Cholesteric pitch with time, change

Elimination of the solvent from cholesteric solutions of polypeptides is usually not accompanied by destruction of the cholesteric structure. As Fig. 7.4 suggests, only a change in the pitch is observed when the concentration of polymer in the solution increases, and when the solvent is evaporated, the polymer films of polypeptides become colored as soon as the pitch of the cholesteric helix becomes commensurate with the wavelength of the reflected light. The rod-like macromolecules of polypeptides usually lie in the plane of the film and the axes of the cholesteric helices are chaotically positioned in this plane. At the same time, there are data which indicate Ae formation of crystalline films of polypeptides from a number of solvents (for example, the PBG-L-dimethylformamide system) in some cases, the formation of an unordered amorphous structure is also possible (for example, as in the presence of trifluoroacetic acid). 

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