Small-angle scattering by polyelectrolyte solutions: Intermolecular correlation function of poly(methacrylic acid) in salt-free semidilute solutions

Intermolecular correlations in salt-free solutions of poly(methacrylic acid) neutralized by NaOD were investigated as a function of the degree of neutralization, α. At α = 0, the relative concentration of monomer units belonging to foreign macromolecules at a distance r from a reference monomer unit, g(r) = N(r) N ̄ , is nearly equal to unity in the r range investigated. Already at α = 0.01, however, the values of g( r) are significantly smaller than unity near the origin. With increasing r, g( r) monotonically increases and reaches unity at r = 120–150 A ̊ . No oscillations indicating an ordered structure are observed. The shape of g( r) curves is in agreement with the correlation hole concept. The non-monotonic dependence of the radius of the correlation hole on α is explained by the overlap of macroions at higher degrees of neutralization.