STUDIES IN THE THERMAL-DIFFUSION OF COPOLYMERS USING FIELD-FLOW FRACTIONATION

Earlier studies of copolymer thermal diffusion are extended here to in clude several new random and block copolymers of polystyrene and polyi soprene. Thermal diffusion coefficients for these polymers in tetrahyd rofuran and cyclohexane were obtained by thermal field-flow fractionat ion (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 c oefficient D(T) is a linear function of copolymer composition. This re lationship provides a basis for obtaining compositional information on such copolymers by ThFFF. For copolymers subject to radial segregatio n of their monomeric units, the significance of a given unit's role in thermal diffusion increases with the radial distance of the unit from the core of the solvated molecule. The dependence of retention on the radial distribution of monomeric units provides a basis for evaluatin g bonding arrangements in copolymers.