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

Abstract

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.

Molecular Conformation and Intermolecular Interactions of Linear and Cyclic Amylose Derivatives in Solution

“…[ 46 ] Unfilled triangles, cATBC. [ 46,48 ] Filled squares, cADMPC, [ 42 ] filled inverse triangles, cATODC. [ 20 ] a) The ratio of the h values for ring and linear plotted against the reduced chain length ( L / L k ) linear for the corresponding linear chain.…”

“…[64] On the other hand, Avendano et al [2] predicted theoretically that the rigid nanorings can form smectic mesophase at low concentration. We thus determined isotropicliquid crystal phase boundaries and X-ray diffraction pattern of the concentrated solutions of cATBC [48] in THF and EL and cATODC [65] in THF and MHK. Figure 8 shows the M w dependence of the phase boundary concentrations c I and c A for cATBC and cATODC in THF along with those for the linear chains, [66] where c I is the phase boundary concentration between isotropic and biphasic regions and c A is that between biphasic and anisotropic regions.…”

“…Reproduced with permission from refs. [65] and [48]. Copyright 2019 and 2021, American Chemical Society.…”

“…On the contrary, all the solutions including linear and ring polymers have similar sharp peaks in the higher q region from 3 to 10 nm −1 . According to our recent paper, [ 48 ] these peaks can be assigned as hexagonally (unfilled circles) and tetragonally (filled squares) packed cylinders. If we consider that the linear ATBC aligns parallel in the concentrated solutions, the current diffraction results indicate the ring polymers should have pseudo rodlike conformation in the high concentrated solutions.…”

“…b) The ratio of the L K values for ring and linear are plotted against (L/L k ) linear . Reproduced with permission of ref [48]…”