In a recent application note, we outline the pulsed field gradient spin echo diffusion technique as an alternative to SEC. This method has a simplified sample preparation, less solvent consumption, and can be less time consuming.
The molecular weight distribution (MWD) and the polydispersity index (PDI) are important numbers for characterizing polymers. They reflect the type of polymerization reaction and thus are related to the physical and mechanical properties of polymer mixtures. Currently size exclusion chromatography (SEC), also known as gel permeation chromatography, is one of the most common methods used to directly determine MWD based on the hydrodynamic volume of the dissolved polymer. However, SEC measurements require special sample preparation and a large amount of solvent, and they are time consuming. Such drawbacks can be avoided by an NMR method using the pulsed field gradient spin echo diffusion technique (PFG- or PGSE-diffusion) as an alternative method to SEC.