The synthesis of polyvinyl chloride PVC from vinyl chloride monomer VCM involves a polymerization reaction, specifically a free radical chain-growth polymerization. Here is the step-by-step mechanism:1. Initiation: The process begins with the formation of free radicals, which can be generated using initiators such as organic peroxides or azo compounds. These initiators decompose upon heating, producing free radicals.Initiator 2 Free Radicals2. Propagation: The free radicals react with the vinyl chloride monomer, forming a new radical that can react with another vinyl chloride monomer. This process continues, leading to the formation of a growing polymer chain.Free Radical + VCM PVC RadicalPVC Radical + VCM PVC Radical with an additional VCM unit 3. Termination: The polymerization reaction is terminated when two growing polymer chains react with each other, or when a growing polymer chain reacts with a free radical or an initiator molecule.PVC Radical + PVC Radical PVC Chain + PVC ChainPVC Radical + Free Radical PVC ChainTo optimize the yield and purity of the final product, consider the following strategies:1. Control the reaction temperature: The polymerization reaction is exothermic, so controlling the temperature is crucial to avoid side reactions and degradation of the polymer. A temperature range of 40-60C is typically used.2. Use a suitable initiator: Choose an initiator with an appropriate decomposition temperature and half-life to ensure proper control of the reaction rate and molecular weight of the PVC.3. Optimize the initiator concentration: The concentration of the initiator affects the reaction rate and the molecular weight of the PVC. A higher initiator concentration leads to a faster reaction rate and lower molecular weight, while a lower concentration results in a slower reaction rate and higher molecular weight.4. Use a solvent or suspension polymerization technique: These methods help control the reaction rate and heat generation, as well as improve the purity of the final product by reducing the formation of impurities and side products.5. Purification: After the polymerization reaction, the PVC can be purified by washing with water to remove unreacted monomers, initiators, and other impurities. This can be followed by drying and sieving to obtain a high-purity PVC product.By optimizing these factors, you can increase the yield and purity of the synthesized polyvinyl chloride.