STUDIES ON CHOLESTERIC LIQUID CRYSTALLINE TEXTURE OF CHITOSAN AND ITS DERIVATIVES WITH SURFACE TECHNIQUES

摘要

The cholesteric liquid crystalline structure in the chitosan/polyacrylic acid composite films is studied by surface techniques. A periodical lamellar-like structure is observed in the permanganic etched film surface by both scanning electron microscope (SEM) and atomic force microscope (AFM), instead of fingerprint texture which can be detected with polarized optical microscope. It is suggested that the periodical lamellar-like structure is induced by the etching selectivity between cholesteric layers due to different molecular arrangement on the film surface. Four kinds of perpendicular disclinations, i. e. x → τ~-+ λ~+, x → λ~- + τ~+ , x → τ~-+ τ~+ and x → λ~- + λ~+, are founded in the composite films with SEM. The smallest periodicity of lamellar-like structure (equals to half pitch) is 20～40 nm measured with AFM.