Macromolecules in the Solid State

Most polymers are applied either as elastomers or as solids. Here, their mechanical properties are the predominant characteristics quantities like the elasticity modulus (Young modulus) E, the shear modulus G, and the temperature-and frequency dependences thereof are of special interest when a material is selected for an application. The mechanical properties of polymers sometimes follow rules which are quite different from those of non-polymeric materials. For example, most polymers do not follow a sudden mechanical load immediately but rather yield slowly, i.e., the deformation increases with time ( retardation ). If the shape of a polymeric item is changed suddenly, the initially high internal stress decreases slowly ( relaxation ). Finally, when an external force (an enforced deformation) is applied to a polymeric material which changes over time with constant (sinus-like) frequency, a phase shift is observed between the force (deformation) and the deformation (internal stress). Therefore, mechanic modules of polymers have to be expressed as complex quantities (see Sect. 2.3.5). 

The phenomenological ordering of polymers projected for use as constructing materials is not an easy matter. Sometimes the temperature stability is used as a criterion, i.e., the temperature up to which the mechanical properties remain more or less constant. Another attempt for classification, uses the E modulus or the shape of the curve of stress-strain measurements (see Sect. 2.3.5.1). In general one can say that semicrystalline thermoplastics are stiff, tough, and impact-resistant while amorphous thermoplastics tend to be brittle. Their E 

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In this section, initial spectral data on several polymers are reported to illustrate the utility of variable-temperature magic-angle spinning (VT-MAS) for the study of macromolecules in the solid state. 

This article reviews the behavior of photochromic macromolecules in the solid state and the problem has to be considered from two different points of view ... 

All of these compounds have many vacant orbitals at their disposal. They are therefore readily attacked, and in all of the common solvents they decompose into smaller units. For this reason they were previously not even considered to be macromolecules in the solid state. 

The main chain of dendronized polymers, due to die large size of the mon-odendrons, is usually forced to take a stretched shape thus the whole molecule exists as a rigid rod architecture both in solution and in the solid state.32d Depending on the backbone stiffness, the degree of monodendron coverage, and the size of die monodendron, the architecture of these macromolecules is no longer a sphere but a cylinder this dictates die properties of the dendronized polymers. 

This chapter draws a comprehensive picture of what has been done in the field of dendrimers with polymeric cores putting emphasis first on synthetic issues and then on experiments investigating the aggregation behavior of these intruiging macromolecules both in the solid state and on surfaces. Additionally, experiments will be described which show that some of these dendrimers can be considered cylindrical molecular objects. The macromolecules treated in this chapter may be considered as either dendrimers with polymeric core or alternatively dendronized polymers (or polymers with appendent dendrons) depending on whether one sees them from the vantage point of an organic or macromolecular chemist. 

This book gives a comprehensive coverage of the synthesis of polymers and their reactions, structure, and properties. The treatment of the reactions used in the preparation of macromolecules and in their transformation into cross-linked materials is particularly detailed and complete. The book also gives an up-to-date presentation of other important topics, such as enzymatic and protein synthesis, solution properties of macromolecules, polymer in the solid state. The content and presentation of Professor Vollmert s book is more encompassing than most existing treatises, and its numerous figures and tables convey a wealth of data, never, however, at the expense of intellectual clarity or educational value. 

Many studies, the first of which began shortly after the discovery of stereoregular polymerization of olefins, demonstrated that macromolecules could adopt stable helical conformations not only in the solid state but also in solution. These efforts have led to the realization that certain helical polymers reach a level of chiral recognition adequate for commercial development as an important aspect of chromatography. Researchers from the leading laboratory in this field, Okamoto, Yashima, and Yamamoto, have written Chapter 3 painting a detailed picture of the current status and future possibilities in this... 

Asakura, T., Kuzuhara, A., Tabeta, R., and Saito, H. (1985). Conformation characteriz-tion of Bombyx mod silk fibroin in the solid state by high-frequency 13C cross polarization-magic angle spinning NMR, x-ray diffraction, and infrared spectroscopy. Macromolecules 18, 1841-1845. 

With most solid polymers the G values for radical production, as determined by ESR, lie in the range 2 to 5. With biological macromolecules irradiated in the solid state comparable G values are obtained. 

For crystallizable macromolecules, what is their crystallography and morphology in the solid state ... 

Polyamides, like other macromolecules, degrade as a result of mechanical stress either in the melt phase, in solution, or in the solid state (124). Degradation in the fluid state is usually detected via a change in viscosity or molecular weight distribution (125). However, in the solid state it is possible to observe the free radicals formed as a result of polymer chains breaking under the applied stress. If the polymer is protected from oxygen, then alkyl radicals can be observed (126). However, if the sample is exposed to air then the radicals react with oxygen in a manner similar to thermo- and photooxidation. These reactions lead to the formation of microcracks, embritdement, and fracture, which can eventually result in failure of the fiber, film, or plastic article. 

In other words, isotactic macromolecules deriving from non-asymmetric monomers, spiraled in one screw sense only, might in principle exist in Hie solid state however on dissolution, it should be expected at least a partial despiralization, as well as the formation of sections spiraled in both screw senses, having equivalent average length, and hence the disappearance of optical activity, which in principle, might exist in the solid state. 

The speed with which NMR spectroscopy has been incorporated into scientific inquiry is truly amazing. The first commercial spectrometers became available in the 1950s. By the middle 1980s whole bodies could be placed in the probes of NMR spectrometers (magnetic resonance imaging) and the structures of body parts could be determined in exquisite detail. Today structures of proteins and other macromolecules in solution or in the solid state are determined routinely. What was unthinkable in the 1960s is routinely practiced today even by undergraduates The power of the method and the structural detail it provides have no doubt fueled its rapid development. 

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