The Zn2+/chitosan blending system was investigated by tuning the Zn2+/chitosan ratios.First

the Zn2+/chitosan composite films were prepared by adding Zn(Ac)2#8226;2H2O into chitosan solutions.Then the structure

surface morphology

crystallization and thermal stability of the films were characterized with FTIR

XRD

DSC

DMA and AFM measurements.The FTIR results showed that coordination reaction occurred among the groups of —NH2

—OH

—NHCO—in chitosan and Zn2+

and this coordination reaction would play a crucial role in the subsequent characterizations.The coordination reaction occurred among the Zn2+

—NH2 and —OH groups was corroborated strongly by the FTIR measurements.The action between Zn2+ and —NH2 was evidenced by the disappearance of the 1630 cm-1 band(assigned to —NHCO—) and meanwhile the shift of the 1332 cm-1band (assigned to ν(C—N)); and the action between Zn2+ and —OH was reflected by the shift of 1066 and 1025 cm-1 bands (all are assigned to νas(C—OH)).The subsequent XRD and DSC results indicate further that the coordination would lead not only to the decrease in CS crystallization degree but also to the varia tion in the orientation of zinc acetic (ZnO) crystals.In addition

with more zinc acetic added

phase separation in solutions may take place also influence the CS crystallization.As the DMA revealed

that the tremendous phase separation would result in the significant decrease in the storage modulus.The size of chitosan crystal particles and the surface roughness of Zn2+/chitosan composite films increased with the content of Zn2+.Phase separation occurred between the chitosan and zinc acetate when the content of Zn2+reached a certain level

which led to obvious reduction of storage modulus of the composite film.