X‐ray scattering studies of the structure of aqueous hydroxy‐propylcellulose solutions

X‐ray diffraction studies have been undertaken on aqueous solutions of hydroxy propylcellulose (HPC) over a wide range of the scattering vector Q. The experiments revealed only modest differences in local structure on a distance scale ca. 5–300 Å despite the fact that they covered concentrations generally interpreted as ranging from the isotropic (35.1 wt %) to the anisotropic liquid crystalline (LC) phase (53.5 wt %). Several models were used to interpret the small‐angle scattering data, and each gave similar structural parameters and extrapolated intensities (Q → 0) for both solutions. Peaks were observed with d‐spacings ca. 12–17 Å in both materials. Wide‐angle x‐ray scattering (WAXS) showed slightly increased local order over a size range ca. 5–20 Å for the anisotropic solution, and this is consistent with a greater intensity of the 13 Å peak in this material. It is difficult to reconcile these findings with an interpretation of the LC state involving major differences with the isotropic phase and a high degree of orientational order extending over long length scales.