[摘要]：Twelve amylose tris(n-butylcarbamate) (ATBC) samples ranging in weight-average molecular weight from 1.7 x 10(4) to 1.7 x 10(6) have been prepared and studied by light and small-angle X-ray scattering, sedimentation equilibrium, viscosity, infrared absorption (IR), and optical rotation in methanol (MeOH), tetrahydrofuran (THF), and their mixtures at 25 degrees C(or 20-25 degrees C for IR). Data for mean-square radius of gyration, the particle scattering function, and the intrinsic viscosity are analyzed on the basis of the wormlike chain to yield h (contour length per residue) = 0.32 nm and lambda(-1) (Kuhn's segment length)= 11 nm in MeOH and h = 0.26 nm and lambda(-1) = 75 nm in THF. The high stiffness in THF indicated by lambda(-1) = 75 nm is most likely due to the intramolecular hydrogen bonding (between C=O and NH groups of ATBC observed its the splitting amide 1 band in the IR spectra. Furthermore, the h value in this solvent is considerably smaller than the helix pitches per residue of 0.37-0.40 nm for amylose triesters in the crystalline state and those of 0.32-0.42 nm for semiflexible amylose tris(phenylcarbamate) in various solvents (lambda(-1) = 15-24 nm), indicating that the ATBC chain forms a lightly wound helix in THF. As the number of intramolecular hydrogen bonds decreases, i.e., its the MeOH content increases in THF-MeOH mixed solvents lambda(-1) decreases while h increases. These relationships are successfully explained by a two-state model in which each chain consists of randomly distributed semiflexible (loosely helical),and rodlike (rigid helical) sequences. The resultant h Values for the rodlike and semiflexible portions are 0.25-0.26 and 0.32 nm, respectively.
