Macromolecules specific properties

Our research in this field is mainly carried out on a) synthesis and conversion of oligoorganoepoxystannanes b) free-radical copolymerization of organotin monomers with various vinyl monomers and c) cross-linking of organotin macromolecules and development of protective polymeric coatings with specific properties on their basis. 

Polymers have some specific properties due to their organic nature. Thermoplastics, as seen in Chapter 1, are independent organic macromolecules with some sensitivity to environmental parameters temperature, moisture, deleterious solids, liquids, gases and other chemical products. They are also sensitive to mechanical loading, especially cyclic loads. Their specific properties, such as electrical or optical properties, are also important for their applications. 

World War II helped shape the future of polymers. Wartime demands and shortages encouraged scientists to seek substitutes and materials that even excelled those currently available. Polycarbonate (Kevlar), which could stop a speeding bullet, was developed, as was polytetrafluoroethylene (Teflon), which was super slick. New materials were developed spurred on by the needs of the military, electronics industry, food industry, etc. The creation of new materials continues at an accelerated pace brought on by the need for materials with specific properties and the growing ability to tailor-make giant molecules macromolecules—polymers. 

Some specific properties of macromolecules are employed for the detection in polymer HPLC. It is primarily the large size of detected species, which is comparable with the wavelength of the visible light. As a result, the light beam interacting with the macromolecules is intensively scattered [272]. The extent of light scattering under otherwise constant experimental conditions depends on the molar mass of macromolecules. 

For selection of a chromatographic method it should be taken into consideration whether the protein of interest may be denatured (or if it can be renaturated) or some specific properties as ligand binding or enzymatic activity must be conserved during purification. These reflections are not relevant, if during analytical separation a signal produced by a covalently attached label is measurable independent of the structure of the macromolecule. 

Synthesis of well defined functionalized (- telechellc or multifunctional-) macromolecules Is an Important task for polymer chemists. The polymers with P0(0R)2, - Si(0R)3, -OH, - . .. functional groupslrS. are produced In limited quantities. The need for polymeric materials possessing specific properties has led to a renewed Interest Is functional polymers, especially if the initial material Is a common hydrocarbon polymer. One of the techniques that we use in our laboratory to prepare these new molecules Is based on anionic processes. This anionic technique is best suited to control the length of the chains prepared and to obtain samples with low polydlsperslty. Although the functionalization of carbanionic sites with various deactivating reagents Is easier than with other methods because of the long lived species, It Is still necessary to carefully control the deactivation reaction to prevent secondary reactions. 

Cyclolinear structure of synthesized POCS-4, POCS-5 and POCS-6 polymers was proved by hydro-dynamic study of properties of their solutions [56], The expected results of these investigations should indicate the predominant influence of the equilibrium flexibility of macromolecules and other specific properties of polymeric chains in block on occurrence of the thermotropic mesophase in cyclolinear organosiloxanes. 

In much the same way, natural polymeric fibers like wool, cotton, silk, etc., are often touted as superior to anything that is man-made or synthetic. But is this fair There is no doubt that natural fibers have a unique set of properties that have withstood the test of time (e.g., it is difficult, but not impossible, to match silk s feel or cotton s ability to breathe ). On the other hand, consider Lycra , a completely synthetic fiber produced by DuPont (Figure 1-12) that has a truly amazing set of properties and is the major component of Spandex (a material that keeps string bikinis on ). Or consider the wrinkle-free polyester fibers used in clothing and the stain proof nylon and polyacrylonitrile polymers used in carpets. The point here is that polymers, be they natural" or synthetic, are all macromolecules but with different chemical structures. The challenge is to design polymers that have specific properties that can benefit mankind. 

The large number of variables involved in complex coacervation (pH, ionic strength, macromolecule concentration, macromolecule ratio, and macromolecular weight) affect microcapsule production, resulting in a large number of controllable parameters. These can be manipulated to produce microcapsules with specific properties. Complex coacervate microcapsules have been formulated as suspensions or gels, and have been compounded within suppositories and tablets.[ l... 

