Enhancing the compatibility of poly(vinyl alcohol)/starch and its composite film properties using a new...

The heterogeneous dispersion of starch and polyvinyl alcohol (PVA) in solution often leads to phase separation in the resulting starch/PVA blend film, adversely affecting its mechanical and barrier properties. To address this issue, corn starch was functionalized via vinyl acetate grafting using electron transfer atom transfer radical polymerization, yielding a DES-g-(PVAc)₂ with a branched structure analogous to that of PVA. This esterified-grafted starch was used to partially replace acid-thinned starch (ATS), and the effect of the DES-g-(PVAc)₂ mass ratio on sedimentation behavior and initial phase separation time was investigated. Composite films were prepared, and the effect of incorporating DES-g-(PVAc)₂ on the film properties was evaluated by assessing thermal stability, tensile properties, moisture sensitivity, swelling degree, water vapor permeability (WVP), and oxygen barrier property. The results demonstrate that graft copolymerization significantly enhances the compatibility between starch and PVA. As the DES-g-(PVAc)₂ mass ratio increased from 0% to 40%, the tensile strength of the composite film increased from 27.6 MPa to 31.1 MPa, while the contact angle increased and both moisture regain and swelling degree decreased. Moreover, the WVP decreased from 5.75 × 10^-4 g·m^-1·m^-2·h^-1·kPa^-1 to 4.07 × 10^-4 g·m^-1·m^-2·h^-1·kPa^-1, and the oxygen transmission rate decreased from 3.96 cm³/m²·24h to 1.28 cm³/m²·24h. The incorporation of DES-g-(PVAc)₂ effectively enhances the compatibility of starch and PVA, leading to superior mechanical and barrier properties of the composite films.