Polymer Families

Within the scope of the original definition, a very wide variety of ionomers can be obtained by the introduction of acidic groups at molar concentrations below 10% into the important addition polymer families, followed by partial neutralization with metal cations or amines. Extensive studies have been reported, and useful reviews of the polymers have appeared (3—8). Despite the broad scope of the field and the unusual property combinations obtainable, commercial exploitation has been confined mainly to the original family based on ethylene copolymers. The reasons for this situation have been discussed (9). Within certain industries, such as flexible packaging, the word ionomer is understood to mean a copolymer of ethylene with methacrylic or acryhc acid, partly neutralized with sodium or zinc. 

Conventional rubbers are members of the polymer family in that they consist of long chain-like molecules. These chains are coiled and twisted in a random... 

The general approaches for the synthesis of poly(arylene ether)s include electrophilic aromatic substitution, nucleophilic aromatic substitution, and metal-catalyzed coupling reactions. Poly(arylene ether sulfone)s and poly(arylene ether ketone)s have quite similar structures and properties, and the synthesis approaches are quite similar in many respects. However, most of the poly(arylene ether sul-fone)s are amorphous while some of the poly(arylene ether)s are semicrystalline, which requires different reaction conditions and approaches to the synthesis of these two polymer families in many cases. In the following sections, the methods for the synthesis of these two families will be reviewed. 

Figure 5. Liquid crystalline polymer family of this study.

Polyarylenevinylene (PAV) expressed by the chemical formula of [-Ar-CH=CH-]n, where Ar is an arylene ring, is an attractive n-conjugated polymer family because of the following features (i) by the thermal conversion from polyelectrolyte or organic-solvent-soluble precursors, one can obtain the PAV films which have large third-order susceptibility and excellent optical quality, and (ii) the band gap can be adjusted by suitable selection of the arylene rings. 

Written by foremost experts in the field from industry and academia, these books place particular emphasis on structure-property relationships of polymers and manufacturing technologies as well as their practical and novel applications. The aim of each book in the series is to provide readers with an in-depth treatment of the state-of-the-art in that field of polymer technology. Collectively, the series will provide a definitive library of the latest advances in the major polymer families as well as significant new fields of development in polymer science. 

Table 2.32 displays the share of the wire cable sector in the total consumption of each polymer family. 

Table 2.33 Share of the electrical electronics sector, excluding vrires cables, in the total consumption of certain polymer families...

Once the specification is established, a first pre-selection of the materials having the required minimal properties can be made using the following graphs (see Figures 3.11 to 3.38). For the selected polymer families, one should then refer to the corresponding monographs to determine those that satisfy all the points of the specifications. 

Thermoplastic families are diverse but their number is limited and often there are wide gaps between the properties of two basic polymer types. To bridge the gap, two polymer families can be mixed if they are compatible or if it is possible to compatibilize them with a third material. 

Choosing a reinforced plastic or one from a more-sophisticated polymer family to provide higher performance can be used to cut overall costs by reducing wall thickness and thus reducing material weight and material cost and enhancing the processing. 

Launching new polymers of medium-range performance is a difficult operation economically, as proved by the case of the aliphatic polyketones. New polymer families are rarely marketed but there are some examples where they provide improved processing performances, which is a particularly needed property to satisfy economic requirements. Modification of existing polymers is also an interesting route. Let us quote some examples ... 

Chemolysis certain polymer families such as polyurethane are chemically depolymer-ized. This is theoretically the best recycling solution if the performances of the original material are to be recovered and if the recyclate is used in the same application. This is, technically and economically, a difficult method that is industrialized in few cases. 

Blending of the lowest price commodity polymers from synthetic and carbohydrate polymer families [e.g., poly(ethylene) and starch] would appear to follow these laws. Although each polymer class is produced in large volume (first law), the production rate for com starch/synthetic polymer blends is much lower than that for the synthetic polymer this slower extrusion rate directly affects the final cost. Ignoring this limitation, the film properties of the blend are significantly poorer than those of the synthetic polymer film. Both deficiencies are related to the poor thermoplastic properties of water-soluble polymers such as cora-starch. 

