Absolute intensities $\Delta i\left(q\right)\mathrm{}$ of small-angle x-ray scattering (SAXS) and ultra-small-angle x-ray scattering (USAXS) were measured in a wide range of scattering vector q from $2\times {10}^{-4}$ to 0.5 ${\mathrm{\AA }}^{\mathrm{-}1}$ for transparent (VI-P) and translucent (VI-L) cellulose hydrogels prepared by coagulation and regeneration of viscose in acid solutions with and without acetone, respectively. We obtained the scattering intensities at very small q conveniently by desmearing the combined data measured by SAXS and USAXS. The plot of $\Delta {i\left(q\right)q}^2$ versus ${\log }_{10}q$ showed a peak at $-2.5<\mathrm{}{\log }_{10}q<\mathrm{}-\mathrm{1.0.}$ By assuming a two-phase model with the high-density phase (phase 1) composed of only cellulose and with the low-density phase (phase 2) composed of cellulose dispersed in water, volume fractions of phase 1 in VI-P and VI-L were determined to be 0.18 and 0.09, respectively, from the mean-square fluctuation of electron density determined as $\int \Delta {i\left(q\right)q}^2\mathrm{dq}.\mathrm{}$ By fitting the observed scattering profile with the theoretical particle scattering functions of spheres, the average diameter of the high-density region including crystallite was determined to be 120 Å for VI-P and 80 Å for VI-L. Similar analyses were applied also to freeze-dried VI-P. These results were consistent with those obtained by the wide-angle x-ray-diffraction measurement and also with the observation by scanning probe microscopy.

• Received 29 September 1999

DOI:https://doi.org/10.1103/PhysRevE.62.727