Concentration Effects in Sec for Polymer/Polymer/Solvent Systems

A model quantitatively describing the experimental shifts in elution volumes of polymeric solute A in the presence of another polymer B is developed. The concentration-dependent shrinkage of A coils has been evaluated from the intrinsic viscosity displayed by polymer A in the ternary solution formed by itself at cA concentration + polymer B at cB concentration + solvent. Resulting concentration effects depend on both polymer concentrations (cA and cB), on the intrinsic viscosities of both polymers in the solvent (|η|A and |η|B), on the Huggins' coefficients kA and kB, and on the quadratic concentration coefficients in the polynomial expansion of ηsp/c, namely k′ A and k′ B. Predicted elution volumes are compared with experimental ones for two different types of literature systems: those studying polymer A elution at diverse cA concentrations in eluents consisting of mixtures of polymer B + solvent and those in which polymer A + polymer B mixtures are injected at once in the pure solvent used as eluent. In order to eliminate experimental uncertainties about ki and k′ i (i=A, B) values, applied k′ i values were those obtained from the empirical correlation k′ i + 0.122 = ki 2 whereas ki ones were obtained from Imai's equation.