Varying the porous structure of polystyrene/divinylbenzene beads prepared by Ugelstads activated swelling technique and examining its reversed phase HPLC properties

Monodisperse unfunctionalized polystyrene/divinylbenzene beads were prepared via Ugelstads two-step activated swelling procedure. The modification of the porous structure was achieved in two different ways, by either changing the kind and amount of diluent or the concentration of crosslinker. Overall 10 different types of diluents, both solvent and nonsolvent types, were utilized. In all cases divinylbenzene was used as crosslinking agent in concentrations of 55% and 80%, which are commercially available, and 100%, which had to be synthesized. The size and morphology of these particles were examined with scanning electron microscopy. For the analysis of the internal porous structure inverse size exclusion chromatography was conducted. Depending on the monomer and diluent composition beads in the range of 3.4-4.5 μm having a specific surface area from 90 to 1898 m2/g were synthesized. Separation performance was then also investigated using RP-HPLC with benzene and propylbenzene as analytes. Porous and reversed-phase properties were subsequently linked to explain the observed shift in retention and efficiency. Polymers having the highest specific surface area and the smallest mean pore diameter exhibited the best performance with reduced plate height of 3.1.