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The configuration of sodium poly(styrene sulfonate) at polystyrene/solution interfaces

1986; Elsevier BV; Volume: 111; Issue: 2 Linguagem: Inglês

10.1016/0021-9797(86)90044-5

1095-7103

Terence Cosgrove, T.M Obey, B. Vincent,

Material Dynamics and Properties

Adsorption isotherms, adsorbed layer hydrodynamic thicknesses (from photon correlation spectroscopy), and segment density profiles (from small angle neutron scattering) have been determined as a function of ionic strength for two, narrow-molecular-weight samples of sodium poly(styrene sulfonate) on polystyrene latex particles. Four latices were used, one having a high negative surface charge and three of varying positive surface charge density. The adsorbed amounts are strongly dependent on ionic strength, but not strongly dependent on the polyelectrolyte molecular weight. With increasing surface charge on the positive latex particles, the adsorbed amount decreases. The hydrodynamic thicknesses are relatively small, compared to the values generally found for adsorbed neutral polymers of comparable molecular weight and adsorbed amount. The one exception is with the very low charged (positive) surface, where more extended tails are thought to develop. The hydrodynamic thicknesses on the higher charged positive and negative surfaces are remarkably similar. The segment density profiles, in general, confirm the conclusions reached from the other studies here, that is of generally “flat” configurations on highly charged (positive or negative) surfaces, with relatively short tails, and possibly the development of some loops at high ionic strengths, where intersegmental electrostatic repulsion is suppressed and the polyelectrolyte chains begin to approach the behavior of neutral polymers.