Theory of multiple-detection size-exclusion chromatography of complex branched polymers

SEC separates complex branched polymers by hydrodynamic volume, rather than by molecular weight or branching characteristics. Equations relating the response of different types of detectors are derived including band broadening, by defining a distribution function N'(M,V-h), the number of chains with molecular weight M and hydrodynamic volume V-h. While the true molecular weight distribution of complex polymers cannot be determined by SEC, irrespective of the detector used, the formalism enables multiple detection SEC data to be processed to both analyze the polymer sample and reveal mechanistic information about polymer synthesis. The formalism also shows how the true weight- and number-average molecular weight, (M) over bar (w) and (M) over bar (n), can be obtained from correct processing of the hydrodynamic volume distributions.