Lyotropic Liquid Crystallinity of Linear and Cyclic Amylose Derivatives: Amylose Tris(<i>n</i>‑octadecylcarbamate) in Tetrahydrofuran and 2‑Octanone

Abstract

Lyotropic liquid crystallinity was examined for 8 linear amylose tris­(n-octadecylcarbamate) (ATODC) samples ranging in the weight-average molar mass (Mw) from 25 to 1510 kg mol–1 and 10 cyclic ATODC (cATODC) samples, the Mw of which varies between 36 and 191 kg mol–1. Appreciable cholesteric patterns were not observed in the concentration range investigated. Diffraction data from small-angle X-ray scattering both for bulk polymer samples at 160–180 °C and concentrated solutions at 25 °C indicate that no characteristic peaks were found except for a broad diffraction reflecting the chain distance between the neighboring polymer molecules. The phase boundary concentrations for ATODC and cATODC in tetrahydrofuran and 2-octanone were determined at 25 °C as a function of Mw. The obtained phase diagram for ATODC was well fitted by a conventional scaled particle theory (SPT) for the wormlike spherocylinder as in the case of the other stiff polymer systems. On the other hand, when we assumed that cATODC chains form a rodlike structure in the nematic phase, the experimental data were successfully explained by a modified SPT, suggesting that conformation of cATODC in the nematic phase is different from that in dilute solution