Self‐organization of functional gradient structure in the biodegradable chitosan/poly(vinyl alcohol) blend film

Biologically inspired optimal structures combining the bioresorbable and bioactive properties are expected for the next generation of biomaterials. A compositional gradient structure was found to be spontaneously formed in the film of biodegradable chitosan/poly(vinyl alcohol) blend by casting aqueous solution on an aluminum dish. The formation of compositional gradient structure was confirmed by FTIR mapping measurement, DMTA measurement, and SEM observation on the freeze‐fractured cross section. In DMTA measurement, a broadening of the α‐relaxation curve corresponding to the glass transition was observed for the compositional gradient film, while a composition‐dependent single glass transition was observed for the homogeneous blend films. The resulted film with stable self‐organized compositional gradient exhibits novel physical properties inaccessible for the film of homogeneous blends obtained by casting from the same solution on a Teflon dish. The compositional gradient films present a unique combination of stronger stress and higher yield strain when compared with those of the homogeneous films at both dry and wet states.