As mentioned, molecular and mesoscopic approaches will be needed. The first part of the book mainly considers molecules. We start with some basic thermodynamics, interaction forces, and chemical kinetics (Chapters 2-4). The next chapter is also concerned with kinetic aspects it covers various transport phenomena (which means that a few mesoscopic aspects are involved) and includes some basic fluid rheology. Chapters 6 and 7 treat macromolecules Chapter 6 gives general aspects of polymers and discusses food polysaccharides in particular, with a largish section on starch Chapter 7 separately discusses proteins, highly intricate food polymers with several specific properties. Chapter 8 treats the interactions between water and food components and the consequences for food properties and processes. 

Almost all foods contain macromolecules and almost all of these macromolecules are polymers. Polymers have specific properties, warranting a separate treatment some aspects of them are discussed in this chapter. 

A microparticle is defined as a physical object whose wave properties can be registered. This class includes elementary particles, atomic nuclei, atoms (atomic ions), molecules (molecular ions) and more complex assemblies (like clusters and macromolecules). Some properties of microparticles belong to the universal physical constants (energy, mass, linear momentum, angular momentum, electric charge, magnetic moment) some, on the contrary, are exclusively specific for microparticles (spin, parity, life-time). Macroscopic state properties (such as temperature, pressure, volume, entropy, etc.) are irrelevant for a single microparticle. 

The most specific property of plasma-polymerized films is a high concentration of free radicals in the films and a large niunber of cross-links between macromolecules. The... 

Polymer solutions differ from those of low-molecular-weight matter by specific properties of macromolecules characterized by large size, broad molecular-mass distribution, flexibility range, numerous conformations and capability of conformal recombinations in response to temperature fluctuations and solvent type [29]. 

Film formation is a specific property of polymers that distinguishes them from low-molecular matter. This is a considerable length and asymmetry of macromolecules capable of forming a strong oriented permolecular structure during stretching of polymer bodies that lies at the base of this property [2]. So far, polymers are considered to utterly suit to a raw material for production of the films. 

Nature shows how complicated it is to construct metal-containing macromolecules that are active but also selective with respect to a specific property. Natural systems do not need to exhibit a high stability towards storage and heat because the active materials are readily replaced. On the other hand, artificial systems must be more stable over time and towards heat. Therefore extreme demands are placed upon artificial metal-containing macromolecules. It IS important to point out that the fundamental behaviors of low molecular weight metal complexes will be shown also in macromolecular analogues. But these behaviors, and thus the properties, are strongly influenced by the kind of macromolecular environment or the kind of incorporation into a macromolecule. 

The mesostructure covers both the macromolecular scale (dimension, conformation and architecture of the macromolecules) and also the supramole-cular scale (complex aggregates between macromolecules). It is this last point that is the key to the specific properties of natural rubber. This associative... 

Taking into consideration that all these different ionogenic groups each characterised by its specific properties, if situated at the surface of the corpuscular macromolecule, may occupy different relative positions, it will be evident that the corpuscular proteins cannot at all be considered as a simple case, suitable for startii a discussion on the significance of characteristic charge elements. 

Functional Macromolecules. Functional macromolecules bear chemical groups, which differ in composition from the main polymer chain. The functional groups lend to polymer chains some specific properties, for example certain reactivity. This property is especially important for oligomers. 

Very specific properties, thus, can be achieved with these funny polymers. The question of nomenclature, however, is for most of them formidable. New rules or naming must be formulated to satisfy the goal to have not only an empirical name for a polymer, but to be able to systematically link a name to the chemical structure of the macromolecule. 

Both stmcture and macromolecular d5mamics render the significant influence on its stability, i.e., chemical nature of the solvent (plasticizer), its basicity, specific and non-specific solvation, degree of PVC in a solution (solubility), segmental mobility of macromolecules, thermodynamic properties of the solvent (plasticizer), formation of associates, aggregates, etc. 

It is worth noting that all these latter examples of materials whose key feature calls upon a specific behaviour of furan moieties, require modest contributions from these heterocycles in terms of its quantitative presence in the macromolecules. This situation is similar to that described in Section 6.5.2, in which furan derivatives were used to modify the end groups of some polymers or to synthesize block copolymers by cationic polymerization. In both instances, therefore, it is not the dominant presence of the heterocycle that determines the specific properties of the final materials (as in the case of polymers and copolymers bearing furan monomer units), but instead the fact that a small or even minute percentage of these structures introduces an original mechanistic feature, associated with the peculiar chemistry of the heterocycle, which transforms the behaviour and properties of the final material. This crucial point will be met again in the context of the application of the DA reaction in Section 6.8. 

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