Polymer properties, reference text

The purpose of this section is not only to confirm the identification, but also to characterize certain polymers and polymer types in detail. Although methods to determine microstructures and impurities, such as chemical inversions, modifications, and multiple bond formations, are different from polymer to polymer and are discussed separately, the methods used for the determination of density and crystallinity, as well as polymer orientation, are common to most polymers. Thus, the determination of crystallinity and density will be covered in this section, in Sec. 3.1, and likewise, the orientation of the polymer chain will be described in Sec. 3.2. The use of absorption coefficients to calculate properties, such as crystallinity, doublebond content, chain branching, and monomer ratios, is described in reference texts [14,15]. Today most work is performed by Fourier transform infrared (FTIR), and so an attempt has been made to feature coefficients from the latest reference sources, which include data acquired by FTIR. 

While several preparative routes may exist for the synthesis of a given heterocyclic polymer, we have attempted to portray the method that has received the most common usage. Throughout our discussion we have attempted to reference and supplement the most recent and definitive texts, monographs and reviews that exist on a given subject. In addition, whenever possible we have indicated what particular properties and attending applications are accrued by inclusion of the heterocycle in the polymer framework. 

The mechanical properties of polymer chains that do not exhibit interactions between the side chains and the backbone, or one part of the backbone and another part of the backbone, are related to the number of available conformations and hence the chain entropy. As we discuss later, the stiffness of a polymer chain that does not exhibit bonding with other parts of the chain is related to the change in the number of available conformations. It turns out this refers to random chain polymers of which elastin, poly(ethylene) at high temperatures, and natural rubber are discussed in this text. As we stretch a polymeric chain we reduce the number... 

As in previous chapters, the presentation remains restricted to kinetic principles and their applications in modeling. No attempt is made to review the intricacies of reactivities of monomers and their molecular causes or their effect on polymer structure and properties. For details of these, the reader is referred to excellent texts on the subject [G1-G12],... 

Within this chapter we describe the principles of three of the most important techniques employed to unravel the interfacial properties of polymers. It is not our intention to provide an exhaustive theoretical and historical perspective on the methods described and only an overview will be given, interested readers should refer to some of the excellent texts which are cited in each section if they wish a more thorough grasp of these techniques. 

The major objective of this text is to provide information on the basic microscopy techniques and specimen preparation methods applicable to polymers. This book will attempt to provide enough detail so that the methods described can be applied, and will also reference appropriate publications for the investigator interested in more detail. Some discussion will consider polymer structure and properties, but only as this is needed to put the microscopy into context. 

Various introductory texts in this field have been prepared for conservators in the past decades (Torraca, 1968 Feller etal., 1971 Conservation Unit, 1992). Many more books are now available for schools and the general public that outline the concepts and properties of polymers. More detailed reference books that assume some knowledge of chemistry include Painter and Coleman (1997), Brydson (1999), and Cowie and Arrighi (2008). The reader is assumed to have access to publications of the International Institute for Conservation. Polymers that have been adequately described in those publications have been given a slighter treatment here to avoid duplication. 

The separation of electrical behaviour into dielectric and bulk conductive properties is convenient and has been followed in this review. There has been some selection in the material covered. In part this reflects the authors interest, but it is also a consequence of the amount known about the electrical properties of polymers. Coverage of this now large fidd would require several volumes, and in fact a number of excellent texts and review articles are available which deal with sheets of the field. The reader is referred to some of these in the appropriate parts of this review. 

Unlike the case for metals, secondary bonds are of great importance in polymers. These bonds are much weaker than covalent bonds, but for even moderate chain length polymers these bonds have a significant impact on the molecular and bulk properties of these materials. These intermolecular bonds are based on electrostatic interactions and are due to either attractions between permanent dipoles, quadmpoles, and other multipoles, or between a permanent multipole and an induced charge on a second molecule (or moiety, in the case of a polymer), or between transient multipoles. All such secondary bonds can be considered van der Waals forces, but many texts use van der Waals to denote induced and/or transient multipole interactions only. The induced interaction is sometimes referred to as polarization, or sometimes induction bonding. The transient interaction is very weak and is known as dispersion or London dispersion forces, and arises from electrostatic interactions between two molecules due to temporary inhomogeneous electron density distributions in the outermost electron shells of these molecules. 

The molecular chain architecture of a polymer also imparts many unique attributes, including temperature and rate dependence. Some of these unique properties are further illustrated in the specific case of UHMWPE in subsequent sections of this chapter. For further background on general polymer concepts, the reader is referred to texts by Rodriguez [1] and Young [2]. 

Binary mixtures of a flexible polymer and a rigid rod-like molecule (nematogen or liquid crystal) play an important role in electro-optical devices, such as light shutters and displays. Since the miscibility or phase separation controls the performance of the materials, the phase behavior and phase separation kinetics have been of fundamental and practical interests. Liquid crystalline domains dispersed in a polymer matrix are called polymer dispersed-liquid crystals (PDLCs), or polymer-stabilized liquid crystals (PSLCs), where the polymer forces the liquid crystals to phase separate into droplets surrounding by the polymer matrix [2]. Practically, there are many ways to create PD LCs by mixing polymers and liquid crystals the emulsion method [37] and phase separation method [38], including polymerization-, thermally-, and solvent-induced phase separations. The reader is referred to text books [1, 2] for details of PDLC and a review [39] for the rheological and mechanical properties. 

The refractive indices of polymers provide fundamental physical property information that can be used in characterization, processing, and usage analyses. In-depth description of refractive indices based on classic electromagnetic theory can be found in basic texts (1,2). The purpose of this monograph is to provide a convenient reference of values and some general remarks in approximating and utilizing refractive indices of polymers. 

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