CHOLESTERIC LIQUID CRYSTALLINE CHARACTER ON THE SURFACE OF CHITOSAN/POLYACRYLIC ACID COMPOSITES*

 The cholesteric liquid crystalline structure in chitosan/polyacrylic acid composite films was studied by surfacetechniques. A periodical lamellar-like structure was observed in the permanganic acid etched film sufface by both scanningelectron microscopy (SEM) and atomic force microscopy (AFM), instead of the thumb-print texture which can be detectedwith polarized optical microscopy. It is suggested that the periodical lamellar-like structure is induced by the etchingselectivity between cholesteric layers due to different molecular arrangement on the film surface.Four kinds of perpendicular disclinations,i.e. χ→τ^-+λ⁺,χ→λ^-+τ⁺,χ→τ^-+τ⁺ and χ→λ^-+λ⁺, were found in the composite films from SEM observations.The smallest periodicity of lamellar-like structure(equals to half pitch)is 20～40 nm measured with AFM.