Solution Properties of Amylose Tris(3,5-dimethylphenylcarbamate) and Amylose Tris(phenylcarbamate): Side Group and Solvent Dependent Chain Stiffness in Methyl Acetate, 2-Butanone, and 4-Methyl-2-pentanone

Abstract

Five amylose tris(3,5-dimethylphenylcarbamate) (ADMPC) samples ranging in weightaverage molecular weight Mw from 1.7  10 4 to 3.4  10 5 were studied by light and small-angle X-ray scattering, sedimentation equilibrium, and viscometry in methyl acetate (MEA), 2-butanone (MEK), and 4-methyl-2-pentanone (MIBK) at 25 °C. Seven amylose tris(phenylcarbamate) (ATPC) samples whose Mw ranges between 2  10 4 and 3  10 6 were also investigated in MEK at 25 °C. The radii of gyration, particle scattering functions, and intrinsic viscosities determined as a function of Mw were analyzed in terms of the cylindrical wormlike chain model mainly to determine the Kuhn segment length  -1 and the contour length h (or the helix pitch) per residue. While the obtained h values (0.36 -0.38 nm) of ADMPC are quite insensitive to the solvents, the  -1 value is not only 1.5 -3 times larger than that of ATPC in the corresponding solvent, but also significantly increases with an increase of the molar volume of the solvent and it reaches 73 nm in MIBK, which is the highest value for previously investigated phenylcarbamate derivatives of polysaccharides. This high stiffness is most likely due to the steric hindrance of the solvent molecules H-bonding with the NH groups of the polymer.

Solvent‐dependent conformation of a regioselective amylose carbamate: Amylose‐2‐acetyl‐3,6‐bis(phenylcarbamate)

“…The latter value is 12% smaller than that at the wavelength used for light scattering (436 nm). Similar wavelength dependence was also found for other polymer solvent systems22 including amylose carbamate derivatives 10, 11, 12, 16…”

“… Molar mass dependence of [η] M 0 for AAPC in DIOX (unfilled squares), MEK (unfilled circles), 2EE (unfilled triangles) along with our previous data10, 16 for ATPC in DIOX (filled squares), MEK (filled circles), and 2EE (filled triangles), all at 25°C. Solid curves, theoretical values for the wormlike cylinder model with the parameters listed in Table III.…”

“…The gyration radius 〈 S 2 〉 z from SAXS and 〈 S 2 〉 app from SLS were determined as initial slopes and the former values are summarized in Table I along with the intrinsic viscosities [η] and the average M w from different solvents. The molar mass dependence of [η] M 0 is displayed in Figure 3 along with those for ATPC in the corresponding solvents,10, 16 where M 0 denotes the molar mass of the repeat unit. The [η] M 0 data for the polymers in DIOX are almost equivalent in the investigated range of molar mass, indicating the almost the same main‐chain conformation.…”

“…The obtained λ −1 in each solvent is fairly consistent with that from P ( q ) whereas the d value from [η] is much larger than those from P ( q ). This inconsistency is well known for amylose carbamates10, 11, 12, 16, 32, 33 as well as for the other polymers5, 34, 35 because the d value from [η] reflects the hydrodynamic friction while that from P ( q ) is determined from the electron density profile including side groups and solvent molecules around the chain contour.…”

“…Vertically polarized incident light of 436 nm wavelength was used and the reduced scattering intensities R θ , Hv and R θ , Uv was measured with or without analyzer in the horizontal direction, respectively, in a scattering angle θ ranging from 22.5° to 150°. Optically anisotropic effects were not negligible for AAPC50K, AAPC100K, and AAPC200K as is the case of amylose tris(3,5‐dimethylphenylcarbamate) (ADMPC)16 and cellulose tris(3,5‐dimethylphenylcarbamate) (CDMPC) 17. Indeed, the optical anisotropy factor δ was at most 1.00 × 10 −2 , which causes 7% error to M w from R θ , UV .…”