How to Maximize Absolute Molecular Weight Measurement Accuracy: Synthetic Polymers
Application Note Aug 19, 2015
Malvern Instruments Limited
In this application note, the molecular weight, molecular weight distribution and size of three common polymers are measured using the OMNISEC system.
The physical properties and behavior of polymers depends strongly on the properties of the polymer molecules themselves. Molecular weight and molecular weight distribution, molecular size and structure all affect how the material will behave. By understanding and controlling these properties, polymer manufacturers can control polymer production and quality. Historically, accurate measurement of polymer molecular weight has been dependent on having standards of the same polymer but the introduction of advanced detection techniques such as light scattering and intrinsic viscosity have made absolute measurements possible.
Malvern’s OMNISEC system is a completely new multi-detector GPC system that combines light scattering, refractive index (RI), ultraviolet (UV) and intrinsic viscosity (IV) detectors to generate a large amount of information about a sample simultaneously. Its new design means it is capable of making these measurements with less sample and lower molecular weights than ever before.
GPC/SEC (gel-permeation or size-exclusion chromatography) is the most commonly used tool for assessing these parameters. The principle of GPC involves separating the sample as it travels through a porous but inert column matrix. While smaller molecules penetrate the pores more deeply, larger molecules are excluded and thus travel through the column faster. The result is a separation based on hydrodynamic volume. However, in most cases, the desire is to know the molecular weight of the sample.