Linear and cyclic amylose derivatives having brush like side groups in solution: Amylose tris(n-octadecylcarbamate)s

Abstract

Seven linear amylose tris(n-octadecylcarbamate) (ATODC) samples ranging in the weightaverage molar mass Mw from 2.4  10 4 to 1.5  10 6 g mol −1 and their seven cyclic analogues (cATODC) of which Mw are from 3.6  10 4 to 1.9  10 5 g mol −1 were prepared to characterize their conformation in tetrahydrohuran (THF), in 2-octanone (MHK), and in tertbutyl methyl ether (MTBE). Light and small-angle X-ray scattering and viscosity measurements in dilute solution were employed to determine the particle scattering function P(q), the z-average mean-square radius of gyration S 2 z, and the intrinsic viscosity []. The obtained data were analyzed in terms of the wormlike chain model to determine the helix pitch per residue h and the Kuhn segment length  −1 which is a measure of the chain stiffness and equal to twice the persistence length. The parameters indicate that the linear ATODC has an appreciably extended local helical structure and high chain stiffness while the latter parameter  −1 in THF is lower than those for amylose alkylcarbamates with shorter side chains. This is most likely due to the repulsion between relatively long side groups. This chain extension and less stiff main chain were more significantly observed for the cyclic chains. Lyotropic liquid crystallinity in concentrated solutions supports the high rigidity of ATODC and cATODC chains in solution.

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

“…This value is consistent with the chain diameter of 3.2 nm estimated by the SAXS profile in dilute solution. 13 A similar broad peak was also found for concentrated MHK and THF solutions of ATODC and cATODC at somewhat lower q range. The actual q value at the peak slightly depends on the sample and concentration, that is, q = 1.6 -1.7 nm −1 for ATODC in MHK (0.31 < c / g mL −1 < 0.40), q = 1.6 -1.8 nm −1 for ATODC in THF (0.25 < c / g mL −1 < 0.40), q = 1.6 -1.8 nm −1 for cATODC in MHK (0.45 < c / g mL −1 < 0.70), and q = 1.7 -2.1 nm −1 for cATODC in THF (0.45 < c / g mL −1 < 0.50); note that the concentration were not very accurate because it was hard to prepare uniform solution in the capillary cell.…”

“…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…”

“…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. Smallangle X-ray scattering (SAXS) measurement was also carried out for bulk and concentrated ATODC and cATODC solutions to determine the local alignment of polymer chains in the liquid crystalline phase since they may also have thermotropic liquid crystallinity as in the case of polysaccharide derivatives with alkyl side groups.…”

Single-chain conformation of carboxylated schizophyllan, a triple helical polysaccharide, in dilute alkaline aqueous solution

“…Such a small h value was also found for curdlan (h = 0.18 nm) in 300 mM aqueous NaOH [33] while much larger value (h = 0.38 nm) was reported from the crystal structure of the single chain curdlan [34]. According to our recent research, tightly winding helical structure with relatively short h value can be stabilized for amylose derivatives when the side groups fit inside the helical main chain [35][36][37][38]. The shrunken helical structure for SPG and sclerox is thus most likely due to this specific interaction between the main chain and the side group as well as the intrinsic helical nature of -1,3-glucan.…”

A Temperature Responsive Polysaccharide Derivative in Aqueous Solution: Amylose Ethyl Carbamates

“…The chemical structure of the purified samples was confirmed by 1 H-NMR in deuterated dimethyl sulfoxide with a small amount of (trimethylsilyl)-1-propanesulfonic acid sodium salt (Figure S1) whereas the intensity of each peak cannot be estimated properly as in the case of our previous study for fully substituted derivatives. [27][28] The degree of substitution DS for which full substitution is defined as DS = 3 was determined from the weight ratio of carbon to nitrogen atoms which were determined by ultimate analysis. In the present study, we chose the conventional method to obtain AEC while a modern procedure without hazardous reagents 29 could be applicable to synthesize low DS samples.…”