𝔖 Bobbio Scriptorium
✦   LIBER   ✦

Molecular weight distribution by velocity ultracentrifugation

✍ Scribed by Wales, M. ;Rehfeld, S. J.

Book ID
104532368
Publisher
John Wiley and Sons
Year
1962
Weight
637 KB
Volume
62
Category
Article
ISSN
0022-3832

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✦ Synopsis

Abstract

A method is outlined for the determination of molecular weights and molecular weight distributions in linear, neutral polymers from boundary spreading data obtained from the ultracentrifuge. By use of the intrinsic viscosity, and having knowledge of its molecular weight dependence, it is possible to avoid calibration of the method with fractions of known molecular weight. Because of a maximum sensitivity of sedimentation coefficient to molecular weight, and only small concentration dependence of the sedimentation coefficient, theta solvents are preferred for these measurements. Corrections are made for pressure dependence of the sedimentation rate. The method is illustrated by measurements on polystyrenes in cyclohexane at 34Β°C. Comparison is made with precipitation chromatography data. Because of the number of experiments which must be made in order to extrapolate data to infinite dilution (each experiment consisting of at least four schlieren diagrams) this type of analysis probably involves as much labor as precipitation chromatography.

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