Synthetic polymers from ionic polymerization

When many molecules combine the macromolecule is termed a polymer. Polymerization can be initiated by ionic or free-radical mechanisms to produce molecules of very high molecular weight. Examples are the formation of PVC (polyvinyl chloride) from vinyl chloride (the monomer), polyethylene from ethylene, or SBR synthetic rubber from styrene and butadiene. 

These Ionic reactions or electron transfer reactions are not what generally occur in the structure of both natural and synthetic polymers. In polymers it is the covalent bond that dominates, and in a covalently bonded structure there is no transfer of electrons from one atom to another. Instead the electrons are shared between the adjacent atoms In the molecule. The commercial polymeric materials that will be covered In this text will generally be based on seven atomic species silicon, hydrogen, chlorine, carbon, oxygen, nitrogen, and sulfur. Figure 2.4 shows these atoms with the number of outer valance electrons. 

PAN, a synthetic fiber, is a polymer of acrylonitrile monomers. Worldwide, 2.73 million tons of PAN are produced per year, of which over 98% are processed as filament yarn serving as material in the textile industry (Tauber et al., 2000). PAN usually has a molecular weight of 55,000-70,000 g mol and is most commonly a copolymer produced by radical polymerization from acrylonitrile, 5-10 mol% vinyl acetate (or similar nonionic comonomers) to disrupt the regularity and crystallinity, and ionic comonomers, such as sulfuric or sulfonic acid salts. PAN is a hydrophobic polymer that affects the processability of the fibers. The surface is not easily wetted. 

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