Dow Chemical has launched a range of foams which are said to exceed industry standards for softness and toughness. This article supplies brief details of the foams which are based on Dow s Insite catalyst technology. Synergy Soft Touch Foams are produced using Dow s Index Interpolymers, a new thermoplastic polymer family based on the copolymerisation of ethylene and styrene. The foams are offered in three grades of softness, and other properties include shock absorption, vibration damping and insulation. 

Many polymer families are referred to by the name of the particular linkage that connects the polymers (Table 2). The family name is poly followed by the linkage name. Thus, those polymers that contain an ester linkage are known as polyesters those with an ether linkage are called polyethers, etc. 

Poly(esters) (Table 11.2) are the first class of polymers discussed, as they are the most widely investigated of all of the polymer families for oral protein delivery. Poly(esters) used for oral drug delivery have primarily been biodegradable polymers (Figure 11.1). Biodegradation is the primary delivery mechanism for poly(ester) polymers used for protein and peptide delivery. The degradation properties of poly(esters) are dependent on the monomers used to produce the poly(ester). Several poly(esters) are discussed in detail in the following sections. 

The second synthetic route to PAE containing quinoxaline units involved the reaction of an aromatic dihydroxy quinoxaline or aromatic bis(hydroxy-quinoxaline) with activated aromatic difluoro compounds (Eq. (3)) [15]. The dihydroxy quinoxaline and bis(hydroxyquinoxaline) monomers were readily prepared from the condensation of 1,2-diaminobenzene with 4,4 -dihydroxyben-zil and aromatic bis(o-diamines) with 4-hydroxybenzil, respectively. The Tgs of a series of PAE containing quinoxaline units are presented in Tables 3 and 4. For these polymers, the trend for the Tg is sulfone > carbonyl > terephthaloyl-> isophthaloyl. This trend holds for most polymer families when polymers of similar molecular weights are compared. Several polyphenylquinoxalines of the same chemical structure as those in Table 3 were also prepared by the poly-... 

Amorphous polymers characteristically possess excellent optical properties. Unlike all the other commercially available fluoropolymers, which are semicrystalline, Teflon AF is quite clear and has optical transmission greater than 90% throughout most of the UV, visible, and near-IR spectrum. A spectrum of a 2.77-mm-thick slab of AF-1600 is shown in Figure 2.5. Note the absence of any absorption peak. Thin films of Teflon AF have UV transmission greater Ilian 95% at 200 mm and are unaffected by radiation from UV lasers. The refractive indexes of Teflon AF copolymers are shown in Figure 2.6 and decrease with increasing FDD content. These are the lowest refractive indexes of any polymer family. It should be noted that the abscissa could also be labeled as glass transition temperature, Tg, since Tg is a function of the FDD content of the AF copolymer. Abbe numbers are low 92 and 113 for AF-1600 and AF-2400. 

Three families of polymers have been used to study transfection mechanisms polyamines, polyamides, and polyvinyl type polymers. The transfection efficiencies achievable with these systems vary widely, so an in-depth analysis of each polymer family and subsequent comparison of what affects gene delivery will be discussed in this chapter. In addition to high transfection efficiency, it is important for the polymeric systems to be relatively nontoxic to cells in vitro and not to elicit an immune response in vivo. Thus, the effect of transfection parameters on cytotoxicity and immunogenicity will also be examined. 

As a silicone mbber membrane is not permeable to hydrophilic or high molecular weight compounds, concerted efforts were made to develop other biocompatible polymers for use in implantable devices. Such polymers include poly(ethylene-co-vinyl acetate), poly (ethylene), poly(propylene), poly(hydroxymethyl methacrylate), poly(lactide-co-glycolide), poly (anhydrides) and poly(ortho esters). The characteristics and applications of each important polymer family will be discussed later in this chapter. 

Tables 2.2 and 2.3 give a survey of the principal polymer families belonging to these two classes.

Main polymer families (often obtained by ring-opening polymerisation)... 

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