Polymer chain reaction

The repeating units of the engineering plastics also identify these as being predominantly condensation polymers, the class discussed in Chaps. 20 and 21. The commodity plastics are prime examples of the utility of the vinyl-type or chain reaction, polymers to be discussed here. 

Hamilton, S.C. and Semiyen, J.A., Cyclic Polyesters 5. Cyclic Prepared by Poly(decamethylene terephthalate) Ring-Chain Reactions, Polymer, 38,1685,1997. 

Wood BR, Semlyen JA, Hodge P. CycHc polyesters 4. CycHcs prepared by poly (decamethylene adipate) ring-chain reactions. Polymer. 1997 38 191-194. 

When solid polymer precipitates fiom bulk, solution, suspension, or emulsion polymerizations by a chain mechanism, the kinetics of the reaction and properties of the product may change sharply. If the solid phase is not swollen by the reaction mixture, the active site of the polymerization is isolated from possible termination reactions and may produce pronounced auto acceleration and increases in molecular weight of polymer formed. This behavior was quantified for one chain reaction polymer, polyvinyl chloride, covered in this book. Micldey (9) showed that polyvinyl chloride synthesis in bulk followed a two term kinetics equation with the second term representing incremental increases in polymerization rate due to accelerated polymerization in precipitated particles of polymer. 

Chain-reaction polymerizations (also referred to as addition polymerizations) require an initiator for polymerization to occur. Initiation can occur by a free radical, an anionic, or a cationic species. These initiators open the double bond of a vinyl monomer, and the reaction proceeds as shown above in Fig. 1.1. Chain-reaction polymers typically contain only carbon in their backbone and include such polymers as polystyrene and polyvinyl chloride. 

Carothers, in 1929, classified synthetic polymers into two classes, according to the method of their preparation, i.e., condensation polymers and addition polymers. In polycondensation, or step-growth polymerization, polymers are obtained by reaction between two polyfunctional molecules and elimination of a small molecule, for example water. Typical condensation polymers are shown in Figure 2. Addition (or chain reaction) polymers are formed from unsaturated monomers in a chain reaction. Examples of addition polymers are shown in Figure 2. 

Most synthetic polymers lie between these two extremes. Typical step-reaction polymers, such as polyesters, polyamides, polycarbonates, polsnirethanes, and cellulose esters, all contain hydrolyzable groups in the main chain. On the other hand, many chain reaction polymers, such as polyacrylonitrile, PMMA, and PVC, contain substituent groups which may hydrolyze at appropriate pH. 

Addition (or chain reaction) polymers are formed in a chain reaction of monomers which have doubles bonds. The following are examples of addition polymers ... 

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