Effect of solvent on the microstructure of polyvinyl alcohol

The method for producing polyvinyl alcohol (PVA) by the solution polymerization of vinyl acetate first and then alcoholysis strategy is industrial. Where solvent plays a vital role in control over stereoregularity, molecular weight and its distribution, crystallinity and so on. In this report, when methyl acetate was used as a solvent in the polymerization of vinyl acetate instead of methanol, prepared PVA was characterized by Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results showed that PVA obtained in methyl acetate has a higher content of syndiotactic structure, crystallinity melting temperature and enhanced thermal stability compared with PVA obtained in methanol due to the formation of [PI] - [PI] complex between methyl acetate and vinyl acetate and the enhanced steric hindrance effect during polymerization. Additionally, methyl acetate has a smaller chain transfer constant (1.31 * [10.sup.-4]), which benefits to decrease the branching degree and molecular weight distribution index of PVA. This research provides more ideas for the choice of solvents in the industrial production of polyvinyl alcohol. KEYWORDS branching degree, molecular weight distribution, polyvinyl alcohol, tacticity, vinyl acetate
1 | INTRODUCTION Polyvinyl alcohol (PVA) is a biodegradable synthetic polymer with excellent characteristics including transparency, gas barrier property, water-solubility, mechanical properties, which has been widely used in various fields [...]