SALT EFFECT ON SIZE-EXCLUSION CHROMATOGRAPHY OF PARTIALLY SULFONATED ALTERNATING COPOLYMERS OF MALEIC-ACID AND STYRENE IN A POLAR-SOLVENT

The molecular mass distributions of poly[(maleic acid)-alt-styrene] (S MA) and poly[(maleic acid)-alt-(p-sulfostyrene, styrene)] (SSMA) were measured by size-exclusion chromatography (SEC) in N,N-dimethylformami de (DMF) and in DMF containing different amounts of LiBr. The degree o f sulfonation of SSMA varies from 18.3 mol% (SSMA I), to 44.8 mol% (SS MA II) and to 83 mol% (SSMA III). Measurements were made at 40 degrees C using a mu Bondagel set of columns. SEC measurements were followed by viscosity measurements at 25 degrees C in the same media and by lig ht scattering measurements only far the SSMA I sample. The concentrati ons of LiBr added to DMF were 0.025, 0.075 and 0.10 M, at which concen trations of counter ions the viscosity effect of polyelectrolyte was s uppressed in all samples. The addition of LiBr to DMF shifted the chro matograms towards longer elution volumes (lower molecular mass); howev er, this shift was not significant in the case of the SSMA III sample, although the concentration of LiBr was 0.1 M. With the highest concen tration of LiBr there was a problem with solubility of the sample. The M(W) values vary from 24.1 . 10(6) (SSMA III in DMF) to 5.7 . 10(4) ( SSMA I in DMF-0.10 M LiBr). Light-scattering data showed that SEC meas urements using the polystyrene calibration graph afford only relative values for the molecular mass distribution.