Determination of the chemical composition distribution of copolymers of styrene and butadiene by gradient polymer elution chromatography

In order to determine the chemical composition distribution (CCD) of styrene-butadiene copolymers, gradient polymer elution chromatography has been performed. The separation is mainly based on differences in solubility among the copolymer molecules with different chemical composition. The solubility of a copolymer is dependent on the following parameters: temperature, type of solvent/non-solvent mixture, molecular mass of the polymer and the chemical composition of the polymer. The resolution of the gradient polymer elution chromatographic separation and the molecular mass dependency are influenced by the solvent/non-solvent combination. In order to obtain a reliable separation according to chemical composition, the differences in solubility must be sufficiently high and the molecular mass dependence must be negligible. In order to separate styrene-butadiene copolymers, synthesized by emulsion polymerization, a tetrahydrofuran-acetonitrile gradient was used. After calibration of the chromatographic system with styrene-butadiene copolymer standards, the CCD of styrene-butadiene copolymers could be calculated.