Abstract
The limitations of traditional gas adsorption models for describing water vapor sorption by amorphous pharmaceutical solids are described and an alternative approach based on polymer solution theories is proposed. The approach is tested by comparing a priori predicted isotherms with literature data for the poly(vinylpyrrolidone)(PVP)–water system. The well-known Flory– Huggins model is able to describe the water vapor sorption isotherm only when the PVP–water mixture is in the rubbery state (i.e., above its glass transition temperature). However, a newer model developed by Vrentas and co-workers, which takes into account the plasticizing effect of water on the polymer, is able to describe the entire form of the isotherm. Consideration of the parameters in this model allows a number of critical variables to be identified and also enables the characteristic shape of the water vapor sorption isotherm to be explained.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
REFERENCES
J. Callahan, G. Cleary, M. Elefant, G. Kaplan, T. Kensler, and R. Nash. Equilibrium moisture content of pharmaceutical excipients. Drug. Dev. Indust. Pharm. 8:355–369 (1982).
C. Ahlneck and G. Zografi. The molecular basis of moisture effects on the physical and chemical stability of drugs in the solid state. Int. J. Pharm. 62:87–95 (1990).
P. C. Hiemenz. Principles of Colloid and Surface Chemistry, Marcel Dekker, New York, 1986.
S. Brunauer, P. H. Emmett, and E. Teller. Adsorption of gases in multimolecular layers. J. Am. Chem. Soc. 60:309–319 (1938).
G. Zografi. States of water associated with solids. Drug Dev. Indust. Pharm. 14:1905–1926 (1988).
M. J. Kontny and C. A. Mulski. Gelatin capsule brittleness as a function of relative humidity at room temperature. Int. J. Pharm. 54:79–85 (1989).
G. W. Radebaugh, S. R. Babu, and J. N. Bondi. Characterisation of the viscoelastic properties of compacted pharmaceutical powders by a novel non-destructive technique. Int. J. Pharm. 57:95–105 (1989).
H. Levine and L. Slade. Glass transitions in foods. In H. G. Scwartzberg and R. W. Hartel (eds)., Physical Chemistry of Foods, Marcel Dekker, New York, 1992, pp. 83–219.
C. A. Oksanen. The Interaction of Water with Amorphous Solids, M.Sc. thesis, and Molecular Mobility in Mixtures of Absorbed Water and Solid Poly(vinylpyrrolidone), Ph.D. thesis, University of Wisconsin—Madison, 1989 and 1992.
C. A. Oksanen and G. Zografi. The relationship between the glass transition temperature and water vapor absorption by poly(vinylpyrrolidone). Pharm. Res. 7:654–657 (1990).
A. P. MacKenzie and D. H. Rasmussen. Interactions in the water-polyvinylpyrrolidone system at low temperatures. In H. H. G. Jellinek (ed.), Water Structure at the Water Polymer Interface, Plenum Press, New York, 1972, pp. 146–172.
P. J. Flory. Principles of Polymer Chemistry, Cornell University Press, New York, 1953.
J. Brandrup and E. H. Immergut (eds.). Polymer Handbook, Wiley, New York, 1975.
B. E. Eichinger and P. J. Flory. Thermodynamics of polymer solutions. Part 1. Natural rubber and benzene. Trans. Faraday Soc. 64:2035–2052 (1968).
M. A. Cohen Stuart. Flexible Polymers at a Solid-Liquid Interface: The Adsorption of Polyvinylpyrrolidone onto Silica, Ph.D. thesis, Wageningen University, Wageningen, The Netherlands, 1980.
J. S. Vrentas and J. L. Duda. Diffusion of small molecules in amorphous polymers. Macromolecules 9:785–790 (1976).
J. S. Vrentas and J. L. Duda. Diffusion in polymer-solvent systems. 1. Re-examination of the free volume theory. J. Polym. Sci. (Polym. Phys. Ed.) 15:403–416 (1977).
M. H. Cohen and D. Turnbull. Molecular transport in liquids and glasses. J. Chem. Phys. 31:1164–1169 (1959).
J. S. Vrentas, J. L. Duda, and H.-C. Ling. Antiplasticization and volumetric behaviour in glassy polymers. Macromolecules 21:1470–1475 (1988).
J. S. Vrentas and C. M. Vrentas. Volumetric behaviour of glassy polymer-penetrant systems. Macromolecules 22:2264–2266 (1989).
J. S. Vrentas and C. M. Vrentas. Predictions of volumetric behaviour for glassy polymer-penetrant systems. J. Polym. Sci. (Polym. Phys. Ed.) 28:241–244 (1990).
J. S. Vrentas and C. M. Vrentas. Sorption in glassy polymers. Macromolecules 24:2404–2412 (1991).
E. Filby and O. Maass. The volume relations of the system cellulose and water. Can. J. Res. 7:162–177 (1932).
D. T. Turner. Polymethylmethacrylate plus water: sorption kinetics and volumetric changes. Polymer 23:197–202 (1982).
M. Scandola, G. Ceccorulli, and M. Pizzoli. Water clusters in elastin. Int. J. Biol. Macromol. 3rd April: 147–149 (1981).
J. M. Pochan, C. L. Beatty, and D. F. Pochan. Different approach for the correlation of the Tg of mixed amorphous systems. Polymer 20:879–886 (1979).
T. S. Chow. Molecular interpretation of the glass transition temperature of polymer-diluent systems. Macromolecules 13:362–364 (1980).
F. Franks. Water solubility and sensitivity—hydration effects. In C. A. Finch (ed.), Chemistry and Technology of Water Soluble Polymers, Plenum Press, New York, 1981, pp. 157–178.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Hancock, B.C., Zografi, G. The Use of Solution Theories for Predicting Water Vapor Absorption by Amorphous Pharmaceutical Solids: A Test of the Flory–Huggins and Vrentas Models. Pharm Res 10, 1262–1267 (1993). https://doi.org/10.1023/A:1018901325842
Issue Date:
DOI: https://doi.org/10.1023/A:1018901325842