2-/- , Staudinger

Some exceptionally gifted researchers have made contributions to the topics we discuss here, and their impact on these and other areas of inquiry have earned them special recognition. Specifically, we note that Einstein,. Svedberg, Staudinger, and Flory have all been awarded the Nobel Prize, and Stokes and Poiseuille have been honored by having units named after them. These are but a few of the superstars whose work we encounter in this chapter. 

This relationship with a = 1 was first proposed by Staudinger, but in this more general form it is known as the Mark-Houwink equation. The constants k and a are called the Mark-Houwink coefficients for a system. The numerical values of these constants depend on both the nature of the polymer and the nature of the solvent, as well as the temperature. Extensive tabulations of k and a are available Table 9.2 shows a few examples. Note that the units of k are the same as those of [r ], and hence literature values of k can show the same diversity of units as C2, the polymer concentration. 

H. Staudinger, Die Hochmolekularen organische Uerbindungen Kautschuk und Cellolose Springer-Vedag, Berlin, 1932. 

The first synthetic route for isocyanates was reported in 1848 (10,11)- Subsequent efforts by Hofmann, Curtius, and Hentschel pioneered alternative synthetic approaches (12). These efforts highlighted the phosgene—amine approach. Staudinger presented the stmctural similarities between isocyanates and ketenes and stimulated interest in this class of compounds (13). However, it was not until 1945, when the world was pressed for an alternative to natural mbber, that synthetic routes to isocyanates became an area of great importance. Several excellent review articles covering the synthesis and chemistry of isocyanates have been presented (1 9). 

Polymers produced by methods as described above have thermal stabilities many times greater than those obtained by the earlier bulk and solution methods of Staudinger. Staudinger had, however, shown that the diacetates of low molecular weight polyoxymethylenes (I) (polyformaldehydes) were more stable than the simple polyoxymethylene glycols (II) (Figure 19.2). 

Staudinger also found that diacetates of polyoxymethylenes with a degree of polymerisation of about 50 were less stable. Truly high molecular weight polyoxymethylenes (degree of polymerisation -1000) were not esterified by Staudinger this was effected by the Du Pont research team and was found to improve the thermal stability of the polymer substantially. 

STAUDiNGER, H., Die Hockmolekularen Organischen Verbindungen, Julius Springer, Berlin (1932). 

The story of Staudinger s researches and struggles against opposition, and also of the contributions of Carothers who is introduced in the next paragraph, is brilliantly told in a very recent historical study (Furukawa 1998). 

Furukawa, Y. (1998) Inventing Polymer Seience Staudinger, Carothers and the Emergence of Macromolecular Chemistry (Pennsylvania University Press, Philadelphia). 

Staudinger, H. (1932) Die Hochmolekiilaren Organischen Verhindungen (Springer, Berlin). 

Vinyl chloride (1835) formed by reacting acetylene with hydrochloric acid, was polymerized a.v polyvinyl chloride (PVC) in 1912, The theory of polymerization by Staudinger in the 1920s- led to the advances that followed. The acrylate were polymerized as polymethylmethacrylate to come into production in 1927. Polystyrene was developed. similarly and concurrently. Polyethylene came into production in 1939 for use in radar and now is ubiquitous. 

Universal SEC calibration reflects differences in the excluded volume of polymer molecules with identical molecular weight caused by varying coil conformation, coil geometry, and interactive propenies. Intrinsic viscosity, in the notation of Staudinger/ Mark/Houwink power law ([77]=fC.M ), summarizes these phenom-... 

FIGURE 16.10 Intial dextran calibration ( ) and resultingnb/Icbglucan calibration ( )forthe Sepha-cryl S-SOO/S-1000 (60 + 9S X 1.6 cm) system achieved from broad standard calibration with Dextran T-SOO and universal calibration, respectively Staudinger/Mark/Houwink constants (dextran Ksu = 0.0978 ml Mg . Osw = O.SO nb/lcb amylose = pullulan K pi. = 0.0268 ml M g . = 0.6S). 

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