Optical activity anisotropy of chitosan-based films

• Published in: Carbohydrate polymers 2019-02, Vol.206, p.476-486
• Main Authors: Shipovskaya, Anna B., Shmakov, Sergei L., Gegel, Natalia O.
• Format: Article
• Language: English
• Subjects: Anisotropy; Chitosan; Optical activity
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2018.11.026

[Display omitted] •The phenomenon of optical activity anisotropy is characteristic of chitosan films.•The indicatrices of such films can be represented as Fourier series.•Each harmonic of the indicatrix corresponds to a certain supramolecular structure.•X-ray diffractometry data are in agreement with the assumed supramolecular structure. The optical activity [α] of films of chitosan and chitosan acetate was studied. [α] depended on the orientation angle θ of the film sample around the light beam. The angular dependences [α] = f(θ) (indicatrices) were processed to extract the constant term [α]0and four harmonics ([α]i, Fourier’s series) determined by structure elements with the corresponding symmetry: the amorphous (isotropic) phase of chitosan ([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). The contribution of individual supramolecular structures to the overall optical activity of chitosan was estimated: [α]2 and [α]4 predominated for the fresh chitosan acetate films, while [α]4 did for the chitosan ones. The results of the numerical decomposition of indicatrices are in satisfactory agreement with X-ray diffractometry data. The observed regularities predetermine prospects for obtaining stereoselective chiro-optic chitosan-based materials with novel functional properties.