Optical activity anisotropy in thin films of chitosan L- and D-ascorbate

The specific optical rotation [α] of thin films of chitosan L- and D-ascorbate was studied. It was found that optical activity anisotropy occurs in the systems analyzed and [α] depends on the orientation angle θ of the film sample relative to the direction of the polarization vector of the incident light beam in the plane perpendicular to this beam. The angular dependences [α] = f(θ) (indicatrices) were processed to extract the constant term [α]₀ and four harmonics ([α]_i,  Fourier’s series) determined by structure elements with the corresponding symmetry, namely: the amorphous (isotropic) chitosan phase ([α]₀), irregular-shaped structures ([α]₁), rod-shaped ones in the film plane ([α]₂), helical ones  located perpendicular to the film surface ([α]₃), and crystalline structures ([α]₄).