Since the monomer of poly(vinyl alcohol), vinyl alcohol, is nonexistent — the tautomeric equilibrium lies on the acetaldehyde side — only indirect methods are available for the production of poly(vinyl alcohol). The most important manufacturing process for poly(vinyl alcohol), which is used worldwide, is the polymerization of vinyl esters or ethers, with subsequent saponification or transesterification.Nowadays, PVOH in industrial applications is generally obtained from the saponification or hydrolysis of homopolymer of VAc.PVOH properties depend on degree of the hydrolysis as well as the primary structures of the original precursor of poly(vinyl acetate) (PVAc), such as head-to-tail regioselectivity, molecular weight, and tacticity.
Therefore, from the viewpoint of synthetic chemistry, the control of the VAc polymerization is still a challenging topic to improve the properties of PVA and further contributes to the development of the PVA-based materials as well as the new polymerization systems for other protecting monomers.vinyl acetate (VAc) monomer can be polymerized with bulk, solution, emulstion and suspension polymerization processes. However, there are some technical restrictions in the industrial practice. The heat of polymerization of VAc monomer has been determined too high to be controlled during the process. The difficulty of removing the heat of polymerization and therefore of controlling the polymerization reaction, as well as the occurrence of branching at high polymer-monomer ratios which can lead to in solubilization of the polymer, have made bulk polymerization unattractive.
Commercially, solution polymerizations are preferred when the poly-VAc is to be sold as a solution polymer directly, for example, for adhesive applications in ethyl acetate or toluene solvents, or when the PVAc is only an intermediate product as it is in polyvinyl alcohol preparation in methanol solvent.
