Lyotropic Liquid Crystallinity of Amylose Tris(alkylcarbamates): Cholesteric and Smectic Phase Formation in Different Solvents

Abstract

Lyotropic liquid crystallinity was investigated for amylose tris(n-butylcarbamate) (ATBC), amylose tris(ethylcarabamate) (ATEC), and amylose tris(n-hexylcarbamate) (ATHC) in tetrahydrofuran (THF) and ethyl lactates (ELs) by using phase separation experiments, polarized microscopic observation, small-angle X-ray diffraction, and circular dichroism measurements. Concentrated THF solution of ATBC has selective reflection at visible light wavelength, indicating the formation of cholesteric phase. A current theory well explains the phase diagram of ATBC, ATEC, and ATHC in THF. On the other hand, ELs solution forms smectic phase and it has significantly different phase diagram, that is, the biphasic range is much wider than that in THF. In other words, highly concentrated smectic phase can be obtained from semidilute and rather low viscosity ELs solution. This is likely because amylose alkylcarbamate chains may have significant anisotropic intermolecular attractive interaction in between polymer chains in ELs or intermolecular interactions between the chain ends are much more different from those in THF.

Lyotropic Liquid Crystallinity of Linear and Cyclic Amylose Derivatives: Amylose Tris(n-octadecylcarbamate) in Tetrahydrofuran and 2-Octanone

“…This theory is applicable not only for rigid synthetic polymers but also polysaccharide derivatives. 12,23,24 The helix pitch h per residue defined by h = LM 0 /M w was used instead of L to calculate c I and c A as a function of M w . Assuming h and  −1 from dilute solution properties, 13 that is, h = 0.36 nm and  −1 = 45 nm in MHK and h = 0.40 nm and  −1 = 24 nm in THF, d and α are needed to calculate ΔA at fixed μ0, c, and T. The theoretical value can be evaluated as a solution of the following simultaneous equations with the osmotic pressure  and the chemical potential μ of the spherocylinder…”

“…2 Indeed, phase boundary concentrations for amylose alkylcarbamates tend to lower with increasing alkyl side chains from ethyl to hexyl groups in THF. 12 This suggests that linear and cyclic amylose tris(n-octadecylcarbamate)s (ATODC and cATODC) for which chemical structures are shown in Chart 1 are suitable to investigate their lyotropic liquid crystallinity since both ATODC and cATODC behave as stiff chains in solution. 13 We thus determined their phase boundary concentrations in 2-octanone (MHK) and THF.…”

Lyotropic Liquid Crystallinity of Linear and Star Poly(quinoxaline-2,3-diyl)s: Isotropic-Liquid Crystal Phase Equilibria in Tetrahydrofuran

“…The phase boundary concentration has therefore been widely investigated for many linear polymers as a function of the molar mass of the polymer. [10][11][12][13][14][15][16] Poly(quinoxaline-2,3-diyl)s are classified to as a helical polymer 17 of which internal rotation of the main chain is significantly restricted in solution and thus applied for various asymmetric reactions. [18][19][20] Indeed, a poly(quinoxaline-2,3-diyl), that is, poly [5,8-dimethyl-6,7bis(propoxymethyl)quinoxaline-2,3-diyl] (LPQ) behaves as a stiff chain of which the Kuhn segment length  −1 (or twice the persistence length) was estimated to be 43 nm in tetrahydrofuran (THF), which is a good solvent of LPQ.…”

Liquid Crystals of Cellulosics: Fascinating Ordered Structures for the Design of Functional Material Systems

“…They were prepared from enzymatically synthesized amylose with no branching. The three tris(alkylcarbamate)s assume a tightly wound helical conformation stabilized by intramolecular hydrogen bonds in THF [58] and have liquid crystallinity in the solvent [57]. The mesophase of ATBC in THF is a definite chiral nematic type, exhibiting selective reflection of visible light; the twist sense is left-handed and the absolute value of P increases with increasing temperature and decreasing concentration, as in the case of CtsPC/DMF lyotropics (Sect.…”

“…Actually, the lyotropic liquid crystallinity of amylose triphenylcarbamate (ATPC) would be difficult to investigate because of the extremely high viscosity of the concentrated solutions. Recently, Terao et al performed an interesting study [57] of lyotropic mesophase behavior of three amylose alkylcarbamates: amylose tris(ethylcarbamate) (ATEC), amylose tris(n-butylcarbamate) (ATBC), and amylose tris(n-hexylcarbamate) (ATHC). They were prepared from enzymatically synthesized amylose with no branching.…”