Polymer chemistry stereochemistry

In the preceding Sect. I have tried to illustrate the problems and developments of polymer stereochemistry from both the historical and logical points of view. A clear connection exists between synthetic and stmctural aspects For the solution of problems yet unsolved an interdisciplinary approach is required involving not only polymer chemistry but also spectroscopy, crystallography, statistical thermodynamics, solid state physics, and so on. 

To conclude this review I must pay a tribute to the work and figure of Giulio Natta who pioneered macromolecular stereochemistry and was an active protagonist in die field for many years. The most important aspects of his discoveries and the present significance of the research derived therefrom have been illustrated by his students and by scientists from all over the world (16, 18). As may be seen finom the present article, many of the fundamental discoveries were derived from the work of his research group at the Milan Polytechnic. A large part of the later development, also, is the fruit of a cultural tradition that has influenced the whole Italian school of polymer chemistry. 

The coupling of alkynes, an old field of polymer chemistry, is on new tracks resulting from defined metal-alkyl (39) and metal-carbene (40) catalysts [73, 74] previously simple metal halides (e. g. NbCls) of unspecified active catalyst structures were often employed. The polymer stereochemistry can be switched from 100% trans (R = t-Bu) to 100% cis (R = C(Cp3)2CH3) in the case of the imido(carbene) complex 40 upon making poly(2,3-bistrifluoromethyl)nor-bomadiene [74]. 

It is known that the physical properties of a polymer depend not only on the type of monomer(s) comprising it, but also on the secondary and tertiary structures, i.e., the stereochemistry of the linkage, the chain length and its distribution, its ability to crystallize or remain amorphous under various conditions, and the shape or distribution of the shapes of the chain in the crystalline and amorphous states. Through advances in polymer chemistry, in most cases polymers can be designed with specific properties. Control of the microstructure, e.g., the tacticity and molecular weight distribution of vinyl polymers, has been the focus of a number of papers in the last two decades. 

Harris, F. W. et al. State of the Art Polymer Chemistry. /. Chem. Educ. 1981,58, (Nov). (This issue contains 17pap>ers on jxjlymer chemistry. The series covers structures, properties, mechanisms of formation, methods of preparation, stereochemistry, molecular weight distribution, rheological behavior of polymer melts, mechanical properties, rubber elasticity, block and graft cojxjlymers, organometaUic polymers, fibers, ionic polymers, and polymer compatibility.)... 

Figure 7.12 Plots of qc vs. T for cholesteric aqueous solutions of short fragments of DNA, 5-dGMP, and dG4 Filled symbols refer to heating scans, while open symbols to cooling scans. While DNA and the G-wire of dG4 are right-handed, the G-wire of 5 -dGMP is left-handed Slopes and intercepts reflect the polymer stereochemistry. (Reprinted with permission of Wiley— VCH from Chemistry—A European Journal, Vol. 6, p. 3249 ad ff., copyright 2000.)...

There s a whole area of chemistry dealing with the spatial configurations of organic molecules called stereochemistry. To get into this area, you have to have molecules that have an asymmetrical carbon atom. That s one that has four dissimilar atoms or groups attached to it. PP has that condition on a repeating basis—the methyl groups on every ocher backbone carbon. Such a polymer can be stereoregular or stereospecific. 

Chapter 5, Polymer Synthesis, is probably most useful in a second-year chemistry course that touches on the topics of stereochemistry and some organic chemistry. 

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