Synthesis and characterization of microporous polymer microspheres with strong cation-exchange character

In this paper the synthesis and characterization of microporous polymer microspheres with ultra-high specific surface areas (>1000 m2/g) and strong cation-exchange character is described. The microspheres were synthesized by the hypercrosslinking of swellable precursor particles which had been produced by precipitation polymerization. The strong cation-exchange character, arising from the presence of sulfonic acid groups, was introduced through post-hypercrosslinking chemical modification reactions. Two alkyl sulfate reagents of differing polarity were compared as reagents for the sulfonation reactions, and a synthetic methodology was devised that allowed the sulfonic acid content of the microspheres to be controlled. Following a series of small-scale optimization experiments, optimized conditions were applied on a larger scale to the synthesis of three distinct polymers (HXLPP-SCX) tailored for use as strong cation-exchange (SCX) sorbents in solid-phase extraction (SPE) studies. All three polymers were in the form of polymer microspheres (mean particle diameters 3-5 μm) with relatively narrow particle size distributions and specific surface areas up to 1370 m2/g, and had tuneable ion-exchange capacities (IECs) ranging from 1.7-2.8 mmol/g.