Miscibility characterization of zein/methacrylic acid copolymer composite films and plasticization effects

Composite films have gained interest for producing films with optimal properties, without the need of chemical modification. Miscibility of components in the film is important for attaining reproducible and consistent film properties. This study used several techniques, i.e. differential scanning calorimetry, Fourier transform infrared spectroscopy and Raman spectroscopy to understand the degree of miscibility of components and its impact on morphology and mechanical properties of the composite film prepared by casting the blend of zein and methacrylic acid copolymer (Eudragit® L100-55). The effects of composition and plasticization by triethyl citrate and polyethylene glycol 1000 were explored. The results demonstrate the miscibility of zein and methacrylic acid copolymer at a molecular level; and the phase behavior of polymer blends is modified by plasticization. Polyethylene glycol 1000 is more compatible with the polymer blend. Its plasticization effect is associated with an increase in β-sheets. Understanding the miscibility between the plasticizer and the polymer blend allows the ability to predict and control mechanical properties of the zein/methacrylic acid copolymer composite film, in particular when the plasticizer level is changed.