The synthesis of polyvinyl alcohol PVA from vinyl acetate monomer VAM involves two main steps: the polymerization of vinyl acetate to form polyvinyl acetate PVAc and the hydrolysis of polyvinyl acetate to form polyvinyl alcohol.1. Polymerization of vinyl acetate to polyvinyl acetate:The polymerization of vinyl acetate is typically carried out through a free radical mechanism. This process can be initiated by heat, light, or chemical initiators, such as peroxides or azo compounds. The mechanism involves the following steps:a. Initiation: The initiator generates free radicals, which react with the vinyl acetate monomer to form a primary radical.Initiator 2 RR + CH2=CHOAc R-CH2-CHOAcb. Propagation: The primary radical reacts with another vinyl acetate monomer, forming a new radical. This process continues, leading to the growth of the polymer chain.R-CH2-CHOAc + CH2=CHOAc R-CH2-CHOAc-CH2-CHOAcc. Termination: The polymerization reaction is terminated when two radicals react with each other, forming a stable covalent bond.R-CH2-CHOAc + CHOAc-CH2-R R-CH2-CHOAc-CHOAc-CH2-RThe result of this polymerization process is polyvinyl acetate PVAc .2. Hydrolysis of polyvinyl acetate to polyvinyl alcohol:The conversion of polyvinyl acetate to polyvinyl alcohol is achieved through a hydrolysis reaction, which can be either acidic or basic. The mechanism involves the cleavage of the acetate group OAc and the formation of a hydroxyl group OH in its place.a. Acid-catalyzed hydrolysis:In the presence of an acid catalyst, the carbonyl group of the acetate is protonated, making it more susceptible to nucleophilic attack by water.R-CH2-C =O OAc + H+ R-CH2-C =O OH+OAcWater then attacks the carbonyl carbon, and the acetate group is eliminated as a leaving group.R-CH2-C =O OH+OAc + H2O R-CH2-C OH2 OH OAc R-CH2-C OH OH + OAc-b. Base-catalyzed hydrolysis:In the presence of a base, the hydroxide ion acts as a nucleophile, attacking the carbonyl carbon of the acetate group.R-CH2-C =O OAc + OH- R-CH2-C OH O- OAcThe acetate group is then eliminated as a leaving group, and a proton is transferred to the oxygen atom.R-CH2-C OH O- OAc R-CH2-C OH OH + OAc-The final product of this hydrolysis reaction is polyvinyl alcohol PVA .