Poly(ε‐Caprolactone)/Chitin and Poly(ε‐Caprolactone)/Chitosan Blend Films With Compositional Gradients: Fabrication and Their Biodegradability

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Abstract
Summary: Poly(ε‐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. Polarized optical microscopy micrographs of cross sections of (a) PI2lay, (b) PIgrad, (c) PO2lay, and (d) POgrad. magnified image Polarized optical microscopy micrographs of cross sections of (a) PI2lay, (b) PIgrad, (c) PO2lay, and (d) POgrad.