Polymer, classification functionization

FIG. 13.13 The dynamic shear moduli, G and G", for a high molecular weight polymer, as functions of the angular frequency. Classification is also indicated. Analogous to Ferry (1970) and Te Nijenhuis (1980, 2006). 

Similarly to small molecules, polymers can be classified based on their chemical nature, i.e. based on the functional groups present in their molecule. However, different from small molecules, one important element in polymer classification is the chemical structure of the polymeric backbone. The attached side atoms or groups of atoms to the polymer backbone play a different role compared to that of the presence of various atom types or groups of atoms in the backbone. For example, it is a significant difference between poly(oxy-1,4-phenylene-oxy-ethylene) that contains phenyl groups and oxygen atoms in the polymer backbone and poly(phenyl vinyl ether) that is a vinyl type polymer with a carbon chain as backbone, although both polymers are ethers. The two polymers are synthesized differently and have quite different properties. Their structures are shown below ... 

Classification of polymers by functional type is not generally suitable because some of the classes would be excessively large and the reader might have to search several classes to find a particular compound. Indexing by formula requires too much time and effort in searching for common polymers. The best solution is a simple alphabetical listing. To make an alphabetical listing practical it is necessary to define a set of rules of nomenclature. 

There is an extremely wide range of potentially useful chemical treatments available, and for any boiler system, proper selection, utilization, and control are vital considerations that may largely determine the ultimate success of the overall program. These chemicals usually are organized by type of compound, function, mode of action, or similar classification, but, because many chemicals are multifunctional in character, may be used in either a primary or supplementary (adjunct or conjunctional treatment) role, and additionally may be branded (especially many modem polymers) or otherwise disguised, such classifications may be quite arbitrary. 

Beyond N=9, y, (C) becomes higher than y (A). In general, the relative classification of the studied polymers hyperpolarizabilities does not follow the increase in the number of K electrons. An explanation can be found, if we consider the two important factors which are the lengthening of the polymeric chain and bond alternation. In Table 7, are given the MNDO optimized lengths L, of the studied oligomers. The variation of L as a function of N, is plotted in Figure 6. We can see that for any N value, we have approximately the classification ... 

The A-B type iniferters are more useful than the B-B type for the more efficient synthesis of polymers with controlled structure The functionality of the iniferters can be controlled by changing the number of the A-B bond introduced into an iniferter molecule, for example, B-A-B as the bifunctional iniferter. Detailed classification and application of the iniferters having DC groups are summarized in Table 1. In Eqs. (9)—(11), 6 and 7 serve as the monofunctional iniferters, 9 and 10 as the monofunctional polymeric iniferters, and 8 and 11 as the bifunctional iniferters. Tetrafunctional and polyfunctional iniferters and gel-iniferters are used for the synthesis of star polymers, graft copolymers, and multiblock copolymers, respectively (see Sect. 5). When a polymer implying DC moieties in the main chain is used, a multifunctional polymeric iniferter can be prepared (Eqs. 15 and 16), which is further applied to the synthesis of multiblock copolymers. 

To avoid the obviously incorrect classification of polyurethanes as well as of some other polymers as addition polymers, polymers have also been classified from a consideration of the chemical structure of the groups present in the polymer chains. Condensation polymers have been defined as those polymers whose repeating units are joined together by functional... 

It should not be taken for granted that all polymers that are defined as condensation polymers by Carothers classification will also be so defined by a consideration of the polymer chain structure. Some condensation polymers do not contain functional groups such as ester or amide in the polymer chain. An example is the phenol-formaldehyde polymers produced by the reaction of phenol (or substituted phenols) with formaldehyde... 

In this section, enzymes in the EC 2.4. class are presented that catalyze valuable and interesting reactions in the field of polymer chemistry. The Enzyme Commission (EC) classification scheme organizes enzymes according to their biochemical function in living systems. Enzymes can, however, also catalyze the reverse reaction, which is very often used in biocatalytic synthesis. Therefore, newer classification systems were developed based on the three-dimensional structure and function of the enzyme, the property of the enzyme, the biotransformation the enzyme catalyzes etc. [88-93]. The Carbohydrate-Active enZYmes Database (CAZy), which is currently the best database/classification system for carbohydrate-active enzymes uses an amino-acid-sequence-based classification and would classify some of the enzymes presented in the following as hydrolases rather than transferases (e.g. branching enzyme, sucrases, and amylomaltase) [91]. Nevertheless, we present these enzymes here because they are transferases according to the EC classification. 

Classification by End Use Chemical reactors are typically used for the synthesis of chemical intermediates for a variety of specialty (e.g., agricultural, pharmaceutical) or commodity (e.g., raw materials for polymers) applications. Polymerization reactors convert raw materials to polymers having a specific molecular weight and functionality. The difference between polymerization and chemical reactors is artificially based on the size of the molecule produced. Bioreactors utilize (often genetically manipulated) organisms to catalyze biotransformations either aerobically (in the presence of air) or anaerobically (without air present). Electrochemical reactors use electricity to drive desired reactions. Examples include synthesis of Na metal from NaCl and Al from bauxite ore. A variety of reactor types are employed for specialty materials synthesis applications (e.g., electronic, defense, and other). 

Let s start by developing an overview of the major types of polymers. We can categorize polymers in a number of ways. We will develop chemical as well as structural classifications later in the text when we learn about their synthesis and properties. However to begin, we will divide them on the basis of origin and function. We have already alluded to two different types natural and synthetic. Table 1-1 lists several types of natural polymers and provides examples of each. As their name implies, natural polymers occur in nature. 

The less ambiguous classification is based on the polymerization mechanism, which can be either chain growth or step (nonchain) growth. In the latter case, a given functional group has similar if not identical reactivity, whether it is in the monomer or at the polymer chain end. In a chain growth mechanism, only monomer adds to the active species at the growing chain end i.e., two monomer molecules will not react with each other. 

Hole transport in polymers occurs by charge transfer between adjacent donor functionalities. The functionalities can be associated with a dopant molecule, pendant groups of a polymer, or the polymer main chain. Most literature references are of doped polymers. The more common donor molecules include various arylalkane, arylamine, enamine, hydrazone, oxadiazole, oxazole, and pyrazoline derivatives. Commonly used polymers are polycarbonates, polyesters, and poly(styrene)s. Transport processes in these materials are unipolar. The mobilities are very low, strongly field and temperature dependent, as well as dependent on the dopant molecule, dopant concentration, and the polymer host This chapter reviews hole transport in polymers and doped polymers of potential relevance to xerography. The organization is by chemical classification. The discussion mainly includes molecularly doped, pendant, and... 

Physically persistent stabilizers classified as functionalized oligomers or polymers can be synthesized by polyreactions of functionalized monomers and/or by polymer analogous reactions exploiting the reactivity of functionalized reactive low molecular weight compounds with polymeric substrates. For a detailed classification of synthetical approaches, the classification principle used in Houben-Weyl [42] was adopted. The nomenclature of functionalized polymers is based on the monomer s unit principle. Abbreviations of conventional polymers are used as recommended by [1, 2]. 

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