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Molecular weight distributions for polydisperse systems

1959; Wiley; Volume: 38; Issue: 134 Linguagem: Inglês

10.1002/pol.1959.1203813406

1542-6238

Verne N. Schumaker,

Phase Equilibria and Thermodynamics

Abstract In this communication, equations are developed which allow the calculation of well defined average molecular weights and molecular weight distributions for unfractionated polydisperse polymer systems by appropriate combinations of the results of sedimentation, viscosity, and diffusion measurements. This theoretical approach is based upon the existence, for the polymer‐solvent system being studied, of a simple equation relating molecular weight to sedimentation coefficient. The particular equation chosen in this communication is the relation M = AS γ where M and S are the molecular weight and the sedimentation coefficient, respectively, and A and γ are constants for polymer‐solvent system being studied. The equations developed show how the constants A and γ may be determined from measurement of other hydrodynamic properties such as the diffusion coefficient and the intrinsic viscosity of the unfractionated system. Systems which are homogeneous with respect to molecular weight but polydisperse in shape are also considered, and equations are developed for determining the molecular weight of such preparations. Finally, systems polydisperse both with respect to shape and molecular weight are examined, and a possible method for the molecular weight characterization of such systems is presented.