Fully‐Biodegradable Poly(3‐hydroxybutyrate)/Poly(vinyl alcohol) Blend Films with Compositional Gradient

Abstract

Abstract Summary: Fully‐biodegradable bacterial poly(3‐hydroxybutyrate) (PHB)/chemosynthetic poly(vinyl alcohol) (PVA) blend films with compositional gradient from one surface to the other surface of the films were prepared by a dissolution‐diffusion technique. Three kinds of PVA samples, high‐ and low‐molecular weight atactic PVA and highly syndiotactic PVA (s‐PVA), were used in order to investigate the effects of molecular weight and tactic structure on the generation of compositional gradient. The solution of PHB in 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP), which is also a good solvent for PVA, was cast on the PVA film and then the solvent HFIP was evaporated. By selecting the optimum volume of solvent and the evaporation rate, the PHB/PVA blend film with compositional gradient was obtained. The formation of compositional gradient was confirmed by FT‐IR microscopy and ATR‐FT‐IR analysis. The 50%/50% PHB/s‐PVA blend film with a nearly ideal compositional gradient, that is, the composition of PHB (or PVA) in the film changing gradually from 100% at one surface to 0% at the other surface of the film was obtained by casting PHB/HFIP solution on to the s‐PVA film. Positional dependence of the absorbance of CO and OH stretching bands along the film thickness direction for the PHB/S‐PVA cast films. magnified image Positional dependence of the absorbance of CO and OH stretching bands along the film thickness direction for the PHB/S‐PVA cast films.