SCATTERING FROM MULTICOMPONENT POLYMER MIXTURES - WEAKLY CHARGED POLYMERS

The static scattering properties of weakly charged homopolymers and copolymers in solution are investigated by using the generalization of Zimm's equation to multicomponent polymer systems. The interaction matrix is modeled as a sum of the short-range excluded-volume matrix and the long-range Debye-Huckel matrix. Several cases are considered, depending on the charge distribution among species. If the species are charged equally, the scattering behavior is essentially controlled by the thermodynamic parameter-chi. If the species have opposite charges, the electrostatic attraction enhances significantly their compatibility. The case of a mixture of weakly charged and neutral polymers is also investigated, and the results are consistent with those reported by Joanny and Leibler. The description of counterions and salt ions is also discussed. It is argued that when these ions are considered as point particles, their role should be limited to the screening of electrostatic interactions and the electroneutrality condition.