Viscosity of Polymer Solutions and Molecular Weight Characterization

Since the pioneering research by Staudinger on dilutesolutionviscosity and its relation to the polymer molecular weight, viscosityanalysis has become a valuable technique for polymer characterization.The conventional approach is based on the Huggins approximation ofthe solution-specific viscosity by a quadratic function of concentration, c. We show how to reformulate this approach in a universalform by representing a solution-specific viscosity, eta(sp), as a generalized universal function eta(sp)(c) = alpha(c/c*) + (1 - alpha)(c/c*)(2) of chain overlap concentration, c*, determined at eta(sp) = 1, with numericalcoefficients alpha = 0.745 +/- 0.005 for good and 0.625 +/- 0.008 for a theta solvent. This viscosity representation can beviewed as a calibration curve for molecular weight determination froma measurement of the solution viscosity at a given solution concentration.Furthermore, the molecular weight dependence of the overlap concentrationprovides a means for quantifying the polymer/solvent affinity andthe solvent effect on chain flexibility. The extension of the approachto semidilute solutions opens a path for obtaining molecular weightin a broad concentration range without requiring a dilution and monitoringits change during the polymerization reaction from solution viscosity.

Automated summary

Viscosity analysis is a valuable technique for polymer characterization. This study proposes a new method to determine the molecular weight of polymers by representing the solution-specific viscosity as a generalized universal function of chain overlap concentration.