Thermal Field-Flow Fractionation

Separation techniques that fall under the general category of field-flow fractionation (FFF) have been around for almost 30 years. This article focuses on the FFF subtechnique most applicable to the separation and characterization of industrial polymers, namely thermal FFF (ThFFF). The past and future growth of ThFFF are discussed in relation to size-exclusion chromatography (SEC). In reviewing applications, the complementary nature of the two techniques becomes apparent. In contrast to SEC, which excels in the lower molecular weight range, ThFFF has clear advantages above 10⁵ g-mol^-1, and its range extends through the colloidal size domain. Furthermore, the strong dependence of retention on chemical composition in ThFFF is exploited in the analysis of copolymers and surface-modified colloids. When combined with SEC and viscometry or light scattering, the compositional selectivity of ThFFF adds an extra dimension to the analysis of complex mixtures of polymeric materials.