Comparative Study of SEC and AF4 in the Characterization of Organic Soluble Synthetic Polymers

Abstract

Synthetic polymers used in various technical applications were analyzed by asymmetric flow field flow fractionation (AF4) and size exclusion chromatography size exclusion without dash is more frequent (SEC) followed by a multi-angle light scattering (MALS) photometer and the results were compared from the view point of the resolution of the two methods and their ability to determine the molar mass distribution. The analyzed polymers covered broad molar mass range and included linear, randomly branched and star-shaped molecular topologies. Narrow polystyrene standards were used to determine the molar mass dependence of the efficiency. The number-average molar masses obtained by SEC-MALS were systematically lower compared to those from AF4-MALS with the exception of highly branched polymers, whereas the weight-averages and z-averages were well consistent except for polymers containing ultra-high molar mass fractions undergoing shear degradation in SEC columns. The number of theoretical plates in AF4 was molar mass-dependent as predicted by the theory. Using linear cross flow decay, the molar mass dependence of the AF4 selectivity showed an arc-shaped pattern. The AF4 mass recovery was close to 100% for all samples not containing molecules below the cut-off of the channel membrane.