Synthetic techniques step-growth polymerization

The first synthetic functional polymers were developed in the early days of the twentieth century already. They were prepared using standard polymerization techniques like free radical or step-growth polymerization reactions. The increased material needs in modem technology and the increased complexity of polymeric materials, however, led to a strong expansion of this field especially in recent years. Today s synthetic techniques allow a much better control of the polymers stmcture. 

In contrast to the limitations of the step-growth polymerization techniques, ring-opening polymerization (ROP) of cyclic esters may provide high-molecular-weight aliphatic polyesters (up to lOOkgmol" ) under mild conditions. " ROP is the prefened synthetic pathway used in industry, and... 

A step-growth synthetic method for incorporating metal clusters into polymers was shown in Eq. 7.9. And, in the preceding section, metal clusters were incorporated into polymers and oligomers using bidentate ligands and the techniques of coordination polymerization. Yet a third synthetic route to these materials is to react selected metal clusters with acetylenes.13,38,39,40 In many such reactions, the two carbons of the acetylene unit are incorporated into the metal cluster. An example is shown in Eq. 7.32. 

Two primary methods are commonly used to convert monomers into synthetic polymers. In the older literature, these techniques are referred to as addition and condensation polymerization, but because of ambiguities in these terms, the preferred names now are chain-reaction polymerization and step-growth... 

Biomacromolecules such as proteins derive their function from their three-dimensional shape and the precise functional group placement on the surface and interior of the structure. Also known as the tertiary structure, this shape is a result of a perfectly controlled monomer sequence, or primary structure. Synthetic polymers containing a perfect monomer sequence are inaccessible using contemporary techniques. However, recent advances in polymerization techniques allow for the fabrication of multi-block polymers with narrow molecular weight distributions " and materials with relatively controlled monomer sequences by step-growth and chain-growth... 

Abstract Polymers are macromolecules derived by the combination of one or more chemical units (monomers) that repeat themselves along the molecule. The lUPAC Gold Book defines a polymer as A molecule of high relative molecular mass, the structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass. Several ways of classification can be adopted depending on their source (natural and synthetic), their structure (linear, branched and crosslinked), the polymerization mechanism (step-growth and chain polymers) and molecular forces (Elastomers, fibres, thermoplastic and thermosetting polymers). In this chapter, the molecular mechanisms and kinetic of polymer formation reactions were explored and particular attention was devoted to the main polymerization techniques. Finally, an overview of the most employed synthetic materials in biomedical field is performed. 

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