Solution Properties of a Cyclic Chain Having Tunable Chain Stiffness: Cyclic Amylose Tris(<i>n</i>‑butylcarbamate) in Θ and Good Solvents

Small-angle X-ray scattering measurements were made for nine cyclic amylose tris­(<i>n</i>-butylcarbamate) (cATBC) samples ranging in the weight-average molar mass <i>M</i>_w from 1.6 × 10⁴ to 1.1 × 10⁵ to determine the <i>z</i>-average mean-square radius of gyration ⟨<i>S</i>²⟩_<i>z</i> and the particle scattering function <i>P</i>(<i>q</i>) in two good solvents, tetrahydrofuran (THF) and methanol (MeOH) at 25 °C and in a Θ solvent, 2-propanol (2PrOH) at the Θ temperature (35 °C). Static and dynamic light scattering measurements were carried out for cATBC in 2PrOH to determine <i>M</i>_w, the second virial coefficient <i>A</i>₂, and the hydrodynamic radius <i>R</i>_H. The dimensional and hydrodynamic properties are consistently explained by the current theories for wormlike ring having substantially the same model parameters obtained for linear analogues, that is, the Kuhn segment length λ^–1 of THF, 2PrOH, and MeOH are 75, 20, and 11 nm, respectively. Furthermore, number of hydrogen bonds decreases with the order of THF, 2PrOH, and MeOH, as is the case with linear ATBC. These results indicate that cATBC has rigid helical backbone stabilized by intramolecular hydrogen bonds in THF and it loosens with increasing solvent polarity. Indeed, lyotropic liquid crystallinity was found for cATBC in THF. In the Θ condition, 2PrOH at 35 °C, cATBC has large positive <i>A</i>₂ values, (1.3–1.4) × 10^–4 mol g^–2 cm³. It is successfully explained by the simulation results considering intermolecular topological interaction