Studies in the Thermal Diffusion of Copolymers Using Field-Flow Fractionation
Earlier studies of copolymer thermal diffusion are extended here to include several new random and block copolymers of polystyrene and polyisoprene. Thermal diffusion coefficients for these polymers in tetrahydrofuran and cyclohexane were obtained by thermal field-flow fractionation (ThFFF). The results confirm the dependence of thermal diffusion (and therefore ThFFF retention) on the radial distribution of monomeric units in the solvated macromolecule. For random copolymers and block copolymers that assume a random configuration, the thermal diffusion coefficient DT is a linear function of copolymer composition. This relationship provides a basis for obtaining compositional information on such copolymers by ThFFF.