On the Accuracy of Molecular Weight and Radius of Gyration Measured by Right-Angle Light Scattering with SEC-Viscometry

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Abstract
The use of a right-angle light scattering detector with a size exclusion chromatograph equipped with an online viscometer provides a convenient method of estimating polymer molecular weight distribution. The 90° scattered intensity provides an initial estimate of the molecular weight at each elution slice. This value is then improved using an estimate of the light-scattering asymmetry based on the measured intrinsic viscosity in order to determine the 0° scattering intensity required to obtain the true molecular weight. In addition, an estimate of the radius of gyration can be obtained. In this paper the accuracy of the method is examined for different linear polymers and also for branched polymers. In most cases molecular weights within 2% of the true values can be obtained up to 1 × 106 g/mol. Errors are about 5% for molecular weights of 2 × 106 g/mol and rapidly increase for higher molecular weights. The errors in the radius of gyration estimated using this method are higher (∼ 10%); however, the viscometric radius is determined with high accuracy.