Copolymers terminology

Table 2.7 defines a number of terms used in block copolymer terminology, as well as other structures described later (20). These structures are also illustrated in Figure 2.10 (20). 

When Fj = 1/f2, the copolymer composition curve will be either convex or concave when viewed from the Fj axis, depending on whether Fj is greater or less than unity. The further removed from unity rj is, the farther the composition curve will be displaced from the 45° line. This situation is called ideal copolymerization. The example below explores the origin of this terminology. 

For the statistical copolymer the distribution may follow different statistical laws, for example, Bemoullian (zero-order Markov), first- or second-order Markov, depending on the specific reactants and the method of synthesis. This is discussed further in Secs. 6-2 and 6-5. Many statistical copolymers are produced via Bemoullian processes wherein the various groups are randomly distributed along the copolymer chain such copolymers are random copolymers. The terminology used in this book is that recommended by IUPAC [Ring et al., 1985]. However, most literature references use the term random copolymer independent of the type of statistical distribution (which seldom is known). 

Distillation terminology is also borrowed for instances when the copolymer composition is the same as that of the comonomer feed from which it is derived. Such a feed composition is called an azeotrope by analogy with distillation. Under these conditions r/[MI ]/[Pg.249]

Addition of monomer to backbone radical. The addition of the monomer to the backbone radical R- may be considered as equivalent to the copolymerization of M2 with the radical from monomer Mj. Thus, in the terminology of the copolymerization equation the reaction rate coefficient of importance is ki2 and the estimates of the magnitude of this place it sufficiently high to ensure that the monomer will add to the mdical site in polyethylene (Russell, 2002). The monomer will add preferentially to tertiary sites over secondary sites in ethylene copolymers with a high concentration of propylene, but in LDPE there seems to be little preference for branch points. 

Figure 7.2 shows curves for several nonideal cases, that is, where r T2 1. It is seen that when both r and T2 are less than 1 there exists some point on the i i-versus-/i curve where the copolymer composition equals the feed composition and at this point the curve crosses the line F = f (that is, the diagonal line). At this point of intersection, polymerization proceeds without change in either feed or copolymer composition. Distillation terminology is again borrowed for this instance. Azeotropic copolymerization is said to occur at such points and the resulting copolymers are called azeotropic copolymers. 

The thermoplastic IPNs utihze physical cross-hnks, rather than chemical crosshnks. Usually, these materials wiU flow when heated to sufficiently high temperature (hence the terminology thermoplastic), but behave as thermosets at ambient temperature, with IPN properties, often possessing dual phase continuity. Most often, physical crosshnks are based on triblock copolymers (thermoplastic elastomers being the leading material), ionomers, or semi-crystalhne materials. 

When it became apparent that the lysosomal thiol-proteinases were particularly important in the degradation of HPMA copolymer side-chains, a new series of side-chains was designed to meet known specificities of particular lysosomal enzymes.29 Two side-chains were synthesized (-Gly-Phe-Leu-Gly-Phe-NAp and -Gly-Gly-Phe-Leu-Gly-Phe-NAp) which contain a pentapeptide sequence previously shown O to be susceptible to the lysosomal proteinase cathepsin D, a thiol-independent enzyme. Five further sequences were prepared containing hydrophobic amino acids in the P2 and P positions in relation to the terminal bond (according to the terminology of... 

The terminology used to describe acrylamide-containing polymers in the technical literature varies in its precision. In order to avoid confusion, throughout this article the term poly(acrylamide) is reserved for the nonionic homopolymer of acrylamide, whereas the term polyacrylamides or acrylamide polymers refers to acrylamide-containing polymers, including the homopolymer and copolymers. Specific nomenclature is used for particular copolymers, for example, poly(acrylamide-co-sodium acrylate). 

Wool and silk are both proteins. AU proteins are actually copolymers of polyamide-2 (or nylon-2, old terminology). As made by plants and animals, however, the copolymers are highly ordered, and they have monodisperse molecular weights, meaning that aU the chains have the same molecular weights. 

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