Retention behavior of copolymers in thermal field-flow fractionation and gel permeation chromatography

Retention behavior of polystyrene copolymers having different structures and compositions was investigated for measuring thermal diffusion coefficient (D-T) using thermal field-flow fractionation (ThFFF). Samples were random poly(styrene-co-methylmethacrylate)s, poly(styrene-co-isoprene) block copolymers having molecular weights ranging from 10(4) to 10(5). It was found that the ThFFF retention of copolymers is related to the composition as well as the molecular size of copolymers. For random copolymers D-T was a linear function of the monomer composition, and it was possible to determine the molecular weight of polymers by use of calibration curve of log(wt % M[eta]) versus log(D/D-T). For block copolymers, D-T values of diblock copolymers were greater than those of triblock. It was found that the thermal diffusion varies with the copolymer structure as well as the composition.