STRUCTURE AND CHARGE-DISTRIBUTION IN POLY(STYRENESULFONATE) ION-EXCHANGE RESINS

Poly(styrenesulfonate) ion exchange resins were investigated with smal l angle neutron scattering. The polymer, polymer counterion, and count erion partial structure functions and charge structure function were o btained with contrast matching in water. In the reciprocal space inter val q < 1 nm(-1), all partial structure functions display an upturn. T his is attributed to different swelling ofregions with differences in cross-link concentration, resulting in similar long range static heter ogeneity in polymer and small ion density. The charge structure functi on was found to satisfy the sum rules and demonstrates the strong supp ression oflarge scale temporal fluctuations. At larger wave vectors, t he structure functions reflect the distribution of counterions with re spect to the polymer charges. An effective charge screening length is obtained, and its value agrees with a strong association of the ionic species.