Gel permeation chromatography of poly(styrene-co-divinylbenzene) microgels. Effect of electrolyte concentration in the solvent system dimethylformamide plus lithium bromide

Tightly crosslinked poly(styrene-co-divinylbenzene) microgels with molecular weights in the range 10⁷-10⁸gmol^?1 have been dissolved in dimethylformamide containing LiBr and investigated by gel permeation chromatography and viscometry. The effect of LiBr concentration on the elution volume in GPC can be explained in terms of a diffuse double layer. The product [η]M adequately describes the separation in GPC provided that the LiBr concentration is high and adsorption is absent.