Chain Alignment of a Rigid Ring Polymer in the Lyotropic Liquid Crystal Phase: Cyclic Amylose Tris(n-butylcarbamate) in Tetrahydrofuran and Ethyl Lactate

Concentrated solutions of a rigid ring polymer, cyclic amylose tris(n-butylcarbamate) (cATBC), have lyotropic liquid crystallinity. Phase boundary concentrations of cATBC in tetrahydrofuran (THF) and l-ethyl lactate (EL) were almost identical to those for the linear polymer (ATBC) with the same molar mass. X-ray diffraction for the concentrated cATBC solutions revealed that nematic phases were found for cATBC in the two solvents, while the cholesteric structure was observed for the cATBC-EL system. Several peaks were found in the high q range between 3 and 10 nm-1 with q being the magnitude of the scattering vector. The obtained patterns were almost the same as that for an ATBC sample in the corresponding solvent, indicating that the local alignment of the polymer chains is similar between the ring and linear polymers. This result strongly suggests that cATBC chains in concentrated solutions form a pseudo-rodlike conformation with two kinks, whereas cATBC chains behave as semirigid rings in dilute solution. The phase diagram can be also explained in terms of the known theory for the wormlike cylinder, assuming the pseudo-rodlike conformation.