Carrier structure chain growth

Chain growth differs from step growth in that it involves initiation and usually also termination reactions in addition to actual growth. This makes its kinetic behavior similar to that of chain reactions (see Chapter 9). However, the chain carriers in chain-growth polymerization need not be free radicals, as they are in ordinary chain reactions. Instead, they could be anions, cations, or metal-complex adducts. While the general structure of kinetics is similar in all types of chain-growth polymerizations, the details differ depending on the nature of the chain carriers. 

These polymers could not be crystallized, despite their apparent stereoregularity, probably because of the sterically-hindered character of the chains. It was proposed by Farina and Bressan62 that the chain growth was stereoregulated by the optically active anion of the ion-paired chain carrier. Further studies63 showed that the first portion of the polymer produced in a given reaction always possessed a less regular structure than later portions, unless the reaction was started in the presence of previously prepared polymer. This observation was interpreted as evidence for the pre-... 

Living polymerization is defined as chain polymerization in which chain termination and irreversible chain transfer are absent. The rate of chain initiation is usually larger than the rate of chain propagation with the result that the number of kinetic-chain carriers is essentially constant throughout the reaction. Reversible (temporary) deactivation of active centers can take place in a living polymerization, and all the macromolecules formed possess the potential for further growth. The term controlled polymerization, on the other hand, indicates control of a certain kinetic feature of a polymerization or structural aspect of the polymer. ... 

The most complete structural information about sulfate-dependent protein interactions is available from extensive studies on the many interactions of heparan sulfate proteoglycans (HSPGs). Via their covalently attached heparan sulfate chains, HSPGs bind to a large array of growth factors, cytokines, chemokines, extracellular matrix proteins, cell-cell adhesion molecules, viral attachment receptors, blood coagulation components, and lipid carrier molecules [18 21], Among the functions served by these interactions are ... 

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