Poly(ε-caprolactone)/chitin and poly (ε-caprolactone)/chitosan blend films with compositional gradients:: Fabrication and their biodegradability

Poly(e-caprolactone) (PCL)/chitin and PCL/chitosan blend films with compositional gradients were successfully fabricated by a dissolution/diffusion Method; that is, repeatedly pouring the PCL/chitin (or PCL/chitosan) blend solutions, with variable composition, onto polysaccharide layers. The compositional gradient structure in the resulting films was characterized by polarized optic microscopy, ATR-FT-IR and trans-FT-IR microscopic spectroscopy. Enzymatic degradability of the PCL/chitin and PCL/chitosan blend films with compositional gradients in the presence of lysozyme was compared with those of homogeneous films and two-layer films. It was found that the degradation rate of PCL/chitin blend films with a compositional gradient was far lower than that of the neat chitin film, whereas the degradation rate of PCL/chitosan blend films with a compositional gradient was close to that of the neat chitosan film. The Suppression of the chitosan crystallization. which accelerates the enzymatic degradation, at the Surface of PCL/chitosan films with a compositional gradient was much more severe than that for PCL/chitin films with a compositional gradient.