Osmotic Pressure and Polymer Molecular Weight Determination

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JCE Data-Driven Exercises

Osmotic Pressure and Polymer Molecular Weight Determination by W. Tandy Grubbs, Department of Chemistry, Stetson University, DeLand, FL 32720; [email protected] Keywords: Upper-Division Undergraduate, Physical Chemistry, Polymer Chemistry, Inquiry-Based/Discovery Learning, Solutions/Solvents, Physical Properties

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W. Tandy Grubbs Stetson University DeLand, FL 32720

A Web-accessible exercise is presented in which upperdivision undergraduate students can explore the method of determining polymer molecular weight from osmotic pressure measurements. The data were obtained from W. R. Krigbaum and L. H. Sperling ( J. Phys. Chem. 1960, 64, 99) and correspond to the osmotic pressure of cellulose tricaproate at four different concentrations and at three different temperatures in the solvent dimethylformamide. In addition to the polymer’s molecular weight, students are guided to determine the second virial coefficient and the Flory θ temperature for this system. This exercise is appropriate for use in a physical chemistry or polymer chemistry class.

Journal of Chemical Education  •  Vol. 86  No. 6  June 2009  •  www.JCE.DivCHED.org  •  © Division of Chemical Education