The newer coatings technologies of waterborne, high solids, powder, and radiation curable coatings generally require high molecular weight latex polymers or strategically designed low molecular weight polymers, oligomers, and reactive additives. The design of these resin materials requires molecular weight distribution (MWD) information in the very high and very low molecular weight ranges which are accessible by size exclusion chromatography (SEC). In addition, there is a need for compositional distribution information as a function of molecular weight, particularly for oligomers; absolute MWD information, particularly for water-soluble polymers; and chain-branching information for high molecular weight polymers.
In this paper, the SEC separation mechanism, molecular weight calibration methods including the use of hydrodynamic volume, data treatment methods, and polymer chain-branching determination will be discussed. The use of molecular size sensitive detectors (viscometer, light scattering) and compositional sensitive detectors (UV-visible, IR) will be discussed in the context of illustrative qualitative and quantitative examples. The practice of high resolution SEC analysis of oligomers will be discussed and illustrated with problem-solving examples.