Matija Tomšič, Marija Bešter Rogač and Andrej Jamnik
Faculty of Chemistry and Chemical Technology, University of Ljubljana,
Aškerčeva 5, 1000 Ljubljana, Slovenia.
Small-angle X-ray scattering (SAXS) technique has been used to study so-
lutions of salts of poly(styrenesulphonic) acid containing lithium, strontium,
and a mixture of lithium an strontium counterions. Repulsive electrostatic
interactions between the polyions lead to a decrease of scattering intensity at
small values of the scattering vector q followed by a more or less pronounced
interaction peak. The position of the maximum varies with polyion concen-
tration and is strongly aected by the counterion charge. Addition of simple
electrolyte to the solution causes an increase of the forward scattering; at suf-
cient concentration of added salt the peak vanishes and the behavior of the
system becomes similar to the solution of neutral polymer.