LAUSR

Macroporous, monodisperse PS/DVB particles with diameters of 4.0-4.6 μm were functionalized via free radical graft polymerization to create high performance anion exchangers. Varying the amount of monomer from 0 to 10 mmol per 2.0 g PS/DVB allows a control of the column capacity to create columns with capacities up to 350 μeq/column for 100 mm columns. No further increase of the capacity is observed when using more than 6 mmol of the monomer due to a rivaling homopolymerization. With increasing capacity, the exchangers showed increasing selectivity factors of Br- and NO3- in reference to Cl- from 2.4 to 4.3 and 3.5 to 4.6, changing the elution order in the process. At the same time, contradicting the retention model, the selectivity of SO42- did not change with increasing capacity. Analyzing the amount of converted double bonds during functionalization allowed to identify a grafting-onto mechanism, as the amount of converted double bonds ranges from 0% to 52% depending on the amount of monomer used. This information also allowed the calculation of the average chain length, which ranges from 1 to 6 exchanger groups. The average chain length depends on the amount of monomer used, creating higher average chain lengths with higher amounts of monomer. However, it was not possible to link the observed selectivity differences to the average chain lengths of the columns or the influence of the column capacity on the ion exchange mechanism.