Reactions of Macromolecules

Reactions are often carried out on macromolecules in order to elucidate their chemical structure. 

Macromolecular transformations are also of scientific and commercial interest. They can be used for the manufacture of new compounds, particularly in cases where no monomer exists (vinyl alcohol as the enolic form of acetaldehyde) or where the monomer polymerizes with difficulty or not at all (e.g., vinyl hydroquinone). In these cases, derivatives such as vinyl acetate or vinyl hydroquinone ester are polymerized and the polymers are then saponified to poly(vinyl alcohol) and poly(vinyl hydroquinone), respectively. Other processes of industrial importance are conversions of inexpensive macromolecular compounds such as cellulose into new materials (cellulose acetate, cellulose nitrate, etc.), manufacture of ion-exchange resins, and dyeing with reactive dyestuffs. All of these reactions lead to a definite product. If the degree of polymerization is retained, then they are called polymer analog reactions. 

Undesirable reactions are among those that occur during the more or less long-term applications of macromolecular materials exposed to the influence of atmospheric conditions (air, water, light, etc.). This aging, as it is called, to form undesirable products not only causes the constitution of the monomeric units to change (for example, through oxidation) it 

The reactions and properties of macromolecules are determined by chemical structure and molecular size. Consequently, it is convenient to use these parameters instead of, for example, mechanisms to classify macro-molecular reactions. Distinction is made among catalyses, isomerizations, polymer analog conversions, chain extension, and degradation reactions according to whether the chemical structure, the molecular weight, and/or the degree of polymerization are retained or changed. 

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A. Grafting Reaction of Macromolecules Having 4-Tolylcarbamoyl Pendant Group... 

Polymer oxidation is similar to oxidation of low-molecular-weight analogs in the liquid phase and has several peculiarities caused by the specificity of solid-phase free radical reactions of macromolecules. Several monographs are devoted to this field of chemistry [11,12,33-41],... 

LaMer, V. K., and T. W. Healy (1963), "Adsorption Flocculation Reactions of Macromolecules at the Solid-Liquid Interface", Rev. Pure Appl. Chem. 13, 112. 

Fundamental Reactions of Macromolecule-Metal Complexes in Solution. .. 106... 

In this review, however, only recent studies of the reactions of macromolecule-metal complexes will be reviewed. There have been some exellent reviews recently on macromolecule-metal complexes regarding syntheses, formation, characterization and catalytic activities l solar energy conversion 2), artificial oxygen carriers 3), and electrode processes 4). Furthermore, the preprints of the 1st International Conference on Macromolecule-Metal Complexes Tokyo Seminar on Macromolecule-Metal Complexes were published in 19875). These reviews and the preprints give useful information about the recent development of the basic and applied chemistry of macromolecule-metal complexes. 

A large number of investigations of the mechanism of electron transfer reactions of macromolecule-metal complexes in biological systems has been reported. These investigations were concerned with not only natural metalloenzymes such as cytochromes, ferredoxin, blue coppers, oxygenase, peroxidase, catalase, hemoglobin, and ruberodoxin, but also modified metalloenzymes 47). 

The Flory principle makes it possible in a simple way to relate the rate constants of the reactions of macromolecules (whose number is infinite) with the corresponding rate constants of elementary reactions. Since according to this principle all chemically identical active centers are kine-tically indistinguishable, the rate constant of the reaction between any two molecules is proportional to the rate constant of the reaction between their active centers and numbers of these centers in reacting molecules. Therefore, only a few rate constants of elementary reactions will enter in the material balance equations as kinetic parameters. 

Active centres and their residues (in non-stationary polymerizations) are always a source of unwanted reactions of macromolecules during further operations. On an industrial scale, radical centres are terminated by inhibitors. Even the inhibiting effect of atmospheric oxygen is exploited. 

The reaction of macromolecules with bifunctional anthracene-containing reagents, e.g. in the Friedel-Crafts reaction between the phenyl ring of polystyrene and... 

The decrese of the melting and crystallization temperatures of both PP and PE phases with an increasing concentration of peroxide cannot be ascribed to the increasing amount of crosslinks only, but, particularly, to other reactions of macromolecules. 

The effect of the solid body surface propagates a considerable distance from it that is, the influence of the surface on the chains that are in direct contact with it propagates via other chains into the bulk of the material. The range of action of the surface forces is a consequence of changes in the intermolecular interactions between chains that are directly adjacent to those in contact with the siuface. Two factors limit the molecular mobility of chains close to the boundary adsorption reactions of macromolecules with the surface and decrease of their entropy. Close to the boundary, the macromolecule cannot adopt the same number of conformations as in bulk, so that the surface limits the geometry of the molecule. As a result, the number of states available to the molecule in the smface layer decreases. These hmita-tions on conformation are the primary reason for the decrease of molecular mobility close to the boundary [32]. 

In consideration of various chemical reactions of macromolecules, the reactivity of their functional groups must be compared to those of small molecules. The comparisons have stimulated many investigations and led to conclusions that functional groups exhibit equal reactivity in both large and small molecules, if the conditions are identical. These conclusions are supported by theoretical evidence. Specifically, they apply to the following situations ... 

In principle, the chemical reactions of macromolecules should be similar to those of low-molecular-weight substances. Experimentally, however, either degradation is found to occur at very much lower temperatures or, occasion-... 

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