Preparation and properties of polyvinyl alcohol composite films by incorporation of coumarin-3-carboxylic acid modified silica

Polyvinyl alcohol (PVA) exhibits excellent film-forming properties, but the limited functionality restricts its broader practical applications. To improve the poor water resistance and lack of antibacterial activity of polyvinyl alcohol (PVA) films, series composites were prepared by using coumarin-3-carboxylic acid (CCA) grafted onto silica nanoparticles (CCAS) and then introduced into PVA matrix along with a plasticizer (PEG). The results showed that the maximum tensile strength of the composite film was increased by 94 %, while its good plasticity was preserved. As the CCAS content in the PVA matrix increased, the composite film presented raised water contact angle but decreased water vapor transmission coefficient, indicating an improvement in water resistance. However, excessive CCAS would affect the films from the aspects of opacity plus mechanical properties. In addition, the UV-shielding ability of the composite films was close to 100 %, which exerted an inhibitory effect on the growth of Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ) (≥90 %). In particular, the inhibition rate against S. aureus was as high as 94 %. Compared with PVA film, the composite films exhibited superior mechanical properties, optical properties, antibacterial activity, and water vapor barrier properties, making them more promising for practical applications.