamental concepts of radical polymerization. Typical monomers, initiators, and transfer and termination reagents are discussed. Furthermore, the kinetic equations, the degree of polymerization, and molar mass distribution are derived.

11. 10. Ionic Polymerization

    Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

    Abstract

    Ionic polymerization, similar to radical polymerization, involves a chain mechanism in which either cations (cationic polymerization) or anions (anionic polymerization) are the active centers. Because the solution is electroneutral, the number of active centers and their counterions is identical. Whether a monomer with a carbon-carbon double bond can be polymerized anionically or cationically depends on the electron density of the double bond, which in turn depends on the substituents. If the substituents induce a donor effect (OR, NR₂, C₆H₄–CH₃), then the monomer favors a cationic polymerization. By contrast, monomers with acceptor substituents (CN, COOR, CONR₂) can be anionically polymerized. Because the growing chains are identically charged, they cannot terminate the reaction by, for example, combining with one another which means they remain active. A complete lack of termination reactions is known as a living polymerization (cf. Cap. ► 10.2.6). The chains can be extended by the addition of more monomers. Block copolymers can be synthesized by adding other monomers capable of polymerization. Additionally, the molar masses can be controlled using the ratio [M]:[I].

12. 11. Coordination Polymerization

    Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

    Abstract

    Nearly half of all polymers produced worldwide (according to production volume) are produced by catalytic polymerization reactions carried out in the presence of transition metal compounds. Especially polypropene and a large proportion of polyethene are produced in this way. This chapter deals with the fundamental principles of this industrially enormously important but also academically interesting and multifaceted field of chemistry. Since the coordination of the monomer on a metal atom plays an important role in the catalytic cycle, this polymerization technology is also known as coordination polymerization.

13. 12. Ring-Opening Polymerization

    Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

    Abstract

    Ring-opening polymerization (ROP) is an important method of polymerization. It differs from radical polymerization (► Chap. 9), ionic polymerization (► Chap. 10), and step-growth polymerization (► Chap. 8). No low-molar-mass by-products are formed, except during the polymerization of Leuchs’ anhydride (◘ Figs. 12.41 and 12.42). Furthermore, the driving force derived from the transformation of C=C double bonds into C–C single bonds, which offsets the loss of entropy during polymerization, is not available. A general feature of ROP is that the monomers are rings of varying size. Depending on the size and type of the ring structure, the ability to polymerize and the corresponding driving force varies. Small rings (three-, four-, or five-membered rings) can be polymerized because of the ring strain released when they open. As an example, the enthalpy associated with the ring strain of oxirane is 116 kJ/mol. The release of enthalpy is also the driving force for the polymerization of seven- and eight-membered lactones and lactams even though the ring strain is only about 16 kJ/mol for these monomers. Unstrained six-membered rings often do not polymerize via ROP. By contrast, the ROP of disulfides, silicones, and carbonates can be ascribed to the increase in the entropy that occurs during the polymerization of these monomers. This increase in entropy is based on the increase in the degrees of freedom of rotation gained when rings are transformed into open chains.

14. 13. Copolymerization

    Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

    Abstract

    If two different monomers, M₁ and M₂, are polymerized together, the structures shown in ◘ Fig. 13.1 can result.

15. 14. Important Polymers Produced by Chain-Growth Polymerization

    Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

    Abstract

    The technically most important polymers and copolymers produced by chain-growth polymerization are discussed in this chapter; those produced via step-growth polymerization are discussed in ► Sect. 8.5. The global market for polyolefins (including polyethene, polypropene, and diverse copolymers) is estimated at 160 million tons (2018). The global market for synthetic elastomers (almost all synthetic elastomers are produced via chain-growth polymerization.) in 2020 was ca. 14.2 million tons.

16. 15. Chemistry with Polymers

    Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

    Abstract

    Many macromolecules still contain chemically reactive groups even after polymerization has taken place. Therefore, such 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.

17. 16. Industrially Relevant Polymerization Processes

    Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

    Abstract

    In this chapter, industrially relevant polymerization methods are described in more detail. The focus is on chain-growth polymerization, and special attention is paid to the heterogeneous methods—suspension and emulsion polymerization. Gas phase polymerization is dealt with separately in ► Sect. 11.5.

18. 17. The Basics of Plastics Processing

    Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

    Abstract

    With the exception of the functional polymers discussed in ► Chap. 19, polymers are typically used as solid materials for the widest variety of different objects, from plastic bags to prostheses. To fulfill each requirement, one needs to take the material, composed of macromolecules that have been produced in solution, bulk, or dispersion, and give it form and precise geometry depending on the demands of the intended application. The exact conditions of normal use to which the object is exposed to determine the choice of the chemistry of the material, for example, thermal, mechanical, and chemical properties; the actual use determines the geometry of the article. Many different processing technologies for shaping polymeric materials have been developed over the past few decades. However, all forms cannot be achieved with all processes, and all polymers cannot be processed using all techniques. This is why it is exceptionally important for a polymer chemist to have at least some fundamental knowledge of the interplay between shape, material, and processing technique. This chapter provides a short, introductory overview of the most important aspects and the basic concepts of polymer processing. For further details that are beyond the scope of this book, the interested reader is referred to more comprehensive textbooks (Kaiser 2007; Michaeli 2010).

19. 18. Elastomers

    Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

    Abstract

    Characteristic of elastomers is that they have a glass temperature below ambient temperature; however, in contrast to thermoplastics, the most obvious property of cross-linked elastomers is their almost completely reversible elastic behavior. Some cross-linked elastomers can be stretched to up to seven times their original length and still return almost immediately to their original length. On account of this, this chapter is dedicated to this class of materials.

20. 19. Functional Polymers

    Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

    Abstract

    Classical polymer materials such as polyethylene and polyamide are familiar to all of us because of the multiplicity of uses in everyday life. Equally as omnipresent, but less well known, are the so-called functional polymers. As opposed to the structures previously discussed in ► Chaps. 3–7, these polymers do not belong to the group of solid materials (“plastics”). Instead, these materials are mostly used in solution, where they induce a certain physical effect. Thus, most frequently it is not the polymer itself that is recognized but rather its effect or function—hence the name functional polymers. They are also referred to as polymeric agents or polymeric active ingredients (Göthlich et al. 2005). Despite being so inconspicuous, many areas of our daily lives would be very different without them. For example, they are used in detergents, pharmaceuticals, and cosmetics.

21. 20. Liquid Crystalline Polymers

    Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

    Abstract

    In this chapter, liquid crystals are defined, methods for their characterization are described, and some examples of liquid crystalline polymers are discussed.

22. 21. Polymers and the Environment

    Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

    Abstract

    Around 348,000,000 (348 million!) tons of synthetic polymers were produced in 2018. The main producer is China. A further annual increase of 4–5% is expected for the next years. In light of these numbers, one must question the impact this consumption and use have on the environment. This concerns not only the resulting high volumes of waste produced but also issues such as recycling, energy, renewable raw materials, and sustainability. Close relationships and interactions exist between all these fields, which should not be ignored but are, nevertheless, all too often insufficiently considered in current discussions of these questions.

23. 22. Selected Developments in Polymer Science

    Sebastian Koltzenburg, Michael Maskos, Oskar Nuyken

    Abstract

    This chapter discusses a few selected developments that have caught our attention in recent years for a variety of reasons. This selection is subjective. One or the other topic may remain in the realm of laboratory curiosities in the medium term; these examples are interesting primarily because of their originality.

24. Backmatter