Effects of polyphenols on the thermal decomposition, antioxidative, and antimicrobial properties of poly(vinyl alcohol) and poly(vinyl pyrrolidone)

Thermal stabilizers are frequently employed to increase the thermal stability of polymers. Among the thermal stabilizers, the polyphenols and related molecules have been widely used as thermal stabilizers of polymers. However, the effect of the number of their phenolic hydroxyl groups on the thermal decomposition of polymers was relatively less studied. In this study, three phenolic compounds with different numbers of phenolic hydroxyl groups (phenol, pyrocatechol, and pyrogallol) were incorporated in water-soluble poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) to fabricate the polymer/phenolic additive composite films. The effects of the phenolic additive on the thermal decomposition of PVA and PVP were investigated through thermogravimetric analysis. The results suggested that the phenolic additive is effective as a thermal stabilizer, owing to its radical-trapping action, when its boiling point is higher than the thermal decomposition temperature of the polymer (PVA and PVP) and the polymer decomposition follows a radical pathway. In addition, to compare the effect of the number of phenolic hydroxyl groups in the phenolic additive on the properties of the composite films, their antioxidative and antibacterial activities were evaluated using the alpha,alpha-diphenyl-beta-picrylhydrazyl assay and disk diffusion test, respectively.