Reactivity of macromolecules

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 [1, 2]. Specifically, they apply to the following situations [1]  

Reactions that take place in homogeneous fluid media with all reactants, intermediates, and end products fully soluble. These conditions exist from the start to the end of the reactions. 

All elementary steps involve only individual functional groups. The other reacting species are small and mobile. 

The steric factors in the low molecular weight compounds selected for comparison must be similar to those of the large molecules. 

Principles of Polymer Chemistry, DOI 10.1007/978-l-4614-2212-9 9, 1st and 2nd editions (C) Kluwer Academic/Plenum Publishers 1995, 2000, 

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The above statement must not be taken in a pejorative sense. It is agreed that a knowledge of the component systems is a condition sine qua non. But only as long it is realized that the theoretical study of a macromolecule should be undertaken by a quantum statistical method, after the individual systems have been fully studied. In this connection, the theories developed in the quantum mechanical treatments of fluids and solids can be of use. The ultimate purpose is the development of a theory that will account for the specific reactivity of macromolecules. 

Discuss the effect of diffusion-controlled reactions on the reactivity of macromolecules. 

M. Went, R. Evans and D. H. Napper, J. Polym. Sci., Polym. Symp. 159-167 (1975), "The Chemical Reactivities of Macromolecules Attached to an Interface". 

The reactivity of macromolecules depends largely on the stage in which they are present and the high order structure as well as the primary structure and functional groups in the structure. In designing macromolecules, therefore, not only the position of func-... 

Adhesion is usually controlled by means of various finishing agents. Mikhalsky noted in [260] that reactions between such agents and thermoplastics are hindered for a number of reasons, one reason being that the chemical structure of the polymer is formed before the treated filler is added. In the majority of cases thermoplastics do not contain reactive groups, if perhaps only at the ends of macromolecules where they enjoy little mobility. The probability of contact between the reactive groups of the agent and the plastic. 

The observed differences in the reactivity of the nitrile groups in the macromolecules of the copolymers can be explained by an intramolecular nucleophilic interaction of the nitrile groups with the adjacent functional groups applying the same point of view as for adjacent nitrile groups ... 

Interest in anionic polymerizations arises in part from the reactivity of the living carbanionic sites4 7) Access can be provided to polymers with a functional chain end. Such species are difficult to obtain by other methods. Polycondensations yield ro-functional polymers but they provide neither accurate molecular weight control nor low polydispersity. Recently Kennedy51) developed the inifer technique which is based upon selective transfer to fit vinylic polymers obtained cationically with functions at chain end. Also some cationic ring-opening polymerizations52) without spontaneous termination can yield re-functional polymers upon induced deactivation. Anionic polymerization remains however the most versatile and widely used method to synthesize tailor made re-functional macromolecules. 

Another kind of situation arises when it is necessary to take into account the long-range effects. Here, as a rule, attempts to obtain analytical results have not met with success. Unlike the case of the ideal model the equations for statistical moments of distribution of polymers for size and composition as well as for the fractions of the fragments of macromolecules turn out normally to be unclosed. Consequently, to determine the above statistical characteristics, the necessity arises for a numerical solution to the material balance equations for the concentration of molecules with a fixed number of monomeric units and reactive centers. The difficulties in solving the infinite set of ordinary differential equations emerging here can be obviated by switching from discrete variables, characterizing macromolecule size and composition, to continuous ones. In this case the mathematical problem may be reduced to the solution of one or several partial differential equations. 

This is the simplest of the models where violation of the Flory principle is permitted. The assumption behind this model stipulates that the reactivity of a polymer radical is predetermined by the type of bothjts ultimate and penultimate units [23]. Here, the pairs of terminal units MaM act, along with monomers M, as kinetically independent elements, so that there are m3 constants of the rate of elementary reactions of chain propagation ka ]r The stochastic process of conventional movement along macromolecules formed at fixed x will be Markovian, provided that monomeric units are differentiated by the type of preceding unit. In this case the number of transient states Sa of the extended Markov chain is m2 in accordance with the number of pairs of monomeric units. No special problems presents writing down the elements of the matrix of the transitions Q of such a chain [ 1,10,34,39] and deriving by means of the mathematical apparatus of the Markov chains the expressions for the instantaneous statistical characteristics of copolymers. By way of illustration this matrix will be presented for the case of binary copolymerization ... 

In particular, the electron density distribution and the dynamic properties of this density determine both the local and global reactivities of molecules. High resolution experimental electron densities are increasingly becoming available for more and more molecules, including macromolecules such as proteins. Furthermore, many of the early difficulties with the determination of electron densities in the vicinity of light nuclei have been overcome. 

Contents Structure and reactivity of monomeric, molecular tin(ll) compounds / M. Veith, O. Recktenwald — Chirality, static and dynamic stereochemistry of organotin compounds / M. Gielen — Coordination effects in formation and cross-linking reactions of organotin macromolecules / Z. M. O. Rzaev. 1. Organotin compounds — Addresses, essays, lectures. I. Gielen, M. (Marcel), 1938 — II. Series. 

By varying all the parameters of the process the authors prepared a set of copolyesters containing units and blocks with a tertiary amino group, which, in turn, could be transformed into a hydrophilic hydrochloride salt thus imparting water-compatibility to the initially organosoluble macromolecules. The principle involved was the formation of a block-type structure of chains in order to facilitate their further protein-like folding in an aqueous medium. It was shown that the main factors responsible for the blockiness were the relative reactivities of the (B) and (C) components (NMDEA and bisphenol) and the order of their addition to the reaction. 

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