Electron microscopic evidence for cholesteric structure in films of cellulose and cellulose acetate

This is the authors' abstract. We don't add key points for this paper.

Many cellulose derivatives form lyotropic and thermotropic cholesteric liquid crystalline phases.1s2The formation of these ordered phases is generally attributed to the relative stiffness of the cellulose chain's3 and by this criterion cellulose itself should also form liquid crystalline solutions in those few solvents in which it dissolves.(A thermotropic liquid crystalline phase is unlikely because, on heating pure cellulose, it decomposes before melting.)However, the evidence for a lyotropic liquid crystalline phase of pure cellulose is somewhat equivocal; observations in N-methyl morpholine N-~xide/water,~ in trifluoroacetic acid/chlorinated alkanes,5 and in lithium chloride/ N,N-dimethyl a ~e t a m i d e ~. ~ do indicate formation of anisotropic solutions, but because of the strong tendency of cellulose to aggregate or crystallize, the fluid liquid crystalline state is often metastable?Under some conditions, solid films prepared from cholesteric liquid crystalline phases may retain the helicoidal supramolecular structure that is characteristic of cholesteric fluids?(Hydroxypropyl)cellulose, when cast from aqueous solution, forms cholesteric films" that, on heating, preferentially reflect circularly polarized light at