A Comparative Study of Xanthans by Light Scattering
Xanthan samples from four commercial manufacturers were studied in synthetic reservoir brines and a dilute NaCl solution. The samples included broth and powdered xanthan products. The weight-average molecular weight, Mw, for each sample was measured in the different solvents by low angle light scattering. Mw was not affected by the brine composition, and no evidence for increased aggregation in high-salinity, high-hardness brines was found. Mw varied from 4 × 106 g/mol to 12 × 106 g/mol. Variations in molecular weight were also observed among samples from one manufacturer. The translational diffusion coefficients of the xanthans could not be measured by a dynamic light scattering technique. Other modes of motion in addition to translational diffusion may have been detected at the 40° scattering angle as a direct result of the high polymer molecular weights.
KeywordsApparent Diffusion Coefficient Virial Coefficient Translational Diffusion Scattered Light Intensity Translational Diffusion Coefficient
Unable to display preview. Download preview PDF.
- 6.In retrospect, this procedure of dispersing the powdered Xanthan D in distilled water may have affected the Mw compared to direct dispersal into brine.Google Scholar
- 8.Tanford, C., “Physical Chemistry of Macromolecules”, Wiley, New York (1961).Google Scholar
- 9.Chauveteau, G, Kohler, N., Soc. Pet. Eng. J., 361–368, June 1984.Google Scholar
- 10.Ford Jr., N. C., in “Dynamic Light Scattering”, Pecora, R., Ed., Plenum, New York (1985) pp. 7–57 andGoogle Scholar
- Weiner, B., in “Modern Methods of Particle Size Distribution Analysis”, Barth, H., Ed., Wiley, New York (1984) pp. 93–116.Google Scholar
- 15.Holzwarth, G. Dev. Ind. Microbiol., 26, 271–280 (1985).Google Scholar
- 18.Pecora, R., in “Scattering Techniques Applied to Supramolecular and Nonequilibrium Systems”, Chen, S. H., Chu, B., and Nossal, R., Ed., Plenum, New York (1980) pp. 161–172.Google Scholar